Network Working Group D. Farinacci Internet-Draft V. Fuller Intended status: Experimental D. Meyer Expires: April 14, 2011 D. Lewis cisco Systems October 11, 2010 Locator/ID Separation Protocol (LISP) draft-ietf-lisp-09 Abstract This draft describes a network-based protocol that enables separation of IP addresses into two new numbering spaces: Endpoint Identifiers (EIDs) and Routing Locators (RLOCs). No changes are required to either host protocol stacks or to the "core" of the Internet infrastructure. LISP can be incrementally deployed, without a "flag day", and offers traffic engineering, multi-homing, and mobility benefits even to early adopters, when there are relatively few LISP- capable sites. Design and development of LISP was largely motivated by the problem statement produced by the October, 2006 IAB Routing and Addressing Workshop. Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on April 14, 2011. Farinacci, et al. Expires April 14, 2011 [Page 1] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 Copyright Notice Copyright (c) 2010 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the BSD License. Table of Contents 1. Requirements Notation . . . . . . . . . . . . . . . . . . . . 4 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Definition of Terms . . . . . . . . . . . . . . . . . . . . . 7 4. Basic Overview . . . . . . . . . . . . . . . . . . . . . . . . 12 4.1. Packet Flow Sequence . . . . . . . . . . . . . . . . . . . 14 5. LISP Encapsulation Details . . . . . . . . . . . . . . . . . . 16 5.1. LISP IPv4-in-IPv4 Header Format . . . . . . . . . . . . . 17 5.2. LISP IPv6-in-IPv6 Header Format . . . . . . . . . . . . . 17 5.3. Tunnel Header Field Descriptions . . . . . . . . . . . . . 19 5.4. Dealing with Large Encapsulated Packets . . . . . . . . . 22 5.4.1. A Stateless Solution to MTU Handling . . . . . . . . . 23 5.4.2. A Stateful Solution to MTU Handling . . . . . . . . . 24 5.5. Using Virtualization and Segmentation with LISP . . . . . 24 6. EID-to-RLOC Mapping . . . . . . . . . . . . . . . . . . . . . 26 6.1. LISP IPv4 and IPv6 Control Plane Packet Formats . . . . . 26 6.1.1. LISP Packet Type Allocations . . . . . . . . . . . . . 28 6.1.2. Map-Request Message Format . . . . . . . . . . . . . . 28 6.1.3. EID-to-RLOC UDP Map-Request Message . . . . . . . . . 30 6.1.4. Map-Reply Message Format . . . . . . . . . . . . . . . 32 6.1.5. EID-to-RLOC UDP Map-Reply Message . . . . . . . . . . 35 6.1.6. Map-Register Message Format . . . . . . . . . . . . . 38 6.1.7. Encapsulated Control Message Format . . . . . . . . . 39 6.2. Routing Locator Selection . . . . . . . . . . . . . . . . 41 6.3. Routing Locator Reachability . . . . . . . . . . . . . . . 42 6.3.1. Echo Nonce Algorithm . . . . . . . . . . . . . . . . . 45 6.3.2. RLOC Probing Algorithm . . . . . . . . . . . . . . . . 46 6.4. EID Reachability within a LISP Site . . . . . . . . . . . 47 6.5. Routing Locator Hashing . . . . . . . . . . . . . . . . . 47 6.6. Changing the Contents of EID-to-RLOC Mappings . . . . . . 48 6.6.1. Clock Sweep . . . . . . . . . . . . . . . . . . . . . 49 Farinacci, et al. Expires April 14, 2011 [Page 2] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 6.6.2. Solicit-Map-Request (SMR) . . . . . . . . . . . . . . 49 6.6.3. Database Map Versioning . . . . . . . . . . . . . . . 51 7. Router Performance Considerations . . . . . . . . . . . . . . 52 8. Deployment Scenarios . . . . . . . . . . . . . . . . . . . . . 53 8.1. First-hop/Last-hop Tunnel Routers . . . . . . . . . . . . 54 8.2. Border/Edge Tunnel Routers . . . . . . . . . . . . . . . . 54 8.3. ISP Provider-Edge (PE) Tunnel Routers . . . . . . . . . . 55 8.4. LISP Functionality with Conventional NATs . . . . . . . . 55 9. Traceroute Considerations . . . . . . . . . . . . . . . . . . 56 9.1. IPv6 Traceroute . . . . . . . . . . . . . . . . . . . . . 57 9.2. IPv4 Traceroute . . . . . . . . . . . . . . . . . . . . . 57 9.3. Traceroute using Mixed Locators . . . . . . . . . . . . . 57 10. Mobility Considerations . . . . . . . . . . . . . . . . . . . 59 10.1. Site Mobility . . . . . . . . . . . . . . . . . . . . . . 59 10.2. Slow Endpoint Mobility . . . . . . . . . . . . . . . . . . 59 10.3. Fast Endpoint Mobility . . . . . . . . . . . . . . . . . . 59 10.4. Fast Network Mobility . . . . . . . . . . . . . . . . . . 61 10.5. LISP Mobile Node Mobility . . . . . . . . . . . . . . . . 61 11. Multicast Considerations . . . . . . . . . . . . . . . . . . . 63 12. Security Considerations . . . . . . . . . . . . . . . . . . . 64 13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 65 13.1. LISP Address Type Codes . . . . . . . . . . . . . . . . . 65 13.2. LISP UDP Port Numbers . . . . . . . . . . . . . . . . . . 65 14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 66 14.1. Normative References . . . . . . . . . . . . . . . . . . . 66 14.2. Informative References . . . . . . . . . . . . . . . . . . 67 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 70 Appendix B. Document Change Log . . . . . . . . . . . . . . . . . 71 B.1. Changes to draft-ietf-lisp-09.txt . . . . . . . . . . . . 71 B.2. Changes to draft-ietf-lisp-08.txt . . . . . . . . . . . . 71 B.3. Changes to draft-ietf-lisp-07.txt . . . . . . . . . . . . 73 B.4. Changes to draft-ietf-lisp-06.txt . . . . . . . . . . . . 74 B.5. Changes to draft-ietf-lisp-05.txt . . . . . . . . . . . . 75 B.6. Changes to draft-ietf-lisp-04.txt . . . . . . . . . . . . 76 B.7. Changes to draft-ietf-lisp-03.txt . . . . . . . . . . . . 78 B.8. Changes to draft-ietf-lisp-02.txt . . . . . . . . . . . . 78 B.9. Changes to draft-ietf-lisp-01.txt . . . . . . . . . . . . 78 B.10. Changes to draft-ietf-lisp-00.txt . . . . . . . . . . . . 79 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 80 Farinacci, et al. Expires April 14, 2011 [Page 3] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 1. Requirements Notation The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. Farinacci, et al. Expires April 14, 2011 [Page 4] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 2. Introduction This document describes the Locator/Identifier Separation Protocol (LISP), which provides a set of functions for routers to exchange information used to map from non-routeable Endpoint Identifiers (EIDs) to routeable Routing Locators (RLOCs). It also defines a mechanism for these LISP routers to encapsulate IP packets addressed with EIDs for transmission across an Internet that uses RLOCs for routing and forwarding. Creation of LISP was initially motivated by discussions during the IAB-sponsored Routing and Addressing Workshop held in Amsterdam in October, 2006 (see [RFC4984]). A key conclusion of the workshop was that the Internet routing and addressing system was not scaling well in the face of the explosive growth of new sites; one reason for this poor scaling is the increasing number of multi-homed and other sites that cannot be addressed as part of topologically- or provider-based aggregated prefixes. Additional work that more completely described the problem statement may be found in [RADIR]. A basic observation, made many years ago in early networking research such as that documented in [CHIAPPA] and [RFC4984], is that using a single address field for both identifying a device and for determining where it is topologically located in the network requires optimization along two conflicting axes: for routing to be efficient, the address must be assigned topologically; for collections of devices to be easily and effectively managed, without the need for renumbering in response to topological change (such as that caused by adding or removing attachment points to the network or by mobility events), the address must explicitly not be tied to the topology. The approach that LISP takes to solving the routing scalability problem is to replace IP addresses with two new types of numbers: Routing Locators (RLOCs), which are topologically assigned to network attachment points (and are therefore amenable to aggregation) and used for routing and forwarding of packets through the network; and Endpoint Identifiers (EIDs), which are assigned independently from the network topology, are used for numbering devices, and are aggregated along administrative boundaries. LISP then defines functions for mapping between the two numbering spaces and for encapsulating traffic originated by devices using non-routeable EIDs for transport across a network infrastructure that routes and forwards using RLOCs. Both RLOCs and EIDs are syntactically- identical to IP addresses; it is the semantics of how they are used that differs. This document describes the protocol that implements these functions. The database which stores the mappings between EIDs and RLOCs is Farinacci, et al. Expires April 14, 2011 [Page 5] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 explicitly a separate "module" to facilitate experimentation with a variety of approaches. One database design that is being developed and prototyped as part of the LISP working group work is [ALT]. Others that have been described but not implemented include [CONS], [EMACS], [RPMD], [NERD]. Finally, [LISP-MS], documents a general- purpose service interface for accessing a mapping database; this interface is intended to make the mapping database modular so that different approaches can be tried without the need to modify installed xTRs. Farinacci, et al. Expires April 14, 2011 [Page 6] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 3. Definition of Terms Provider Independent (PI) Addresses: PI addresses are an address block assigned from a pool where blocks are not associated with any particular location in the network (e.g. from a particular service provider), and is therefore not topologically aggregatable in the routing system. Provider Assigned (PA) Addresses: PA addresses are an a address block assigned to a site by each service provider to which a site connects. Typically, each block is sub-block of a service provider Classless Inter-Domain Routing (CIDR) [RFC4632] block and is aggregated into the larger block before being advertised into the global Internet. Traditionally, IP multihoming has been implemented by each multi-homed site acquiring its own, globally- visible prefix. LISP uses only topologically-assigned and aggregatable address blocks for RLOCs, eliminating this demonstrably non-scalable practice. Routing Locator (RLOC): A RLOC is an IPv4 or IPv6 address of an egress tunnel router (ETR). A RLOC is the output of a EID-to-RLOC mapping lookup. An EID maps to one or more RLOCs. Typically, RLOCs are numbered from topologically-aggregatable blocks that are assigned to a site at each point to which it attaches to the global Internet; where the topology is defined by the connectivity of provider networks, RLOCs can be thought of as PA addresses. Multiple RLOCs can be assigned to the same ETR device or to multiple ETR devices at a site. Endpoint ID (EID): An EID is a 32-bit (for IPv4) or 128-bit (for IPv6) value used in the source and destination address fields of the first (most inner) LISP header of a packet. The host obtains a destination EID the same way it obtains an destination address today, for example through a Domain Name System (DNS) [RFC1034] lookup or Session Invitation Protocol (SIP) [RFC3261] exchange. The source EID is obtained via existing mechanisms used to set a host's "local" IP address. An EID is allocated to a host from an EID-prefix block associated with the site where the host is located. An EID can be used by a host to refer to other hosts. EIDs MUST NOT be used as LISP RLOCs. Note that EID blocks may be assigned in a hierarchical manner, independent of the network topology, to facilitate scaling of the mapping database. In addition, an EID block assigned to a site may have site-local structure (subnetting) for routing within the site; this structure is not visible to the global routing system. When used in discussions with other Locator/ID separation proposals, a LISP EID will be called a "LEID". Throughout this document, any references to "EID" refers to an LEID. Farinacci, et al. Expires April 14, 2011 [Page 7] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 EID-prefix: An EID-prefix is a power-of-two block of EIDs which are allocated to a site by an address allocation authority. EID- prefixes are associated with a set of RLOC addresses which make up a "database mapping". EID-prefix allocations can be broken up into smaller blocks when an RLOC set is to be associated with the smaller EID-prefix. A globally routed address block (whether PI or PA) is not an EID-prefix. However, a globally routed address block may be removed from global routing and reused as an EID- prefix. A site that receives an explicitly allocated EID-prefix may not use that EID-prefix as a globally routed prefix assigned to RLOCs. End-system: An end-system is an IPv4 or IPv6 device that originates packets with a single IPv4 or IPv6 header. The end-system supplies an EID value for the destination address field of the IP header when communicating globally (i.e. outside of its routing domain). An end-system can be a host computer, a switch or router device, or any network appliance. Ingress Tunnel Router (ITR): An ITR is a router which accepts an IP packet with a single IP header (more precisely, an IP packet that does not contain a LISP header). The router treats this "inner" IP destination address as an EID and performs an EID-to-RLOC mapping lookup. The router then prepends an "outer" IP header with one of its globally-routable RLOCs in the source address field and the result of the mapping lookup in the destination address field. Note that this destination RLOC may be an intermediate, proxy device that has better knowledge of the EID- to-RLOC mapping closer to the destination EID. In general, an ITR receives IP packets from site end-systems on one side and sends LISP-encapsulated IP packets toward the Internet on the other side. Specifically, when a service provider prepends a LISP header for Traffic Engineering purposes, the router that does this is also regarded as an ITR. The outer RLOC the ISP ITR uses can be based on the outer destination address (the originating ITR's supplied RLOC) or the inner destination address (the originating hosts supplied EID). TE-ITR: A TE-ITR is an ITR that is deployed in a service provider network that prepends an additional LISP header for Traffic Engineering purposes. Egress Tunnel Router (ETR): An ETR is a router that accepts an IP packet where the destination address in the "outer" IP header is one of its own RLOCs. The router strips the "outer" header and forwards the packet based on the next IP header found. In Farinacci, et al. Expires April 14, 2011 [Page 8] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 general, an ETR receives LISP-encapsulated IP packets from the Internet on one side and sends decapsulated IP packets to site end-systems on the other side. ETR functionality does not have to be limited to a router device. A server host can be the endpoint of a LISP tunnel as well. TE-ETR: A TE-ETR is an ETR that is deployed in a service provider network that strips an outer LISP header for Traffic Engineering purposes. xTR: A xTR is a reference to an ITR or ETR when direction of data flow is not part of the context description. xTR refers to the router that is the tunnel endpoint. Used synonymously with the term "Tunnel Router". For example, "An xTR can be located at the Customer Edge (CE) router", meaning both ITR and ETR functionality is at the CE router. EID-to-RLOC Cache: The EID-to-RLOC cache is a short-lived, on- demand table in an ITR that stores, tracks, and is responsible for timing-out and otherwise validating EID-to-RLOC mappings. This cache is distinct from the full "database" of EID-to-RLOC mappings, it is dynamic, local to the ITR(s), and relatively small while the database is distributed, relatively static, and much more global in scope. EID-to-RLOC Database: The EID-to-RLOC database is a global distributed database that contains all known EID-prefix to RLOC mappings. Each potential ETR typically contains a small piece of the database: the EID-to-RLOC mappings for the EID prefixes "behind" the router. These map to one of the router's own, globally-visible, IP addresses. The same database mapping entries MUST be configured on all ETRs for a given site. That is, the EID-prefixes for the site and locator-set for each EID-prefix MUST be the same on all ETRs so they consistently send Map-Reply messages with the same database mapping contents. Recursive Tunneling: Recursive tunneling occurs when a packet has more than one LISP IP header. Additional layers of tunneling may be employed to implement traffic engineering or other re-routing as needed. When this is done, an additional "outer" LISP header is added and the original RLOCs are preserved in the "inner" header. Any references to tunnels in this specification refers to dynamic encapsulating tunnels and never are they statically configured. Farinacci, et al. Expires April 14, 2011 [Page 9] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 Reencapsulating Tunnels: Reencapsulating tunneling occurs when a packet has no more than one LISP IP header (two IP headers total) and when it needs to be diverted to new RLOC, an ETR can decapsulate the packet (remove the LISP header) and prepends a new tunnel header, with new RLOC, on to the packet. Doing this allows a packet to be re-routed by the re-encapsulating router without adding the overhead of additional tunnel headers. Any references to tunnels in this specification refers to dynamic encapsulating tunnels and never are they statically configured. LISP Header: a term used in this document to refer to the outer IPv4 or IPv6 header, a UDP header, and a LISP-specific 8-byte header that follows the UDP header, an ITR prepends or an ETR strips. Address Family Identifier (AFI): a term used to describe an address encoding in a packet. An address family currently pertains to an IPv4 or IPv6 address. See [AFI] and [RFC1700] for details. An AFI value of 0 used in this specification indicates an unspecified encoded address where the length of the address is 0 bytes following the 16-bit AFI value of 0. Negative Mapping Entry: A negative mapping entry, also known as a negative cache entry, is an EID-to-RLOC entry where an EID-prefix is advertised or stored with no RLOCs. That is, the locator-set for the EID-to-RLOC entry is empty or has an encoded locator count of 0. This type of entry could be used to describe a prefix from a non-LISP site, which is explicitly not in the mapping database. There are a set of well defined actions that are encoded in a Negative Map-Reply. Data Probe: A data-probe is a LISP-encapsulated data packet where the inner header destination address equals the outer header destination address used to trigger a Map-Reply by a decapsulating ETR. In addition, the original packet is decapsulated and delivered to the destination host. A Data Probe is used in some of the mapping database designs to "probe" or request a Map-Reply from an ETR; in other cases, Map-Requests are used. See each mapping database design for details. Proxy ITR (PITR): A PITR is also known as a PTR is defined and described in [INTERWORK], a PITR acts like an ITR but does so on behalf of non-LISP sites which send packets to destinations at LISP sites. Farinacci, et al. Expires April 14, 2011 [Page 10] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 Proxy ETR (PETR): A PETR is defined and described in [INTERWORK], a PETR acts like an ETR but does so on behalf of LISP sites which send packets to destinations at non-LISP sites. Route-returnability: is an assumption that the underlying routing system will deliver packets to the destination. When combined with a nonce that is provided by a sender and returned by a receiver limits off-path data insertion. LISP site: is a set of routers in an edge network that are under a single technical administration. LISP routers which reside in the edge network are the demarcation points to separate the edge network from the core network. Client-side: a term used in this document to indicate a connection initiation attempt by an EID. The ITR(s) at the LISP site are the first to get involved in obtaining database map cache entries by sending Map-Request messages. Server-side: a term used in this document to indicate a connection initiation attempt is being accepted for a destination EID. The ETR(s) at the destination LISP site are the first to send Map- Replies to the source site initiating the connection. The ETR(s) at this destination site can obtain mappings by gleaning information from Map-Requests, Data-Probes, or encapsulated packets. Farinacci, et al. Expires April 14, 2011 [Page 11] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 4. Basic Overview One key concept of LISP is that end-systems (hosts) operate the same way they do today. The IP addresses that hosts use for tracking sockets, connections, and for sending and receiving packets do not change. In LISP terminology, these IP addresses are called Endpoint Identifiers (EIDs). Routers continue to forward packets based on IP destination addresses. When a packet is LISP encapsulated, these addresses are referred to as Routing Locators (RLOCs). Most routers along a path between two hosts will not change; they continue to perform routing/ forwarding lookups on the destination addresses. For routers between the source host and the ITR as well as routers from the ETR to the destination host, the destination address is an EID. For the routers between the ITR and the ETR, the destination address is an RLOC. Another key LISP concept is the "Tunnel Router". A tunnel router prepends LISP headers on host-originated packets and strip them prior to final delivery to their destination. The IP addresses in this "outer header" are RLOCs. During end-to-end packet exchange between two Internet hosts, an ITR prepends a new LISP header to each packet and an egress tunnel router strips the new header. The ITR performs EID-to-RLOC lookups to determine the routing path to the ETR, which has the RLOC as one of its IP addresses. Some basic rules governing LISP are: o End-systems (hosts) only send to addresses which are EIDs. They don't know addresses are EIDs versus RLOCs but assume packets get to LISP routers, which in turn, deliver packets to the destination the end-system has specified. o EIDs are always IP addresses assigned to hosts. o LISP routers mostly deal with Routing Locator addresses. See details later in Section 4.1 to clarify what is meant by "mostly". o RLOCs are always IP addresses assigned to routers; preferably, topologically-oriented addresses from provider CIDR blocks. o When a router originates packets it may use as a source address either an EID or RLOC. When acting as a host (e.g. when terminating a transport session such as SSH, TELNET, or SNMP), it may use an EID that is explicitly assigned for that purpose. An EID that identifies the router as a host MUST NOT be used as an RLOC; an EID is only routable within the scope of a site. A typical BGP configuration might demonstrate this "hybrid" EID/RLOC Farinacci, et al. Expires April 14, 2011 [Page 12] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 usage where a router could use its "host-like" EID to terminate iBGP sessions to other routers in a site while at the same time using RLOCs to terminate eBGP sessions to routers outside the site. o EIDs are not expected to be usable for global end-to-end communication in the absence of an EID-to-RLOC mapping operation. They are expected to be used locally for intra-site communication. o EID prefixes are likely to be hierarchically assigned in a manner which is optimized for administrative convenience and to facilitate scaling of the EID-to-RLOC mapping database. The hierarchy is based on a address allocation hierarchy which is independent of the network topology. o EIDs may also be structured (subnetted) in a manner suitable for local routing within an autonomous system. An additional LISP header may be prepended to packets by a TE-ITR when re-routing of the path for a packet is desired. An obvious instance of this would be an ISP router that needs to perform traffic engineering for packets flowing through its network. In such a situation, termed Recursive Tunneling, an ISP transit acts as an additional ingress tunnel router and the RLOC it uses for the new prepended header would be either a TE-ETR within the ISP (along intra-ISP traffic engineered path) or a TE-ETR within another ISP (an inter-ISP traffic engineered path, where an agreement to build such a path exists). In order to avoid excessive packet overhead as well as possible encapsulation loops, this document mandates that a maximum of two LISP headers can be prepended to a packet. It is believed two headers is sufficient, where the first prepended header is used at a site for Location/Identity separation and second prepended header is used inside a service provider for Traffic Engineering purposes. Tunnel Routers can be placed fairly flexibly in a multi-AS topology. For example, the ITR for a particular end-to-end packet exchange might be the first-hop or default router within a site for the source host. Similarly, the egress tunnel router might be the last-hop router directly-connected to the destination host. Another example, perhaps for a VPN service out-sourced to an ISP by a site, the ITR could be the site's border router at the service provider attachment point. Mixing and matching of site-operated, ISP-operated, and other tunnel routers is allowed for maximum flexibility. See Section 8 for more details. Farinacci, et al. Expires April 14, 2011 [Page 13] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 4.1. Packet Flow Sequence This section provides an example of the unicast packet flow with the following conditions: o Source host "host1.abc.com" is sending a packet to "host2.xyz.com", exactly what host1 would do if the site was not using LISP. o Each site is multi-homed, so each tunnel router has an address (RLOC) assigned from the service provider address block for each provider to which that particular tunnel router is attached. o The ITR(s) and ETR(s) are directly connected to the source and destination, respectively, but the source and destination can be located anywhere in LISP site. o Map-Requests can be sent on the underlying routing system topology or over an alternative topology [ALT]. o Map-Replies are sent on the underlying routing system topology. Client host1.abc.com wants to communicate with server host2.xyz.com: 1. host1.abc.com wants to open a TCP connection to host2.xyz.com. It does a DNS lookup on host2.xyz.com. An A/AAAA record is returned. This address is the destination EID. The locally- assigned address of host1.abc.com is used as the source EID. An IPv4 or IPv6 packet is built and forwarded through the LISP site as a normal IP packet until it reaches a LISP ITR. 2. The LISP ITR must be able to map the EID destination to an RLOC of one of the ETRs at the destination site. The specific method used to do this is not described in this example. See [ALT] or [CONS] for possible solutions. 3. The ITR will send a LISP Map-Request. Map-Requests SHOULD be rate-limited. 4. When an alternate mapping system is not in use, the Map-Request packet is routed through the underlying routing system. Otherwise, the Map-Request packet is routed on an alternate logical topology. In either case, when the Map-Request arrives at one of the ETRs at the destination site, it will process the packet as a control message. 5. The ETR looks at the destination EID of the Map-Request and matches it against the prefixes in the ETR's configured EID-to- Farinacci, et al. Expires April 14, 2011 [Page 14] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 RLOC mapping database. This is the list of EID-prefixes the ETR is supporting for the site it resides in. If there is no match, the Map-Request is dropped. Otherwise, a LISP Map-Reply is returned to the ITR. 6. The ITR receives the Map-Reply message, parses the message (to check for format validity) and stores the mapping information from the packet. This information is stored in the ITR's EID-to- RLOC mapping cache. Note that the map cache is an on-demand cache. An ITR will manage its map cache in such a way that optimizes for its resource constraints. 7. Subsequent packets from host1.abc.com to host2.xyz.com will have a LISP header prepended by the ITR using the appropriate RLOC as the LISP header destination address learned from the ETR. Note the packet may be sent to a different ETR than the one which returned the Map-Reply due to the source site's hashing policy or the destination site's locator-set policy. 8. The ETR receives these packets directly (since the destination address is one of its assigned IP addresses), strips the LISP header and forwards the packets to the attached destination host. In order to eliminate the need for a mapping lookup in the reverse direction, an ETR MAY create a cache entry that maps the source EID (inner header source IP address) to the source RLOC (outer header source IP address) in a received LISP packet. Such a cache entry is termed a "gleaned" mapping and only contains a single RLOC for the EID in question. More complete information about additional RLOCs SHOULD be verified by sending a LISP Map-Request for that EID. Both ITR and the ETR may also influence the decision the other makes in selecting an RLOC. See Section 6 for more details. Farinacci, et al. Expires April 14, 2011 [Page 15] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 5. LISP Encapsulation Details Since additional tunnel headers are prepended, the packet becomes larger and can exceed the MTU of any link traversed from the ITR to the ETR. It is recommended in IPv4 that packets do not get fragmented as they are encapsulated by the ITR. Instead, the packet is dropped and an ICMP Too Big message is returned to the source. This specification recommends that implementations support for one of the proposed fragmentation and reassembly schemes. These two simple existing schemes are detailed in Section 5.4. Farinacci, et al. Expires April 14, 2011 [Page 16] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 5.1. LISP IPv4-in-IPv4 Header Format 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / |Version| IHL |Type of Service| Total Length | / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | Identification |Flags| Fragment Offset | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ OH | Time to Live | Protocol = 17 | Header Checksum | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | Source Routing Locator | \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \ | Destination Routing Locator | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / | Source Port = xxxx | Dest Port = 4341 | UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \ | UDP Length | UDP Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ L |N|L|E|V|I|flags| Nonce/Map-Version | I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ S / | Instance ID/Locator Status Bits | P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / |Version| IHL |Type of Service| Total Length | / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | Identification |Flags| Fragment Offset | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ IH | Time to Live | Protocol | Header Checksum | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | Source EID | \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \ | Destination EID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 5.2. LISP IPv6-in-IPv6 Header Format 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / |Version| Traffic Class | Flow Label | / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Farinacci, et al. Expires April 14, 2011 [Page 17] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 | | Payload Length | Next Header=17| Hop Limit | v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | O + + u | | t + Source Routing Locator + e | | r + + | | H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ d | | r + + | | ^ + Destination Routing Locator + | | | \ + + \ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / | Source Port = xxxx | Dest Port = 4341 | UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \ | UDP Length | UDP Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ L |N|L|E|V|I|flags| Nonce/Map-Version | I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ S / | Instance ID/Locator Status Bits | P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / |Version| Traffic Class | Flow Label | / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / | Payload Length | Next Header | Hop Limit | v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | I + + n | | n + Source EID + e | | r + + | | H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ d | | r + + | | ^ + Destination EID + \ | | \ + + \ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Farinacci, et al. Expires April 14, 2011 [Page 18] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 5.3. Tunnel Header Field Descriptions Inner Header: The inner header is the header on the datagram received from the originating host. The source and destination IP addresses are EIDs. Outer Header: The outer header is a new header prepended by an ITR. The address fields contain RLOCs obtained from the ingress router's EID-to-RLOC cache. The IP protocol number is "UDP (17)" from [RFC0768]. The DF bit of the Flags field is set to 0 when the method in Section 5.4.1 is used and set to 1 when the method in Section 5.4.2 is used. UDP Header: The UDP header contains a ITR selected source port when encapsulating a packet. See Section 6.5 for details on the hash algorithm used to select a source port based on the 5-tuple of the inner header. The destination port MUST be set to the well-known IANA assigned port value 4341. UDP Checksum: The UDP checksum field SHOULD be transmitted as zero by an ITR for either IPv4 [RFC0768] or IPv6 encapsulation [UDP-TUNNELS]. When a packet with a zero UDP checksum is received by an ETR, the ETR MUST accept the packet for decapsulation. When an ITR transmits a non-zero value for the UDP checksum, it MUST send a correctly computed value in this field. When an ETR receives a packet with a non-zero UDP checksum, it MAY choose to verify the checksum value. If it chooses to perform such verification, and the verification fails, the packet MUST be silently dropped. If the ETR chooses not to perform the verification, or performs the verification successfully, the packet MUST be accepted for decapsulation. The handling of UDP checksums for all tunneling protocols, including LISP, is under active discussion within the IETF. When that discussion concludes, any necessary changes will be made to align LISP with the outcome of the broader discussion. UDP Length: The UDP length field is for an IPv4 encapsulated packet, the inner header Total Length plus the UDP and LISP header lengths are used. For an IPv6 encapsulated packet, the inner header Payload Length plus the size of the IPv6 header (40 bytes) plus the size of the UDP and LISP headers are used. The UDP header length is 8 bytes. N: The N bit is the nonce-present bit. When this bit is set to 1, the low-order 24-bits of the first 32-bits of the LISP header contains a Nonce. See Section 6.3.1 for details. Both N and V bits MUST NOT be set in the same packet. If they are, a decapsulating ETR MUST treat the "Nonce/Map-Version" field as Farinacci, et al. Expires April 14, 2011 [Page 19] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 having a Nonce value present. L: The L bit is the Locator-Status-Bits field enabled bit. When this bit is set to 1, the Locator-Status-Bits in the second 32-bits of the LISP header are in use. x 1 x x 0 x x x +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |N|L|E|V|I|flags| Nonce/Map-Version | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Locator Status Bits | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ E: The E bit is the echo-nonce-request bit. When this bit is set to 1, the N bit MUST be 1. This bit SHOULD be ignored and has no meaning when the N bit is set to 0. See Section 6.3.1 for details. V: The V bit is the Map-Version present bit. When this bit is set to 1, the N bit MUST be 0. Refer to Section 6.6.3 for more details. This bit indicates that the first 4 bytes of the LISP header is encoded as: 0 x 0 1 x x x x +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |N|L|E|V|I|flags| Source Map-Version | Dest Map-Version | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Instance ID/Locator Status Bits | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ I: The I bit is the Instance ID bit. See Section 5.5 for more details. When this bit is set to 1, the Locator Status Bits field is reduced to 8-bits and the high-order 24-bits are used as an Instance ID. If the L-bit is set to 0, then the low-order 8 bits are transmitted as zero and ignored on receipt. The format of the last 4 bytes of the LISP header would look like: Farinacci, et al. Expires April 14, 2011 [Page 20] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 x x x x 1 x x x +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |N|L|E|V|I|flags| Nonce/Map-Version | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Instance ID | LSBs | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ flags: The flags field is a 3-bit field is reserved for future flag use. It is set to 0 on transmit and ignored on receipt. LISP Nonce: The LISP nonce field is a 24-bit value that is randomly generated by an ITR when the N-bit is set to 1. The nonce is also used when the E-bit is set to request the nonce value to be echoed by the other side when packets are returned. When the E-bit is clear but the N-bit is set, a remote ITR is either echoing a previously requested echo-nonce or providing a random nonce. See Section 6.3.1 for more details. LISP Locator Status Bits: The locator status bits field in the LISP header is set by an ITR to indicate to an ETR the up/down status of the Locators in the source site. Each RLOC in a Map-Reply is assigned an ordinal value from 0 to n-1 (when there are n RLOCs in a mapping entry). The Locator Status Bits are numbered from 0 to n-1 from the least significant bit of field. The field is 32-bits when the I-bit is set to 0 and is 8 bits when the I-bit is set to 1. When a Locator Status Bit is set to 1, the ITR is indicating to the ETR the RLOC associated with the bit ordinal has up status. See Section 6.3 for details on how an ITR can determine the status of other ITRs at the same site. When a site has multiple EID- prefixes which result in multiple mappings (where each could have a different locator-set), the Locator Status Bits setting in an encapsulated packet MUST reflect the mapping for the EID-prefix that the inner-header source EID address matches. When doing ITR/PITR encapsulation: o The outer header Time to Live field (or Hop Limit field, in case of IPv6) SHOULD be copied from the inner header Time to Live field. o The outer header Type of Service field (or the Traffic Class field, in the case of IPv6) SHOULD be copied from the inner header Type of Service field (with one caveat, see below). When doing ETR/PETR decapsulation: Farinacci, et al. Expires April 14, 2011 [Page 21] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 o The inner header Time to Live field (or Hop Limit field, in case of IPv6) SHOULD be copied from the outer header Time to Live field, when the Time to Live field of the outer header is less than the Time to Live of the inner header. Failing to perform this check can cause the Time to Live of the inner header to increment across encapsulation/decapsulation cycle. This check is also performed when doing initial encapsulation when a packet comes to an ITR or PITR destined for a LISP site. o The inner header Type of Service field (or the Traffic Class field, in the case of IPv6) SHOULD be copied from the outer header Type of Service field (with one caveat, see below). Note if an ETR/PETR is also an ITR/PITR and choose to reencapsulate after decapsulating, the net effect of this is that the new outer header will carry the same Time to Live as the old outer header. Copying the TTL serves two purposes: first, it preserves the distance the host intended the packet to travel; second, and more importantly, it provides for suppression of looping packets in the event there is a loop of concatenated tunnels due to misconfiguration. See Section 9.3 for TTL exception handling for traceroute packets. The ECN field occupies bits 6 and 7 of both the IPv4 Type of Service field and the IPv6 Traffic Class field [RFC3168]. The ECN field requires special treatment in order to avoid discarding indications of congestion [RFC3168]. ITR encapsulation MUST copy the 2-bit ECN field from the inner header to the outer header. Re-encapsulation MUST copy the 2-bit ECN field from the stripped outer header to the new outer header. If the ECN field contains a congestion indication codepoint (the value is '11', the Congestion Experienced (CE) codepoint), then ETR decapsulation MUST copy the 2-bit ECN field from the stripped outer header to the surviving inner header that is used to forward the packet beyond the ETR. These requirements preserve Congestion Experienced (CE) indications when a packet that uses ECN traverses a LISP tunnel and becomes marked with a CE indication due to congestion between the tunnel endpoints. 5.4. Dealing with Large Encapsulated Packets This section proposes two simple mechanisms to deal with packets that exceed the path MTU between the ITR and ETR. It is left to the implementor to decide if the stateless or stateful mechanism should be implemented. Both or neither can be used since it is a local decision in the ITR regarding how to deal with MTU issues, and sites can interoperate with differing mechanisms. Farinacci, et al. Expires April 14, 2011 [Page 22] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 Both stateless and stateful mechanisms also apply to Reencapsulating and Recursive Tunneling. So any actions below referring to an ITR also apply to an TE-ITR. 5.4.1. A Stateless Solution to MTU Handling An ITR stateless solution to handle MTU issues is described as follows: 1. Define an architectural constant S for the maximum size of a packet, in bytes, an ITR would like to receive from a source inside of its site. 2. Define L to be the maximum size, in bytes, a packet of size S would be after the ITR prepends the LISP header, UDP header, and outer network layer header of size H. 3. Calculate: S + H = L. When an ITR receives a packet from a site-facing interface and adds H bytes worth of encapsulation to yield a packet size greater than L bytes, it resolves the MTU issue by first splitting the original packet into 2 equal-sized fragments. A LISP header is then prepended to each fragment. The size of the encapsulated fragments is then (S/2 + H), which is less than the ITR's estimate of the path MTU between the ITR and its correspondent ETR. When an ETR receives encapsulated fragments, it treats them as two individually encapsulated packets. It strips the LISP headers then forwards each fragment to the destination host of the destination site. The two fragments are reassembled at the destination host into the single IP datagram that was originated by the source host. This behavior is performed by the ITR when the source host originates a packet with the DF field of the IP header is set to 0. When the DF field of the IP header is set to 1, or the packet is an IPv6 packet originated by the source host, the ITR will drop the packet when the size is greater than L, and sends an ICMP Too Big message to the source with a value of S, where S is (L - H). When the outer header encapsulation uses an IPv4 header, an implementation SHOULD set the DF bit to 1 so ETR fragment reassembly can be avoided. An implementation MAY set the DF bit in such headers to 0 if it has good reason to believe there are unresolvable path MTU issues between the sending ITR and the receiving ETR. This specification recommends that L be defined as 1500. Farinacci, et al. Expires April 14, 2011 [Page 23] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 5.4.2. A Stateful Solution to MTU Handling An ITR stateful solution to handle MTU issues is described as follows and was first introduced in [OPENLISP]: 1. The ITR will keep state of the effective MTU for each locator per mapping cache entry. The effective MTU is what the core network can deliver along the path between ITR and ETR. 2. When an IPv6 encapsulated packet or an IPv4 encapsulated packet with DF bit set to 1, exceeds what the core network can deliver, one of the intermediate routers on the path will send an ICMP Too Big message to the ITR. The ITR will parse the ICMP message to determine which locator is affected by the effective MTU change and then record the new effective MTU value in the mapping cache entry. 3. When a packet is received by the ITR from a source inside of the site and the size of the packet is greater than the effective MTU stored with the mapping cache entry associated with the destination EID the packet is for, the ITR will send an ICMP Too Big message back to the source. The packet size advertised by the ITR in the ICMP Too Big message is the effective MTU minus the LISP encapsulation length. Even though this mechanism is stateful, it has advantages over the stateless IP fragmentation mechanism, by not involving the destination host with reassembly of ITR fragmented packets. 5.5. Using Virtualization and Segmentation with LISP When multiple organizations inside of a LISP site are using private addresses [RFC1918] as EID-prefixes, their address spaces MUST remain segregated due to possible address duplication. An Instance ID in the address encoding can aid in making the entire AFI based address unique. See IANA Considerations Section 13.1 for details for possible address encodings. An Instance ID can be carried in a LISP encapsulated packet. An ITR that prepends a LISP header, will copy a 24-bit value, used by the LISP router to uniquely identify the address space. The value is copied to the Instance ID field of the LISP header and the I-bit is set to 1. When an ETR decapsulates a packet, the Instance ID from the LISP header is used as a table identifier to locate the forwarding table to use for the inner destination EID lookup. Farinacci, et al. Expires April 14, 2011 [Page 24] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 For example, a 802.1Q VLAN tag or VPN identifier could be used as a 24-bit Instance ID. Farinacci, et al. Expires April 14, 2011 [Page 25] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 6. EID-to-RLOC Mapping 6.1. LISP IPv4 and IPv6 Control Plane Packet Formats The following new UDP packet types are used to retrieve EID-to-RLOC mappings: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Version| IHL |Type of Service| Total Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Identification |Flags| Fragment Offset | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Time to Live | Protocol = 17 | Header Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Source Routing Locator | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Destination Routing Locator | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / | Source Port | Dest Port | UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \ | UDP Length | UDP Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | LISP Message | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Version| Traffic Class | Flow Label | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Payload Length | Next Header=17| Hop Limit | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Source Routing Locator + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + Farinacci, et al. Expires April 14, 2011 [Page 26] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 | | + Destination Routing Locator + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / | Source Port | Dest Port | UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \ | UDP Length | UDP Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | LISP Message | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The LISP UDP-based messages are the Map-Request and Map-Reply messages. When a UDP Map-Request is sent, the UDP source port is chosen by the sender and the destination UDP port number is set to 4342. When a UDP Map-Reply is sent, the source UDP port number is set to 4342 and the destination UDP port number is copied from the source port of either the Map-Request or the invoking data packet. Implementations MUST be prepared to accept packets when either the source port or destination UDP port is set to 4342 due to NATs changing port number values. The UDP Length field will reflect the length of the UDP header and the LISP Message payload. The UDP Checksum is computed and set to non-zero for Map-Request, Map-Reply, Map-Register and ECM control messages. It MUST be checked on receipt and if the checksum fails, the packet MUST be dropped. LISP-CONS [CONS] uses TCP to send LISP control messages. The format of control messages includes the UDP header so the checksum and length fields can be used to protect and delimit message boundaries. This main LISP specification is the authoritative source for message format definitions for the Map-Request and Map-Reply messages. Farinacci, et al. Expires April 14, 2011 [Page 27] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 6.1.1. LISP Packet Type Allocations This section will be the authoritative source for allocating LISP Type values. Current allocations are: Reserved: 0 b'0000' LISP Map-Request: 1 b'0001' LISP Map-Reply: 2 b'0010' LISP Map-Register: 3 b'0011' LISP Encapsulated Control Message: 8 b'1000' 6.1.2. Map-Request Message Format 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Type=1 |A|M|P|S| Reserved | IRC | Record Count | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Nonce . . . | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | . . . Nonce | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Source-EID-AFI | Source EID Address ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ITR-RLOC-AFI 1 | ITR-RLOC Address 1 ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ITR-RLOC-AFI n | ITR-RLOC Address n ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / | Reserved | EID mask-len | EID-prefix-AFI | Rec +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \ | EID-prefix ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Map-Reply Record ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Mapping Protocol Data | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Packet field descriptions: Farinacci, et al. Expires April 14, 2011 [Page 28] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 Type: 1 (Map-Request) A: This is an authoritative bit, which is set to 0 for UDP-based Map- Requests sent by an ITR. M: When set, it indicates a Map-Reply Record segment is included in the Map-Request. P: This is the probe-bit which indicates that a Map-Request SHOULD be treated as a locator reachability probe. The receiver SHOULD respond with a Map-Reply with the probe-bit set, indicating the Map-Reply is a locator reachability probe reply, with the nonce copied from the Map-Request. See Section 6.3.2 for more details. S: This is the SMR bit. See Section 6.6.2 for details. Reserved: Set to 0 on transmission and ignored on receipt. IRC: This 5-bit field is the ITR-RLOC Count which encodes the additional number of (ITR-RLOC-AFI, ITR-RLOC Address) fields present in this message. At least one (ITR-RLOC-AFI, ITR-RLOC- Address) pair must always be encoded. Multiple ITR-RLOC Address fields are used so a Map-Replier can select which destination address to use for a Map-Reply. The IRC value ranges from 0 to 31, and for a value of 1, there are 2 ITR-RLOC addresses encoded and so on up to 31 which encodes a total of 32 ITR-RLOC addresses. Record Count: The number of records in this Map-Request message. A record is comprised of the portion of the packet that is labeled 'Rec' above and occurs the number of times equal to Record Count. For this version of the protocol, a receiver MUST accept and process Map-Requests that contain one or more records, but a sender MUST only send Map-Requests containing one record. Support for requesting multiple EIDs in a single Map-Request message will be specified in a future version of the protocol. Nonce: An 8-byte random value created by the sender of the Map- Request. This nonce will be returned in the Map-Reply. The security of the LISP mapping protocol depends critically on the strength of the nonce in the Map-Request message. The nonce SHOULD be generated by a properly seeded pseudo-random (or strong random) source. See [RFC4086] for advice on generating security- sensitive random data. Source-EID-AFI: Address family of the "Source EID Address" field. Farinacci, et al. Expires April 14, 2011 [Page 29] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 Source EID Address: This is the EID of the source host which originated the packet which is invoking this Map-Request. When Map-Requests are used for refreshing a map-cache entry or for RLOC-probing, an AFI value 0 is used and this field is of zero length. ITR-RLOC-AFI: Address family of the "ITR-RLOC Address" field that follows this field. ITR-RLOC Address: Used to give the ETR the option of selecting the destination address from any address family for the Map-Reply message. This address MUST be a routable RLOC address of the sender of the Map-Request message. EID mask-len: Mask length for EID prefix. EID-prefix-AFI: Address family of EID-prefix according to [RFC5226] EID-prefix: 4 bytes if an IPv4 address-family, 16 bytes if an IPv6 address-family. When a Map-Request is sent by an ITR because a data packet is received for a destination where there is no mapping entry, the EID-prefix is set to the destination IP address of the data packet. And the 'EID mask-len' is set to 32 or 128 for IPv4 or IPv6, respectively. When an xTR wants to query a site about the status of a mapping it already has cached, the EID- prefix used in the Map-Request has the same mask-length as the EID-prefix returned from the site when it sent a Map-Reply message. Map-Reply Record: When the M bit is set, this field is the size of a single "Record" in the Map-Reply format. This Map-Reply record contains the EID-to-RLOC mapping entry associated with the Source EID. This allows the ETR which will receive this Map-Request to cache the data if it chooses to do so. Mapping Protocol Data: See [CONS] for details. This field is optional and present when the UDP length indicates there is enough space in the packet to include it. 6.1.3. EID-to-RLOC UDP Map-Request Message A Map-Request is sent from an ITR when it needs a mapping for an EID, wants to test an RLOC for reachability, or wants to refresh a mapping before TTL expiration. For the initial case, the destination IP address used for the Map-Request is the destination-EID from the packet which had a mapping cache lookup failure. For the latter 2 cases, the destination IP address used for the Map-Request is one of the RLOC addresses from the locator-set of the map cache entry. The Farinacci, et al. Expires April 14, 2011 [Page 30] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 source address is either an IPv4 or IPv6 RLOC address depending if the Map-Request is using an IPv4 versus IPv6 header, respectively. In all cases, the UDP source port number for the Map-Request message is an ITR/PITR selected 16-bit value and the UDP destination port number is set to the well-known destination port number 4342. A successful Map-Reply updates the cached set of RLOCs associated with the EID prefix range. One or more Map-Request (ITR-RLOC-AFI, ITR-RLOC-Address) fields MUST be filled in by the ITR. The number of fields (minus 1) encoded MUST be placed in the IRC field. The ITR MAY include all locally configured locators in this list or just provide one locator address from each address family it supports. If the ITR erroneously provides no ITR-RLOC addresses, the Map-Replier MUST drop the Map- Request. Map-Requests can also be LISP encapsulated using UDP destination port 4342 with a LISP type value set to "Encapsulated Control Message", when sent from an ITR to a Map-Resolver. Likewise, Map-Requests are LISP encapsulated the same way from a Map-Server to an ETR. Details on encapsulated Map-Requests and Map-Resolvers can be found in [LISP-MS]. Map-Requests MUST be rate-limited. It is recommended that a Map- Request for the same EID-prefix be sent no more than once per second. An ITR that is configured with mapping database information (i.e. it is also an ETR) may optionally include those mappings in a Map- Request. When an ETR configured to accept and verify such "piggybacked" mapping data receives such a Map-Request and it does not have this mapping in the map-cache, it may originate a "verifying Map-Request", addressed to the map-requesting ITR. If the ETR has a map-cache entry that matches the "piggybacked" EID and the RLOC is in the locator-set for the entry, then it may send the "verifying Map- Request" directly to the originating Map-Request source. If the RLOC is not in the locator-set, then the ETR MUST send the "verifying Map- Request" to the "piggybacked" EID. Doing this forces the "verifying Map-Request" to go through the mapping database system to reach the authoritative source of information about that EID, guarding against RLOC-spoofing in in the "piggybacked" mapping data. Farinacci, et al. Expires April 14, 2011 [Page 31] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 6.1.4. Map-Reply Message Format 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Type=2 |P|E| Reserved | Record Count | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Nonce . . . | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | . . . Nonce | +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | Record TTL | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ R | Locator Count | EID mask-len | ACT |A| Reserved | e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ c | Rsvd | Map-Version Number | EID-AFI | o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ r | EID-prefix | d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | /| Priority | Weight | M Priority | M Weight | | L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | o | Unused Flags |L|p|R| Loc-AFI | | c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | \| Locator | +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Mapping Protocol Data | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Packet field descriptions: Type: 2 (Map-Reply) P: This is the probe-bit which indicates that the Map-Reply is in response to a locator reachability probe Map-Request. The nonce field MUST contain a copy of the nonce value from the original Map-Request. See Section 6.3.2 for more details. E: Indicates that the ETR which sends this Map-Reply message is advertising that the site is enabled for the Echo-Nonce locator reachability algorithm. See Section 6.3.1 for more details. Reserved: Set to 0 on transmission and ignored on receipt. Farinacci, et al. Expires April 14, 2011 [Page 32] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 Record Count: The number of records in this reply message. A record is comprised of that portion of the packet labeled 'Record' above and occurs the number of times equal to Record count. Nonce: A 24-bit value set in a Data-Probe packet or a 64-bit value from the Map-Request is echoed in this Nonce field of the Map- Reply. Record TTL: The time in minutes the recipient of the Map-Reply will store the mapping. If the TTL is 0, the entry SHOULD be removed from the cache immediately. If the value is 0xffffffff, the recipient can decide locally how long to store the mapping. Locator Count: The number of Locator entries. A locator entry comprises what is labeled above as 'Loc'. The locator count can be 0 indicating there are no locators for the EID-prefix. EID mask-len: Mask length for EID prefix. ACT: This 3-bit field describes negative Map-Reply actions. These bits are used only when the 'Locator Count' field is set to 0. The action bits are encoded only in Map-Reply messages. The actions defined are used by an ITR or PTR when a destination EID matches a negative mapping cache entry. Unassigned values should cause a map-cache entry to be created and, when packets match this negative cache entry, they will be dropped. The current assigned values are: (0) No-Action: The map-cache is kept alive and packet encapsulation occurs. (1) Natively-Forward: The packet is not encapsulated or dropped but natively forwarded. (2) Send-Map-Request: The packet invokes sending a Map-Request. (3) Drop: A packet that matches this map-cache entry is dropped. A: The Authoritative bit, when sent by a UDP-based message is always set to 1 by an ETR. See [CONS] for TCP-based Map-Replies. When a Map-Server is proxy Map-Replying [LISP-MS] for a LISP site, the Authoritative bit is set to 0. This indicates to requesting ITRs that the Map-Reply was not originated by a LISP node managed at the site that owns the EID-prefix. Farinacci, et al. Expires April 14, 2011 [Page 33] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 Map-Version Number: When this 12-bit value is non-zero the Map-Reply sender is informing the ITR what the version number is for the EID-record contained in the Map-Reply. The ETR can allocate this number internally but MUST coordinate this value with other ETRs for the site. When this value is 0, there is no versioning information conveyed. The Map-Version Number can be included in Map-Request and Map-Register messages. See Section 6.6.3 for more details. EID-AFI: Address family of EID-prefix according to [RFC5226]. EID-prefix: 4 bytes if an IPv4 address-family, 16 bytes if an IPv6 address-family. Priority: each RLOC is assigned a unicast priority. Lower values are more preferable. When multiple RLOCs have the same priority, they may be used in a load-split fashion. A value of 255 means the RLOC MUST NOT be used for unicast forwarding. Weight: when priorities are the same for multiple RLOCs, the weight indicates how to balance unicast traffic between them. Weight is encoded as a relative weight of total unicast packets that match the mapping entry. If a non-zero weight value is used for any RLOC, then all RLOCs MUST use a non-zero weight value and then the sum of all weight values MUST equal 100. If a zero value is used for any RLOC weight, then all weights MUST be zero and the receiver of the Map-Reply will decide how to load-split traffic. See Section 6.5 for a suggested hash algorithm to distribute load across locators with same priority and equal weight values. M Priority: each RLOC is assigned a multicast priority used by an ETR in a receiver multicast site to select an ITR in a source multicast site for building multicast distribution trees. A value of 255 means the RLOC MUST NOT be used for joining a multicast distribution tree. M Weight: when priorities are the same for multiple RLOCs, the weight indicates how to balance building multicast distribution trees across multiple ITRs. The weight is encoded as a relative weight of total number of trees built to the source site identified by the EID-prefix. If a non-zero weight value is used for any RLOC, then all RLOCs MUST use a non-zero weight value and then the sum of all weight values MUST equal 100. If a zero value is used for any RLOC weight, then all weights MUST be zero and the receiver of the Map-Reply will decide how to distribute multicast state across ITRs. Farinacci, et al. Expires April 14, 2011 [Page 34] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 Unused Flags: set to 0 when sending and ignored on receipt. L: when this bit is set, the locator is flagged as a local locator to the ETR that is sending the Map-Reply. When a Map-Server is doing proxy Map-Replying [LISP-MS] for a LISP site, the L bit is set to 0 for all locators in this locator-set. p: when this bit is set, an ETR informs the RLOC-probing ITR that the locator address, for which this bit is set, is the one being RLOC- probed and may be different from the source address of the Map- Reply. An ITR that RLOC-probes a particular locator, MUST use this locator for retrieving the data structure used to store the fact that the locator is reachable. The "p" bit is set for a single locator in the same locator set. If an implementation sets more than one "p" bit erroneously, the receiver of the Map-Reply MUST select the first locator. The "p" bit MUST NOT be set for locator-set records sent in Map-Request and Map-Register messages. R: set when the sender of a Map-Reply has a route to the locator in the locator data record. This receiver may find this useful to know when determining if the locator is reachable from the receiver. See also Section 6.4 for another way the R-bit may be used. Locator: an IPv4 or IPv6 address (as encoded by the 'Loc-AFI' field) assigned to an ETR. Note that the destination RLOC address MAY be an anycast address. A source RLOC can be an anycast address as well. The source or destination RLOC MUST NOT be the broadcast address (255.255.255.255 or any subnet broadcast address known to the router), and MUST NOT be a link-local multicast address. The source RLOC MUST NOT be a multicast address. The destination RLOC SHOULD be a multicast address if it is being mapped from a multicast destination EID. Mapping Protocol Data: See [CONS] or [ALT] for details. This field is optional and present when the UDP length indicates there is enough space in the packet to include it. 6.1.5. EID-to-RLOC UDP Map-Reply Message A Map-Reply returns an EID-prefix with a prefix length that is less than or equal to the EID being requested. The EID being requested is either from the destination field of an IP header of a Data-Probe or the EID record of a Map-Request. The RLOCs in the Map-Reply are globally-routable IP addresses of all ETRs for the LISP site. Each RLOC conveys status reachability but does not convey path reachability from a requesters perspective. Separate testing of path reachability is required, See Section 6.3 for details. Farinacci, et al. Expires April 14, 2011 [Page 35] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 Note that a Map-Reply may contain different EID-prefix granularity (prefix + length) than the Map-Request which triggers it. This might occur if a Map-Request were for a prefix that had been returned by an earlier Map-Reply. In such a case, the requester updates its cache with the new prefix information and granularity. For example, a requester with two cached EID-prefixes that are covered by a Map- Reply containing one, less-specific prefix, replaces the entry with the less-specific EID-prefix. Note that the reverse, replacement of one less-specific prefix with multiple more-specific prefixes, can also occur but not by removing the less-specific prefix rather by adding the more-specific prefixes which during a lookup will override the less-specific prefix. When an ETR is configured with overlapping EID-prefixes, a Map- Request with an EID that longest matches any EID-prefix MUST be returned in a single Map-Reply message. For instance, if an ETR had database mapping entries for EID-prefixes: 10.0.0.0/8 10.1.0.0/16 10.1.1.0/24 10.1.2.0/24 A Map-Request for EID 10.1.1.1 would cause a Map-Reply with a record count of 1 to be returned with a mapping record EID-prefix of 10.1.1.0/24. A Map-Request for EID 10.1.5.5, would cause a Map-Reply with a record count of 3 to be returned with mapping records for EID-prefixes 10.1.0.0/16, 10.1.1.0/24, and 10.1.2.0/24. Note that not all overlapping EID-prefixes need to be returned, only the more specifics (note in the second example above 10.0.0.0/8 was not returned for requesting EID 10.1.5.5) entries for the matching EID-prefix of the requesting EID. When more than one EID-prefix is returned, all SHOULD use the same Time-to-Live value so they can all time out at the same time. When a more specific EID-prefix is received later, its Time-to-Live value in the Map-Reply record can be stored even when other less specifics exist. When a less specific EID-prefix is received later, its map-cache expiration time SHOULD be set to the minimum expiration time of any more specific EID-prefix in the map-cache. Map-Replies SHOULD be sent for an EID-prefix no more often than once per second to the same requesting router. For scalability, it is expected that aggregation of EID addresses into EID-prefixes will allow one Map-Reply to satisfy a mapping for the EID addresses in the prefix range thereby reducing the number of Map-Request messages. Farinacci, et al. Expires April 14, 2011 [Page 36] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 Map-Reply records can have an empty locator-set. A negative Map- Reply is a Map-Reply with an empty locator-set. Negative Map-Replies convey special actions by the sender to the ITR or PTR which have solicited the Map-Reply. There are two primary applications for Negative Map-Replies. The first is for a Map-Resolver to instruct an ITR or PTR when a destination is for a LISP site versus a non-LISP site. And the other is to source quench Map-Requests which are sent for non-allocated EIDs. For each Map-Reply record, the list of locators in a locator-set MUST appear in the same order for each ETR that originates a Map-Reply message. The locator-set MUST be sorted in order of ascending IP address where an IPv4 locator address is considered numerically 'less than' an IPv6 locator address. When sending a Map-Reply message, the destination address is copied from the one of the ITR-RLOC fields from the Map-Request. The ETR can choose a locator address from one of the address families it supports. For Data-Probes, the destination address of the Map-Reply is copied from the source address of the Data-Probe message which is invoking the reply. The source address of the Map-Reply is one of the local locator addresses listed in the locator-set of any mapping record in the message and SHOULD be chosen to allow uRPF checks to succeed in the upstream service provider. The destination port of a Map-Reply message is copied from the source port of the Map-Request or Data-Probe and the source port of the Map-Reply message is set to the well-known UDP port 4342. 6.1.5.1. Traffic Redirection with Coarse EID-Prefixes When an ETR is misconfigured or compromised, it could return coarse EID-prefixes in Map-Reply messages it sends. The EID-prefix could cover EID-prefixes which are allocated to other sites redirecting their traffic to the locators of the compromised site. To solve this problem, there are two basic solutions that could be used. The first is to have Map-Servers proxy-map-reply on behalf of ETRs so their registered EID-prefixes are the ones returned in Map- Replies. Since the interaction between an ETR and Map-Server is secured with shared-keys, it is more difficult for an ETR to misbehave. The second solution is to have ITRs and PTRs cache EID- prefixes with mask-lengths that are greater than or equal to a configured prefix length. This limits the damage to a specific width of any EID-prefix advertised, but needs to be coordinated with the allocation of site prefixes. These solutions can be used independently or at the same time. At the time of this writing, other approaches are being considered Farinacci, et al. Expires April 14, 2011 [Page 37] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 and researched. 6.1.6. Map-Register Message Format The usage details of the Map-Register message can be found in specification [LISP-MS]. This section solely defines the message format. The message is sent in UDP with a destination UDP port of 4342 and a randomly selected UDP source port number. The Map-Register message format is: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Type=3 |P| Reserved | Record Count | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Nonce . . . | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | . . . Nonce | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Key ID | Authentication Data Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ Authentication Data ~ +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | Record TTL | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ R | Locator Count | EID mask-len | ACT |A| Reserved | e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ c | Rsvd | Map-Version Number | EID-AFI | o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ r | EID-prefix | d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | /| Priority | Weight | M Priority | M Weight | | L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | o | Unused Flags |L|p|R| Loc-AFI | | c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | \| Locator | +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Packet field descriptions: Farinacci, et al. Expires April 14, 2011 [Page 38] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 Type: 3 (Map-Register) P: This is the proxy-map-reply bit, when set to 1 an ETR sends a Map- Register message requesting for the Map-Server to proxy Map-Reply. The Map-Server will send non-authoritative Map-Replies on behalf of the ETR. Details on this usage will be provided in a future version of this draft. Reserved: Set to 0 on transmission and ignored on receipt. Record Count: The number of records in this Map-Register message. A record is comprised of that portion of the packet labeled 'Record' above and occurs the number of times equal to Record count. Nonce: This 8-byte Nonce field is set to 0 in Map-Register messages. Key ID: A configured ID to find the configured Message Authentication Code (MAC) algorithm and key value used for the authentication function. Authentication Data Length: The length in bytes of the Authentication Data field that follows this field. The length of the Authentication Data field is dependent on the Message Authentication Code (MAC) algorithm used. The length field allows a device that doesn't know the MAC algorithm to correctly parse the packet. Authentication Data: The message digest used from the output of the Message Authentication Code (MAC) algorithm. The entire Map- Register payload is authenticated with this field preset to 0. After the MAC is computed, it is placed in this field. Implementations of this specification MUST include support for HMAC-SHA-1-96 [RFC2404] and support for HMAC-SHA-128-256 [RFC4634] is recommended. The definition of the rest of the Map-Register can be found in the Map-Reply section. 6.1.7. Encapsulated Control Message Format An Encapsulated Control Message is used to encapsulate control packets sent between xTRs and the mapping database system described in [LISP-MS]. Farinacci, et al. Expires April 14, 2011 [Page 39] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / | IPv4 or IPv6 Header | OH | (uses RLOC addresses) | \ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / | Source Port = xxxx | Dest Port = 4342 | UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \ | UDP Length | UDP Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ LH |Type=8 | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / | IPv4 or IPv6 Header | IH | (uses RLOC or EID addresses) | \ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / | Source Port = xxxx | Dest Port = yyyy | UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \ | UDP Length | UDP Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ LCM | LISP Control Message | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Packet header descriptions: OH: The outer IPv4 or IPv6 header which uses RLOC addresses in the source and destination header address fields. UDP: The outer UDP header with destination port 4342. The source port is randomly allocated. The checksum field MUST be non-zero. LH: Type 8 is defined to be a "LISP Encapsulated Control Message" and what follows is either an IPv4 or IPv6 header as encoded by the first 4 bits after the reserved field. IH: The inner IPv4 or IPv6 header which can use either RLOC or EID addresses in the header address fields. When a Map-Request is encapsulated in this packet format the destination address in this header is an EID. UDP: The inner UDP header where the port assignments depends on the control packet being encapsulated. When the control packet is a Map-Request or Map-Register, the source port is ITR/PITR selected and the destination port is 4342. When the control packet is a Map-Reply, the source port is 4342 and the destination port is assigned from the source port of the invoking Map-Request. Port number 4341 MUST NOT be assigned to either port. The checksum Farinacci, et al. Expires April 14, 2011 [Page 40] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 field MUST be non-zero. LCM: The format is one of the control message formats described in this section. At this time, only Map-Request messages and PIM Join-Prune messages [MLISP] are allowed to be encapsulated. Encapsulating other types of LISP control messages are for further study. When Map-Requests are sent for RLOC-probing purposes (i.e the probe-bit is set), they MUST NOT be sent inside Encapsulated Control Messages. 6.2. Routing Locator Selection Both client-side and server-side may need control over the selection of RLOCs for conversations between them. This control is achieved by manipulating the Priority and Weight fields in EID-to-RLOC Map-Reply messages. Alternatively, RLOC information may be gleaned from received tunneled packets or EID-to-RLOC Map-Request messages. The following enumerates different scenarios for choosing RLOCs and the controls that are available: o Server-side returns one RLOC. Client-side can only use one RLOC. Server-side has complete control of the selection. o Server-side returns a list of RLOC where a subset of the list has the same best priority. Client can only use the subset list according to the weighting assigned by the server-side. In this case, the server-side controls both the subset list and load- splitting across its members. The client-side can use RLOCs outside of the subset list if it determines that the subset list is unreachable (unless RLOCs are set to a Priority of 255). Some sharing of control exists: the server-side determines the destination RLOC list and load distribution while the client-side has the option of using alternatives to this list if RLOCs in the list are unreachable. o Server-side sets weight of 0 for the RLOC subset list. In this case, the client-side can choose how the traffic load is spread across the subset list. Control is shared by the server-side determining the list and the client determining load distribution. Again, the client can use alternative RLOCs if the server-provided list of RLOCs are unreachable. o Either side (more likely on the server-side ETR) decides not to send a Map-Request. For example, if the server-side ETR does not send Map-Requests, it gleans RLOCs from the client-side ITR, giving the client-side ITR responsibility for bidirectional RLOC reachability and preferability. Server-side ETR gleaning of the Farinacci, et al. Expires April 14, 2011 [Page 41] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 client-side ITR RLOC is done by caching the inner header source EID and the outer header source RLOC of received packets. The client-side ITR controls how traffic is returned and can alternate using an outer header source RLOC, which then can be added to the list the server-side ETR uses to return traffic. Since no Priority or Weights are provided using this method, the server- side ETR MUST assume each client-side ITR RLOC uses the same best Priority with a Weight of zero. In addition, since EID-prefix encoding cannot be conveyed in data packets, the EID-to-RLOC cache on tunnel routers can grow to be very large. o A "gleaned" map-cache entry, one learned from the source RLOC of a received encapsulated packet, is only stored and used for a few seconds, pending verification. Verification is performed by sending a Map-Request to the source EID (the inner header IP source address) of the received encapsulated packet. A reply to this "verifying Map-Request" is used to fully populate the map- cache entry for the "gleaned" EID and is stored and used for the time indicated from the TTL field of a received Map-Reply. When a verified map-cache entry is stored, data gleaning no longer occurs for subsequent packets which have a source EID that matches the EID-prefix of the verified entry. RLOCs that appear in EID-to-RLOC Map-Reply messages are assumed to be reachable when the R-bit for the locator record is set to 1. Neither the information contained in a Map-Reply or that stored in the mapping database system provides reachability information for RLOCs. Note that reachability is not part of the mapping system and is determined using one or more of the Routing Locator Reachability Algorithms described in the next section. 6.3. Routing Locator Reachability Several mechanisms for determining RLOC reachability are currently defined: 1. An ETR may examine the Loc-Status-Bits in the LISP header of an encapsulated data packet received from an ITR. If the ETR is also acting as an ITR and has traffic to return to the original ITR site, it can use this status information to help select an RLOC. 2. An ITR may receive an ICMP Network or ICMP Host Unreachable message for an RLOC it is using. This indicates that the RLOC is likely down. 3. An ITR which participates in the global routing system can determine that an RLOC is down if no BGP RIB route exists that Farinacci, et al. Expires April 14, 2011 [Page 42] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 matches the RLOC IP address. 4. An ITR may receive an ICMP Port Unreachable message from a destination host. This occurs if an ITR attempts to use interworking [INTERWORK] and LISP-encapsulated data is sent to a non-LISP-capable site. 5. An ITR may receive a Map-Reply from a ETR in response to a previously sent Map-Request. The RLOC source of the Map-Reply is likely up since the ETR was able to send the Map-Reply to the ITR. 6. When an ETR receives an encapsulated packet from an ITR, the source RLOC from the outer header of the packet is likely up. 7. An ITR/ETR pair can use the Locator Reachability Algorithms described in this section, namely Echo-Noncing or RLOC-Probing. When determining Locator up/down reachability by examining the Loc- Status-Bits from the LISP encapsulated data packet, an ETR will receive up to date status from an encapsulating ITR about reachability for all ETRs at the site. CE-based ITRs at the source site can determine reachability relative to each other using the site IGP as follows: o Under normal circumstances, each ITR will advertise a default route into the site IGP. o If an ITR fails or if the upstream link to its PE fails, its default route will either time-out or be withdrawn. Each ITR can thus observe the presence or lack of a default route originated by the others to determine the Locator Status Bits it sets for them. RLOCs listed in a Map-Reply are numbered with ordinals 0 to n-1. The Loc-Status-Bits in a LISP encapsulated packet are numbered from 0 to n-1 starting with the least significant bit. For example, if an RLOC listed in the 3rd position of the Map-Reply goes down (ordinal value 2), then all ITRs at the site will clear the 3rd least significant bit (xxxx x0xx) of the Loc-Status-Bits field for the packets they encapsulate. When an ETR decapsulates a packet, it will check for any change in the Loc-Status-Bits field. When a bit goes from 1 to 0, the ETR will refrain from encapsulating packets to an RLOC that is indicated as down. It will only resume using that RLOC if the corresponding Loc- Status-Bit returns to a value of 1. Loc-Status-Bits are associated Farinacci, et al. Expires April 14, 2011 [Page 43] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 with a locator-set per EID-prefix. Therefore, when a locator becomes unreachable, the Loc-Status-Bit that corresponds to that locator's position in the list returned by the last Map-Reply will be set to zero for that particular EID-prefix. When ITRs at the site are not deployed in CE routers, the IGP can still be used to determine the reachability of Locators provided they are injected into the IGP. This is typically done when a /32 address is configured on a loopback interface. When ITRs receive ICMP Network or Host Unreachable messages as a method to determine unreachability, they will refrain from using Locators which are described in Locator lists of Map-Replies. However, using this approach is unreliable because many network operators turn off generation of ICMP Unreachable messages. If an ITR does receive an ICMP Network or Host Unreachable message, it MAY originate its own ICMP Unreachable message destined for the host that originated the data packet the ITR encapsulated. Also, BGP-enabled ITRs can unilaterally examine the BGP RIB to see if a locator address from a locator-set in a mapping entry matches a prefix. If it does not find one and BGP is running in the Default Free Zone (DFZ), it can decide to not use the locator even though the Loc-Status-Bits indicate the locator is up. In this case, the path from the ITR to the ETR that is assigned the locator is not available. More details are in [LOC-ID-ARCH]. Optionally, an ITR can send a Map-Request to a Locator and if a Map- Reply is returned, reachability of the Locator has been determined. Obviously, sending such probes increases the number of control messages originated by tunnel routers for active flows, so Locators are assumed to be reachable when they are advertised. This assumption does create a dependency: Locator unreachability is detected by the receipt of ICMP Host Unreachable messages. When an Locator has been determined to be unreachable, it is not used for active traffic; this is the same as if it were listed in a Map-Reply with priority 255. The ITR can test the reachability of the unreachable Locator by sending periodic Requests. Both Requests and Replies MUST be rate- limited. Locator reachability testing is never done with data packets since that increases the risk of packet loss for end-to-end sessions. When an ETR decapsulates a packet, it knows that it is reachable from the encapsulating ITR because that is how the packet arrived. In Farinacci, et al. Expires April 14, 2011 [Page 44] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 most cases, the ETR can also reach the ITR but cannot assume this to be true due to the possibility of path asymmetry. In the presence of unidirectional traffic flow from an ITR to an ETR, the ITR SHOULD NOT use the lack of return traffic as an indication that the ETR is unreachable. Instead, it MUST use an alternate mechanisms to determine reachability. 6.3.1. Echo Nonce Algorithm When data flows bidirectionally between locators from different sites, a simple mechanism called "nonce echoing" can be used to determine reachability between an ITR and ETR. When an ITR wants to solicit a nonce echo, it sets the N and E bits and places a 24-bit nonce in the LISP header of the next encapsulated data packet. When this packet is received by the ETR, the encapsulated packet is forwarded as normal. When the ETR next sends a data packet to the ITR, it includes the nonce received earlier with the N bit set and E bit cleared. The ITR sees this "echoed nonce" and knows the path to and from the ETR is up. The ITR will set the E-bit and N-bit for every packet it sends while in echo-nonce-request state. The time the ITR waits to process the echoed nonce before it determines the path is unreachable is variable and a choice left for the implementation. If the ITR is receiving packets from the ETR but does not see the nonce echoed while being in echo-nonce-request state, then the path to the ETR is unreachable. This decision may be overridden by other locator reachability algorithms. Once the ITR determines the path to the ETR is down it can switch to another locator for that EID-prefix. Note that "ITR" and "ETR" are relative terms here. Both devices MUST be implementing both ITR and ETR functionality for the echo nonce mechanism to operate. The ITR and ETR may both go into echo-nonce-request state at the same time. The number of packets sent or the time during which echo nonce requests are sent is an implementation specific setting. However, when an ITR is in echo-nonce-request state, it can echo the ETR's nonce in the next set of packets that it encapsulates and then subsequently, continue sending echo-nonce-request packets. This mechanism does not completely solve the forward path reachability problem as traffic may be unidirectional. That is, the ETR receiving traffic at a site may not be the same device as an ITR which transmits traffic from that site or the site to site traffic is unidirectional so there is no ITR returning traffic. Farinacci, et al. Expires April 14, 2011 [Page 45] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 The echo-nonce algorithm is bilateral. That is, if one side sets the E-bit and the other side is not enabled for echo-noncing, then the echoing of the nonce does not occur and the requesting side may regard the locator unreachable erroneously. An ITR SHOULD only set the E-bit in a encapsulated data packet when it knows the ETR is enabled for echo-noncing. This is conveyed by the E-bit in the Map- Reply message. Note that other locator reachability mechanisms are being researched and can be used to compliment or even override the Echo Nonce Algorithm. See next section for an example of control-plane probing. 6.3.2. RLOC Probing Algorithm RLOC Probing is a method that an ITR or PTR can use to determine the reachability status of one or more locators that it has cached in a map-cache entry. The probe-bit of the Map-Request and Map-Reply messages are used for RLOC Probing. RLOC probing is done in the control-plane on a timer basis where an ITR or PTR will originate a Map-Request destined to a locator address from one of its own locator addresses. A Map-Request used as an RLOC-probe is NOT encapsulated and NOT sent to a Map-Server or on the ALT like one would when soliciting mapping data. The EID record encoded in the Map-Request is the EID-prefix of the map-cache entry cached by the ITR or PTR. The ITR may include a mapping data record for its own database mapping information which contains the local EID-prefixes and RLOCs for its site. When an ETR receives a Map-Request message with the probe-bit set, it returns a Map-Reply with the probe-bit set. The source address of the Map-Reply is set from the destination address of the Map-Request and the destination address of the Map-Reply is set from the source address of the Map-Request. The Map-Reply SHOULD contain mapping data for the EID-prefix contained in the Map-Request. This provides the opportunity for the ITR or PTR, which sent the RLOC-probe to get mapping updates if there were changes to the ETR's database mapping entries. There are advantages and disadvantages of RLOC Probing. The greatest benefit of RLOC Probing is that it can handle many failure scenarios allowing the ITR to determine when the path to a specific locator is reachable or has become unreachable, thus providing a robust mechanism for switching to using another locator from the cached locator. RLOC Probing can also provide rough RTT estimates between a pair of locators which can be useful for network management purposes as well as for selecting low delay paths. The major disadvantage of RLOC Probing is in the number of control messages required and the Farinacci, et al. Expires April 14, 2011 [Page 46] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 amount of bandwidth used to obtain those benefits, especially if the requirement for failure detection times are very small. Continued research and testing will attempt to characterize the tradeoffs of failure detection times versus message overhead. 6.4. EID Reachability within a LISP Site A site may be multihomed using two or more ETRs. The hosts and infrastructure within a site will be addressed using one or more EID prefixes that are mapped to the RLOCs of the relevant ETRs in the mapping system. One possible failure mode is for an ETR to lose reachability to one or more of the EID prefixes within its own site. When this occurs when the ETR sends Map-Replies, it can clear the R-bit associated with its own locator. And when the ETR is also an ITR, it can clear its locator-status-bit in the encapsulation data header. 6.5. Routing Locator Hashing When an ETR provides an EID-to-RLOC mapping in a Map-Reply message to a requesting ITR, the locator-set for the EID-prefix may contain different priority values for each locator address. When more than one best priority locator exists, the ITR can decide how to load share traffic against the corresponding locators. The following hash algorithm may be used by an ITR to select a locator for a packet destined to an EID for the EID-to-RLOC mapping: 1. Either a source and destination address hash can be used or the traditional 5-tuple hash which includes the source and destination addresses, source and destination TCP, UDP, or SCTP port numbers and the IP protocol number field or IPv6 next- protocol fields of a packet a host originates from within a LISP site. When a packet is not a TCP, UDP, or SCTP packet, the source and destination addresses only from the header are used to compute the hash. 2. Take the hash value and divide it by the number of locators stored in the locator-set for the EID-to-RLOC mapping. 3. The remainder will be yield a value of 0 to "number of locators minus 1". Use the remainder to select the locator in the locator-set. Note that when a packet is LISP encapsulated, the source port number in the outer UDP header needs to be set. Selecting a hashed value allows core routers which are attached to Link Aggregation Groups Farinacci, et al. Expires April 14, 2011 [Page 47] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 (LAGs) to load-split the encapsulated packets across member links of such LAGs. Otherwise, core routers would see a single flow, since packets have a source address of the ITR, for packets which are originated by different EIDs at the source site. A suggested setting for the source port number computed by an ITR is a 5-tuple hash function on the inner header, as described above. Many core router implementations use a 5-tuple hash to decide how to balance packet load across members of a LAG. The 5-tuple hash includes the source and destination addresses of the packet and the source and destination ports when the protocol number in the packet is TCP or UDP. For this reason, UDP encoding is used for LISP encapsulation. 6.6. Changing the Contents of EID-to-RLOC Mappings Since the LISP architecture uses a caching scheme to retrieve and store EID-to-RLOC mappings, the only way an ITR can get a more up-to- date mapping is to re-request the mapping. However, the ITRs do not know when the mappings change and the ETRs do not keep track of which ITRs requested its mappings. For scalability reasons, we want to maintain this approach but need to provide a way for ETRs change their mappings and inform the sites that are currently communicating with the ETR site using such mappings. When a locator record is added to the end of a locator-set, it is easy to update mappings. We assume new mappings will maintain the same locator ordering as the old mapping but just have new locators appended to the end of the list. So some ITRs can have a new mapping while other ITRs have only an old mapping that is used until they time out. When an ITR has only an old mapping but detects bits set in the loc-status-bits that correspond to locators beyond the list it has cached, it simply ignores them. However, this can only happen for locator addresses that are lexicographically greater than the locator addresses in the existing locator-set. When a locator record is removed from a locator-set, ITRs that have the mapping cached will not use the removed locator because the xTRs will set the loc-status-bit to 0. So even if the locator is in the list, it will not be used. For new mapping requests, the xTRs can set the locator AFI to 0 (indicating an unspecified address), as well as setting the corresponding loc-status-bit to 0. This forces ITRs with old or new mappings to avoid using the removed locator. If many changes occur to a mapping over a long period of time, one will find empty record slots in the middle of the locator-set and new records appended to the locator-set. At some point, it would be useful to compact the locator-set so the loc-status-bit settings can Farinacci, et al. Expires April 14, 2011 [Page 48] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 be efficiently packed. We propose here three approaches for locator-set compaction, one operational and two protocol mechanisms. The operational approach uses a clock sweep method. The protocol approaches use the concept of Solicit-Map-Requests and Map-Versioning. 6.6.1. Clock Sweep The clock sweep approach uses planning in advance and the use of count-down TTLs to time out mappings that have already been cached. The default setting for an EID-to-RLOC mapping TTL is 24 hours. So there is a 24 hour window to time out old mappings. The following clock sweep procedure is used: 1. 24 hours before a mapping change is to take effect, a network administrator configures the ETRs at a site to start the clock sweep window. 2. During the clock sweep window, ETRs continue to send Map-Reply messages with the current (unchanged) mapping records. The TTL for these mappings is set to 1 hour. 3. 24 hours later, all previous cache entries will have timed out, and any active cache entries will time out within 1 hour. During this 1 hour window the ETRs continue to send Map-Reply messages with the current (unchanged) mapping records with the TTL set to 1 minute. 4. At the end of the 1 hour window, the ETRs will send Map-Reply messages with the new (changed) mapping records. So any active caches can get the new mapping contents right away if not cached, or in 1 minute if they had the mapping cached. The new mappings are cached with a time to live equal to the TTL in the Map-Reply. 6.6.2. Solicit-Map-Request (SMR) Soliciting a Map-Request is a selective way for ETRs, at the site where mappings change, to control the rate they receive requests for Map-Reply messages. SMRs are also used to tell remote ITRs to update the mappings they have cached. Since the ETRs don't keep track of remote ITRs that have cached their mappings, they do not know which ITRs need to have their mappings updated. As a result, an ETR will solicit Map-Requests (called an SMR message) from those sites to which it has been sending encapsulated data to for the last minute. In particular, an ETR will send an SMR an ITR to which it has recently sent encapsulated data. Farinacci, et al. Expires April 14, 2011 [Page 49] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 An SMR message is simply a bit set in a Map-Request message. An ITR or PTR will send a Map-Request when they receive an SMR message. Both the SMR sender and the Map-Request responder MUST rate-limited these messages. Rate-limiting can be implemented as a global rate- limiter or one rate-limiter per SMR destination. The following procedure shows how a SMR exchange occurs when a site is doing locator-set compaction for an EID-to-RLOC mapping: 1. When the database mappings in an ETR change, the ETRs at the site begin to send Map-Requests with the SMR bit set for each locator in each map-cache entry the ETR caches. 2. A remote ITR which receives the SMR message will schedule sending a Map-Request message to the source locator address of the SMR message or to the mapping database system. A newly allocated random nonce is selected and the EID-prefix used is the one copied from the SMR message. If the source locator is the only locator in the cached locator-set, the remote ITR SHOULD send a Map-Request to the database mapping system just in case the single locator has changed and may no longer be reachable to accept the Map-Request. 3. The remote ITR MUST rate-limit the Map-Request until it gets a Map-Reply while continuing to use the cached mapping. When Map Versioning is used, described in Section 6.6.3, an SMR sender can detect if an ITR is using the most up to date database mapping. 4. The ETRs at the site with the changed mapping will reply to the Map-Request with a Map-Reply message that has a nonce from the SMR-invoked Map-Request. The Map-Reply messages SHOULD be rate limited. This is important to avoid Map-Reply implosion. 5. The ETRs, at the site with the changed mapping, record the fact that the site that sent the Map-Request has received the new mapping data in the mapping cache entry for the remote site so the loc-status-bits are reflective of the new mapping for packets going to the remote site. The ETR then stops sending SMR messages. For security reasons an ITR MUST NOT process unsolicited Map-Replies. To avoid map-cache entry corruption by a third-party, a sender of an SMR-based Map-Request MUST be verified. If an ITR receives an SMR- based Map-Request and the source is not in the locator-set for the stored map-cache entry, then the responding Map-Request MUST be sent with an EID destination to the mapping database system. Since the mapping database system is more secure to reach an authoritative ETR, it will deliver the Map-Request to the authoritative source of the Farinacci, et al. Expires April 14, 2011 [Page 50] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 mapping data. When an ITR receives an SMR-based Map-Request for which it does not have a cached mapping for the EID in the SMR message, it MAY not send a SMR-invoked Map-Request. This scenario can occur when an ETR sends SMR messages to all locators in the locator-set it has stored in its map-cache but the remote ITRs that receive the SMR may not be sending packets to the site. There is no point in updating the ITRs until they need to send, in which case, they will send Map-Requests to obtain a map-cache entry. 6.6.3. Database Map Versioning When there is unidirectional packet flow between an ITR and ETR, and the EID-to-RLOC mappings change on the ETR, it needs to inform the ITR so encapsulation can stop to a removed locator and start to a new locator in the locator-set. An ETR, when it sends Map-Reply messages, conveys its own Map-Version number. This is known as the Destination Map-Version Number. ITRs include the Destination Map-Version Number in packets they encapsulate to the site. When an ETR decapsulates a packet and detects the Destination Map-Version Number is less than the current version for its mapping, the SMR procedure described in Section 6.6.2 occurs. An ITR, when it encapsulates packets to ETRs, can convey its own Map- Version number. This is known as the Source Map-Version Number. When an ETR decapsulates a packet and detects the Source Map-Version Number is greater than the last Map-Version Number sent in a Map- Reply from the ITR's site, the ETR will send a Map-Request to one of the ETRs for the source site. A Map-Version Number is used as a sequence number per EID-prefix. So values that are greater, are considered to be more recent. A value of 0 for the Source Map-Version Number or the Destination Map-Version Number conveys no versioning information and an ITR does no comparison with previously received Map-Version Numbers. A Map-Version Number can be included in Map-Register messages as well. This is a good way for the Map-Server can assure that all ETRs for a site registering to it will be Map-Version number synchronized. See [VERSIONING] for a more detailed analysis and description of Database Map Versioning. Farinacci, et al. Expires April 14, 2011 [Page 51] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 7. Router Performance Considerations LISP is designed to be very hardware-based forwarding friendly. A few implementation techniques can be used to incrementally implement LISP: o When a tunnel encapsulated packet is received by an ETR, the outer destination address may not be the address of the router. This makes it challenging for the control plane to get packets from the hardware. This may be mitigated by creating special FIB entries for the EID-prefixes of EIDs served by the ETR (those for which the router provides an RLOC translation). These FIB entries are marked with a flag indicating that control plane processing should be performed. The forwarding logic of testing for particular IP protocol number value is not necessary. No changes to existing, deployed hardware should be needed to support this. o On an ITR, prepending a new IP header consists of adding more bytes to a MAC rewrite string and prepending the string as part of the outgoing encapsulation procedure. Routers that support GRE tunneling [RFC2784] or 6to4 tunneling [RFC3056] may already support this action. o A packet's source address or interface the packet was received on can be used to select a VRF (Virtual Routing/Forwarding). The VRF's routing table can be used to find EID-to-RLOC mappings. Farinacci, et al. Expires April 14, 2011 [Page 52] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 8. Deployment Scenarios This section will explore how and where ITRs and ETRs can be deployed and will discuss the pros and cons of each deployment scenario. There are two basic deployment trade-offs to consider: centralized versus distributed caches and flat, recursive, or re-encapsulating tunneling. When deciding on centralized versus distributed caching, the following issues should be considered: o Are the tunnel routers spread out so that the caches are spread across all the memories of each router? o Should management "touch points" be minimized by choosing few tunnel routers, just enough for redundancy? o In general, using more ITRs doesn't increase management load, since caches are built and stored dynamically. On the other hand, more ETRs does require more management since EID-prefix-to-RLOC mappings need to be explicitly configured. When deciding on flat, recursive, or re-encapsulation tunneling, the following issues should be considered: o Flat tunneling implements a single tunnel between source site and destination site. This generally offers better paths between sources and destinations with a single tunnel path. o Recursive tunneling is when tunneled traffic is again further encapsulated in another tunnel, either to implement VPNs or to perform Traffic Engineering. When doing VPN-based tunneling, the site has some control since the site is prepending a new tunnel header. In the case of TE-based tunneling, the site may have control if it is prepending a new tunnel header, but if the site's ISP is doing the TE, then the site has no control. Recursive tunneling generally will result in suboptimal paths but at the benefit of steering traffic to resource available parts of the network. o The technique of re-encapsulation ensures that packets only require one tunnel header. So if a packet needs to be rerouted, it is first decapsulated by the ETR and then re-encapsulated with a new tunnel header using a new RLOC. The next sub-sections will survey where tunnel routers can reside in the network. Farinacci, et al. Expires April 14, 2011 [Page 53] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 8.1. First-hop/Last-hop Tunnel Routers By locating tunnel routers close to hosts, the EID-prefix set is at the granularity of an IP subnet. So at the expense of more EID- prefix-to-RLOC sets for the site, the caches in each tunnel router can remain relatively small. But caches always depend on the number of non-aggregated EID destination flows active through these tunnel routers. With more tunnel routers doing encapsulation, the increase in control traffic grows as well: since the EID-granularity is greater, more Map-Requests and Map-Replies are traveling between more routers. The advantage of placing the caches and databases at these stub routers is that the products deployed in this part of the network have better price-memory ratios then their core router counterparts. Memory is typically less expensive in these devices and fewer routes are stored (only IGP routes). These devices tend to have excess capacity, both for forwarding and routing state. LISP functionality can also be deployed in edge switches. These devices generally have layer-2 ports facing hosts and layer-3 ports facing the Internet. Spare capacity is also often available in these devices as well. 8.2. Border/Edge Tunnel Routers Using customer-edge (CE) routers for tunnel endpoints allows the EID space associated with a site to be reachable via a small set of RLOCs assigned to the CE routers for that site. This is the default behavior envisioned in the rest of this specification. This offers the opposite benefit of the first-hop/last-hop tunnel router scenario: the number of mapping entries and network management touch points are reduced, allowing better scaling. One disadvantage is that less of the network's resources are used to reach host endpoints thereby centralizing the point-of-failure domain and creating network choke points at the CE router. Note that more than one CE router at a site can be configured with the same IP address. In this case an RLOC is an anycast address. This allows resilience between the CE routers. That is, if a CE router fails, traffic is automatically routed to the other routers using the same anycast address. However, this comes with the disadvantage where the site cannot control the entrance point when the anycast route is advertised out from all border routers. Another disadvantage of using anycast locators is the limited advertisement Farinacci, et al. Expires April 14, 2011 [Page 54] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 scope of /32 (or /128 for IPv6) routes. 8.3. ISP Provider-Edge (PE) Tunnel Routers Use of ISP PE routers as tunnel endpoint routers is not the typical deployment scenario envisioned in the specification. This section attempts to capture some of reasoning behind this preference of implementing LISP on CE routers. Use of ISP PE routers as tunnel endpoint routers gives an ISP, rather than a site, control over the location of the egress tunnel endpoints. That is, the ISP can decide if the tunnel endpoints are in the destination site (in either CE routers or last-hop routers within a site) or at other PE edges. The advantage of this case is that two tunnel headers can be avoided. By having the PE be the first router on the path to encapsulate, it can choose a TE path first, and the ETR can decapsulate and re-encapsulate for a tunnel to the destination end site. An obvious disadvantage is that the end site has no control over where its packets flow or the RLOCs used. Other disadvantages include the difficulty in synchronizing path liveness updates between CE and PE routers. As mentioned in earlier sections a combination of these scenarios is possible at the expense of extra packet header overhead, if both site and provider want control, then recursive or re-encapsulating tunnels are used. 8.4. LISP Functionality with Conventional NATs LISP routers can be deployed behind Network Address Translator (NAT) devices to provide the same set of packet services hosts have today when they are addressed out of private address space. It is important to note that a locator address in any LISP control message MUST be a globally routable address and therefore SHOULD NOT contain [RFC1918] addresses. If a LISP router is configured with private addresses, they MUST be used only in the outer IP header so the NAT device can translate properly. Otherwise, EID addresses MUST be translated before encapsulation is performed. Both NAT translation and LISP encapsulation functions could be co-located in the same device. More details on LISP address translation can be found in [INTERWORK]. Farinacci, et al. Expires April 14, 2011 [Page 55] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 9. Traceroute Considerations When a source host in a LISP site initiates a traceroute to a destination host in another LISP site, it is highly desirable for it to see the entire path. Since packets are encapsulated from ITR to ETR, the hop across the tunnel could be viewed as a single hop. However, LISP traceroute will provide the entire path so the user can see 3 distinct segments of the path from a source LISP host to a destination LISP host: Segment 1 (in source LISP site based on EIDs): source-host ---> first-hop ... next-hop ---> ITR Segment 2 (in the core network based on RLOCs): ITR ---> next-hop ... next-hop ---> ETR Segment 3 (in the destination LISP site based on EIDs): ETR ---> next-hop ... last-hop ---> destination-host For segment 1 of the path, ICMP Time Exceeded messages are returned in the normal matter as they are today. The ITR performs a TTL decrement and test for 0 before encapsulating. So the ITR hop is seen by the traceroute source has an EID address (the address of site-facing interface). For segment 2 of the path, ICMP Time Exceeded messages are returned to the ITR because the TTL decrement to 0 is done on the outer header, so the destination of the ICMP messages are to the ITR RLOC address, the source RLOC address of the encapsulated traceroute packet. The ITR looks inside of the ICMP payload to inspect the traceroute source so it can return the ICMP message to the address of the traceroute client as well as retaining the core router IP address in the ICMP message. This is so the traceroute client can display the core router address (the RLOC address) in the traceroute output. The ETR returns its RLOC address and responds to the TTL decrement to 0 like the previous core routers did. For segment 3, the next-hop router downstream from the ETR will be decrementing the TTL for the packet that was encapsulated, sent into the core, decapsulated by the ETR, and forwarded because it isn't the final destination. If the TTL is decremented to 0, any router on the path to the destination of the traceroute, including the next-hop router or destination, will send an ICMP Time Exceeded message to the source EID of the traceroute client. The ICMP message will be Farinacci, et al. Expires April 14, 2011 [Page 56] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 encapsulated by the local ITR and sent back to the ETR in the originated traceroute source site, where the packet will be delivered to the host. 9.1. IPv6 Traceroute IPv6 traceroute follows the procedure described above since the entire traceroute data packet is included in ICMP Time Exceeded message payload. Therefore, only the ITR needs to pay special attention for forwarding ICMP messages back to the traceroute source. 9.2. IPv4 Traceroute For IPv4 traceroute, we cannot follow the above procedure since IPv4 ICMP Time Exceeded messages only include the invoking IP header and 8 bytes that follow the IP header. Therefore, when a core router sends an IPv4 Time Exceeded message to an ITR, all the ITR has in the ICMP payload is the encapsulated header it prepended followed by a UDP header. The original invoking IP header, and therefore the identity of the traceroute source is lost. The solution we propose to solve this problem is to cache traceroute IPv4 headers in the ITR and to match them up with corresponding IPv4 Time Exceeded messages received from core routers and the ETR. The ITR will use a circular buffer for caching the IPv4 and UDP headers of traceroute packets. It will select a 16-bit number as a key to find them later when the IPv4 Time Exceeded messages are received. When an ITR encapsulates an IPv4 traceroute packet, it will use the 16-bit number as the UDP source port in the encapsulating header. When the ICMP Time Exceeded message is returned to the ITR, the UDP header of the encapsulating header is present in the ICMP payload thereby allowing the ITR to find the cached headers for the traceroute source. The ITR puts the cached headers in the payload and sends the ICMP Time Exceeded message to the traceroute source retaining the source address of the original ICMP Time Exceeded message (a core router or the ETR of the site of the traceroute destination). The signature of a traceroute packet comes in two forms. The first form is encoded as a UDP message where the destination port is inspected for a range of values. The second form is encoded as an ICMP message where the IP identification field is inspected for a well-known value. 9.3. Traceroute using Mixed Locators When either an IPv4 traceroute or IPv6 traceroute is originated and the ITR encapsulates it in the other address family header, you Farinacci, et al. Expires April 14, 2011 [Page 57] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 cannot get all 3 segments of the traceroute. Segment 2 of the traceroute can not be conveyed to the traceroute source since it is expecting addresses from intermediate hops in the same address format for the type of traceroute it originated. Therefore, in this case, segment 2 will make the tunnel look like one hop. All the ITR has to do to make this work is to not copy the inner TTL to the outer, encapsulating header's TTL when a traceroute packet is encapsulated using an RLOC from a different address family. This will cause no TTL decrement to 0 to occur in core routers between the ITR and ETR. Farinacci, et al. Expires April 14, 2011 [Page 58] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 10. Mobility Considerations There are several kinds of mobility of which only some might be of concern to LISP. Essentially they are as follows. 10.1. Site Mobility A site wishes to change its attachment points to the Internet, and its LISP Tunnel Routers will have new RLOCs when it changes upstream providers. Changes in EID-RLOC mappings for sites are expected to be handled by configuration, outside of the LISP protocol. 10.2. Slow Endpoint Mobility An individual endpoint wishes to move, but is not concerned about maintaining session continuity. Renumbering is involved. LISP can help with the issues surrounding renumbering [RFC4192] [LISA96] by decoupling the address space used by a site from the address spaces used by its ISPs. [RFC4984] 10.3. Fast Endpoint Mobility Fast endpoint mobility occurs when an endpoint moves relatively rapidly, changing its IP layer network attachment point. Maintenance of session continuity is a goal. This is where the Mobile IPv4 [RFC3344bis] and Mobile IPv6 [RFC3775] [RFC4866] mechanisms are used, and primarily where interactions with LISP need to be explored. The problem is that as an endpoint moves, it may require changes to the mapping between its EID and a set of RLOCs for its new network location. When this is added to the overhead of mobile IP binding updates, some packets might be delayed or dropped. In IPv4 mobility, when an endpoint is away from home, packets to it are encapsulated and forwarded via a home agent which resides in the home area the endpoint's address belongs to. The home agent will encapsulate and forward packets either directly to the endpoint or to a foreign agent which resides where the endpoint has moved to. Packets from the endpoint may be sent directly to the correspondent node, may be sent via the foreign agent, or may be reverse-tunneled back to the home agent for delivery to the mobile node. As the mobile node's EID or available RLOC changes, LISP EID-to-RLOC mappings are required for communication between the mobile node and the home agent, whether via foreign agent or not. As a mobile endpoint changes networks, up to three LISP mapping changes may be required: Farinacci, et al. Expires April 14, 2011 [Page 59] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 o The mobile node moves from an old location to a new visited network location and notifies its home agent that it has done so. The Mobile IPv4 control packets the mobile node sends pass through one of the new visited network's ITRs, which needs a EID-RLOC mapping for the home agent. o The home agent might not have the EID-RLOC mappings for the mobile node's "care-of" address or its foreign agent in the new visited network, in which case it will need to acquire them. o When packets are sent directly to the correspondent node, it may be that no traffic has been sent from the new visited network to the correspondent node's network, and the new visited network's ITR will need to obtain an EID-RLOC mapping for the correspondent node's site. In addition, if the IPv4 endpoint is sending packets from the new visited network using its original EID, then LISP will need to perform a route-returnability check on the new EID-RLOC mapping for that EID. In IPv6 mobility, packets can flow directly between the mobile node and the correspondent node in either direction. The mobile node uses its "care-of" address (EID). In this case, the route-returnability check would not be needed but one more LISP mapping lookup may be required instead: o As above, three mapping changes may be needed for the mobile node to communicate with its home agent and to send packets to the correspondent node. o In addition, another mapping will be needed in the correspondent node's ITR, in order for the correspondent node to send packets to the mobile node's "care-of" address (EID) at the new network location. When both endpoints are mobile the number of potential mapping lookups increases accordingly. As a mobile node moves there are not only mobility state changes in the mobile node, correspondent node, and home agent, but also state changes in the ITRs and ETRs for at least some EID-prefixes. The goal is to support rapid adaptation, with little delay or packet loss for the entire system. Also IP mobility can be modified to require fewer mapping changes. In order to increase overall system performance, there may be a need to reduce the optimization of one area in order to place fewer demands on another. Farinacci, et al. Expires April 14, 2011 [Page 60] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 In LISP, one possibility is to "glean" information. When a packet arrives, the ETR could examine the EID-RLOC mapping and use that mapping for all outgoing traffic to that EID. It can do this after performing a route-returnability check, to ensure that the new network location does have a internal route to that endpoint. However, this does not cover the case where an ITR (the node assigned the RLOC) at the mobile-node location has been compromised. Mobile IP packet exchange is designed for an environment in which all routing information is disseminated before packets can be forwarded. In order to allow the Internet to grow to support expected future use, we are moving to an environment where some information may have to be obtained after packets are in flight. Modifications to IP mobility should be considered in order to optimize the behavior of the overall system. Anything which decreases the number of new EID- RLOC mappings needed when a node moves, or maintains the validity of an EID-RLOC mapping for a longer time, is useful. 10.4. Fast Network Mobility In addition to endpoints, a network can be mobile, possibly changing xTRs. A "network" can be as small as a single router and as large as a whole site. This is different from site mobility in that it is fast and possibly short-lived, but different from endpoint mobility in that a whole prefix is changing RLOCs. However, the mechanisms are the same and there is no new overhead in LISP. A map request for any endpoint will return a binding for the entire mobile prefix. If mobile networks become a more common occurrence, it may be useful to revisit the design of the mapping service and allow for dynamic updates of the database. The issue of interactions between mobility and LISP needs to be explored further. Specific improvements to the entire system will depend on the details of mapping mechanisms. Mapping mechanisms should be evaluated on how well they support session continuity for mobile nodes. 10.5. LISP Mobile Node Mobility A mobile device can use the LISP infrastructure to achieve mobility by implementing the LISP encapsulation and decapsulation functions and acting as a simple ITR/ETR. By doing this, such a "LISP mobile node" can use topologically-independent EID IP addresses that are not advertised into and do not impose a cost on the global routing system. These EIDs are maintained at the edges of the mapping system (in LISP Map-Servers and Map-Resolvers) and are provided on demand to only the correspondents of the LISP mobile node. Farinacci, et al. Expires April 14, 2011 [Page 61] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 Refer to the LISP Mobility Architecture specification [LISP-MN] for more details. Farinacci, et al. Expires April 14, 2011 [Page 62] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 11. Multicast Considerations A multicast group address, as defined in the original Internet architecture is an identifier of a grouping of topologically independent receiver host locations. The address encoding itself does not determine the location of the receiver(s). The multicast routing protocol, and the network-based state the protocol creates, determines where the receivers are located. In the context of LISP, a multicast group address is both an EID and a Routing Locator. Therefore, no specific semantic or action needs to be taken for a destination address, as it would appear in an IP header. Therefore, a group address that appears in an inner IP header built by a source host will be used as the destination EID. The outer IP header (the destination Routing Locator address), prepended by a LISP router, will use the same group address as the destination Routing Locator. Having said that, only the source EID and source Routing Locator needs to be dealt with. Therefore, an ITR merely needs to put its own IP address in the source Routing Locator field when prepending the outer IP header. This source Routing Locator address, like any other Routing Locator address MUST be globally routable. Therefore, an EID-to-RLOC mapping does not need to be performed by an ITR when a received data packet is a multicast data packet or when processing a source-specific Join (either by IGMPv3 or PIM). But the source Routing Locator is decided by the multicast routing protocol in a receiver site. That is, an EID to Routing Locator translation is done at control-time. Another approach is to have the ITR not encapsulate a multicast packet and allow the host built packet to flow into the core even if the source address is allocated out of the EID namespace. If the RPF-Vector TLV [RFC5496] is used by PIM in the core, then core routers can RPF to the ITR (the Locator address which is injected into core routing) rather than the host source address (the EID address which is not injected into core routing). To avoid any EID-based multicast state in the network core, the first approach is chosen for LISP-Multicast. Details for LISP-Multicast and Interworking with non-LISP sites is described in specification [MLISP]. Farinacci, et al. Expires April 14, 2011 [Page 63] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 12. Security Considerations It is believed that most of the security mechanisms will be part of the mapping database service when using control plane procedures for obtaining EID-to-RLOC mappings. For data plane triggered mappings, as described in this specification, protection is provided against ETR spoofing by using Return- Routability mechanisms evidenced by the use of a 24-bit Nonce field in the LISP encapsulation header and a 64-bit Nonce field in the LISP control message. The nonce, coupled with the ITR accepting only solicited Map-Replies goes a long way toward providing decent authentication. LISP does not rely on a PKI infrastructure or a more heavy weight authentication system. These systems challenge the scalability of LISP which was a primary design goal. DoS attack prevention will depend on implementations rate-limiting Map-Requests and Map-Replies to the control plane as well as rate- limiting the number of data-triggered Map-Replies. To deal with map-cache exhaustion attempts in an ITR/PTR, the implementation should consider putting a maximum cap on the number of entries stored with a reserve list for special or frequently accessed sites. This should be a configuration policy control set by the network administrator who manages ITRs and PTRs. Farinacci, et al. Expires April 14, 2011 [Page 64] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 13. IANA Considerations This section provides guidance to the Internet Assigned Numbers Authority (IANA) regarding registration of values related to the LISP specification, in accordance with BCP 26 and RFC 5226 [RFC5226]. There are two name spaces in LISP that require registration: o LISP IANA registry allocations should not be made for purposes unrelated to LISP routing or transport protocols. o The following policies are used here with the meanings defined in BCP 26: "Specification Required", "IETF Consensus", "Experimental Use", "First Come First Served". 13.1. LISP Address Type Codes Instance ID type codes have a range from 0 to 15, of which 0 and 1 have been allocated [LCAF]. New Type Codes MUST be allocated starting at 2. Type Codes 2 - 10 are to be assigned by IETF Review. Type Codes 11 - 15 are available on a First Come First Served policy. The following codes have been allocated: Type 0: Null Body Type Type 1: AFI List Type See [LCAF] for details for other possible unapproved address encodings. The unapproved LCAF encodings are an area for further study and experimentation. 13.2. LISP UDP Port Numbers The IANA registry has allocated UDP port numbers 4341 and 4342 for LISP data-plane and control-plane operation, respectively. Farinacci, et al. Expires April 14, 2011 [Page 65] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 14. References 14.1. Normative References [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, August 1980. [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", STD 13, RFC 1034, November 1987. [RFC1700] Reynolds, J. and J. Postel, "Assigned Numbers", RFC 1700, October 1994. [RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and E. Lear, "Address Allocation for Private Internets", BCP 5, RFC 1918, February 1996. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2404] Madson, C. and R. Glenn, "The Use of HMAC-SHA-1-96 within ESP and AH", RFC 2404, November 1998. [RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. Traina, "Generic Routing Encapsulation (GRE)", RFC 2784, March 2000. [RFC3056] Carpenter, B. and K. Moore, "Connection of IPv6 Domains via IPv4 Clouds", RFC 3056, February 2001. [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition of Explicit Congestion Notification (ECN) to IP", RFC 3168, September 2001. [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP: Session Initiation Protocol", RFC 3261, June 2002. [RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in IPv6", RFC 3775, June 2004. [RFC4086] Eastlake, D., Schiller, J., and S. Crocker, "Randomness Requirements for Security", BCP 106, RFC 4086, June 2005. [RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing (CIDR): The Internet Address Assignment and Aggregation Plan", BCP 122, RFC 4632, August 2006. Farinacci, et al. Expires April 14, 2011 [Page 66] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 [RFC4634] Eastlake, D. and T. Hansen, "US Secure Hash Algorithms (SHA and HMAC-SHA)", RFC 4634, July 2006. [RFC4866] Arkko, J., Vogt, C., and W. Haddad, "Enhanced Route Optimization for Mobile IPv6", RFC 4866, May 2007. [RFC4984] Meyer, D., Zhang, L., and K. Fall, "Report from the IAB Workshop on Routing and Addressing", RFC 4984, September 2007. [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, May 2008. [RFC5496] Wijnands, IJ., Boers, A., and E. Rosen, "The Reverse Path Forwarding (RPF) Vector TLV", RFC 5496, March 2009. [UDP-TUNNELS] Eubanks, M. and P. Chimento, "UDP Checksums for Tunneled Packets"", draft-eubanks-chimento-6man-00.txt (work in progress), February 2009. 14.2. Informative References [AFI] IANA, "Address Family Indicators (AFIs)", ADDRESS FAMILY NUMBERS http://www.iana.org/numbers.html, Febuary 2007. [ALT] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "LISP Alternative Topology (LISP-ALT)", draft-ietf-lisp-alt-04.txt (work in progress), April 2010. [CHIAPPA] Chiappa, J., "Endpoints and Endpoint names: A Proposed Enhancement to the Internet Architecture", Internet- Draft http://www.chiappa.net/~jnc/tech/endpoints.txt, 1999. [CONS] Farinacci, D., Fuller, V., and D. Meyer, "LISP-CONS: A Content distribution Overlay Network Service for LISP", draft-meyer-lisp-cons-03.txt (work in progress), November 2007. [EMACS] Brim, S., Farinacci, D., Meyer, D., and J. Curran, "EID Mappings Multicast Across Cooperating Systems for LISP", draft-curran-lisp-emacs-00.txt (work in progress), November 2007. [INTERWORK] Lewis, D., Meyer, D., Farinacci, D., and V. Fuller, Farinacci, et al. Expires April 14, 2011 [Page 67] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 "Interworking LISP with IPv4 and IPv6", draft-ietf-lisp-interworking-01.txt (work in progress), March 2010. [LCAF] Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical Address Format", draft-farinacci-lisp-lcaf-02.txt (work in progress), October 2010. [LISA96] Lear, E., Katinsky, J., Coffin, J., and D. Tharp, "Renumbering: Threat or Menace?", Usenix , September 1996. [LISP-MAIN] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "Locator/ID Separation Protocol (LISP)", draft-farinacci-lisp-12.txt (work in progress), March 2009. [LISP-MN] Farinacci, D., Fuller, V., Lewis, D., and D. Meyer, "LISP Mobility Architecture", draft-meyer-lisp-mn-05.txt (work in progress), October 2010. [LISP-MS] Farinacci, D. and V. Fuller, "LISP Map Server", draft-ietf-lisp-ms-05.txt (work in progress), April 2010. [LOC-ID-ARCH] Meyer, D. and D. Lewis, "Architectural Implications of Locator/ID Separation", draft-meyer-loc-id-implications-01.txt (work in progress), Januaryr 2009. [MLISP] Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, "LISP for Multicast Environments", draft-ietf-lisp-multicast-04.txt (work in progress), October 2010. [NERD] Lear, E., "NERD: A Not-so-novel EID to RLOC Database", draft-lear-lisp-nerd-08.txt (work in progress), March 2010. [OPENLISP] Iannone, L. and O. Bonaventure, "OpenLISP Implementation Report", draft-iannone-openlisp-implementation-01.txt (work in progress), July 2008. [RADIR] Narten, T., "Routing and Addressing Problem Statement", draft-narten-radir-problem-statement-00.txt (work in progress), July 2007. Farinacci, et al. Expires April 14, 2011 [Page 68] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 [RFC3344bis] Perkins, C., "IP Mobility Support for IPv4, revised", draft-ietf-mip4-rfc3344bis-05 (work in progress), July 2007. [RFC4192] Baker, F., Lear, E., and R. Droms, "Procedures for Renumbering an IPv6 Network without a Flag Day", RFC 4192, September 2005. [RPMD] Handley, M., Huici, F., and A. Greenhalgh, "RPMD: Protocol for Routing Protocol Meta-data Dissemination", draft-handley-p2ppush-unpublished-2007726.txt (work in progress), July 2007. [VERSIONING] Iannone, L., Saucez, D., and O. Bonaventure, "LISP Mapping Versioning", draft-iannone-lisp-mapping-versioning-02.txt (work in progress), July 2010. Farinacci, et al. Expires April 14, 2011 [Page 69] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 Appendix A. Acknowledgments An initial thank you goes to Dave Oran for planting the seeds for the initial ideas for LISP. His consultation continues to provide value to the LISP authors. A special and appreciative thank you goes to Noel Chiappa for providing architectural impetus over the past decades on separation of location and identity, as well as detailed review of the LISP architecture and documents, coupled with enthusiasm for making LISP a practical and incremental transition for the Internet. The authors would like to gratefully acknowledge many people who have contributed discussion and ideas to the making of this proposal. They include Scott Brim, Andrew Partan, John Zwiebel, Jason Schiller, Lixia Zhang, Dorian Kim, Peter Schoenmaker, Vijay Gill, Geoff Huston, David Conrad, Mark Handley, Ron Bonica, Ted Seely, Mark Townsley, Chris Morrow, Brian Weis, Dave McGrew, Peter Lothberg, Dave Thaler, Eliot Lear, Shane Amante, Ved Kafle, Olivier Bonaventure, Luigi Iannone, Robin Whittle, Brian Carpenter, Joel Halpern, Roger Jorgensen, Ran Atkinson, Stig Venaas, Iljitsch van Beijnum, Roland Bless, Dana Blair, Bill Lynch, Marc Woolward, Damien Saucez, Damian Lezama, Attilla De Groot, Parantap Lahiri, David Black, Roque Gagliano, Isidor Kouvelas, Jesper Skriver, Fred Templin, Margaret Wasserman, Sam Hartman, Michael Hofling, Pedro Marques, Jari Arkko, Gregg Schudel, Srinivas Subramanian, Amit Jain, Xu Xiaohu, Dhirendra Trivedi, Yakov Rekhter, John Scudder, John Drake, Dimitri Papadimitriou, Ross Callon, Selina Heimlich, Job Snijders, and Vina Ermagan. This work originated in the Routing Research Group (RRG) of the IRTF. The individual submission [LISP-MAIN] was converted into this IETF LISP working group draft. Farinacci, et al. Expires April 14, 2011 [Page 70] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 Appendix B. Document Change Log B.1. Changes to draft-ietf-lisp-09.txt o Posted October 2010. o Add to IANA Consideration section about the use of LCAF Type values that accepted and maintained by the IANA registry and not the LCAF specification. o Indicate that implementations should be able to receive LISP control messages when either UDP port is 4342, so they can be robust in the face of intervening NAT boxes. o Add paragraph to SMR section to indicate that an ITR does not need to respond to an SMR-based Map-Request when it has no map-cache entry for the SMR source's EID-prefix. B.2. Changes to draft-ietf-lisp-08.txt o Posted August 2010. o In section 6.1.6, remove statement about setting TTL to 0 in Map- Register messages. o Clarify language in section 6.1.5 about Map-Replying to Data- Probes or Map-Requests. o Indicate that outer TTL should only be copied to inner TTL when it is less than inner TTL. o Indicate a source-EID for RLOC-probes are encoded with an AFI value of 0. o Indicate that SMRs can have a global or per SMR destination rate- limiter. o Add clarifications to the SMR procedures. o Add definitions for "client-side" and 'server-side" terms used in this specification. o Clear up language in section 6.4, last paragraph. o Change ACT of value 0 to "no-action". This is so we can RLOC- probe a PETR and have it return a Map-Reply with a locator-set of size 0. The way it is spec'ed the map-cache entry has action "dropped". Drop-action is set to 3. Farinacci, et al. Expires April 14, 2011 [Page 71] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 o Add statement about normalizing locator weights. o Clarify R-bit definition in the Map-Reply locator record. o Add section on EID Reachability within a LISP site. o Clarify another disadvantage of using anycast locators. o Reworded Abstract. o Change section 2.0 Introduction to remove obsolete information such as the LISP variant definitions. o Change section 5 title from "Tunneling Details" to "LISP Encapsulation Details". o Changes to section 5 to include results of network deployment experience with MTU. Recommend that implementations use either the stateful or stateless handling. o Make clarification wordsmithing to Section 7 and 8. o Identify that if there is one locator in the locator-set of a map- cache entry, that an SMR from that locator should be responded to by sending the the SMR-invoked Map-Request to the database mapping system rather than to the RLOC itself (which may be unreachable). o When describing Unicast and Multicast Weights indicate the the values are relative weights rather than percentages. So it doesn't imply the sum of all locator weights in the locator-set need to be 100. o Do some wordsmithing on copying TTL and TOS fields. o Numerous wordsmithing changes from Dave Meyer. He fine toothed combed the spec. o Removed Section 14 "Prototype Plans and Status". We felt this type of section is no longer appropriate for a protocol specification. o Add clarification text for the IRC description per Damien's commentary. o Remove text on copying nonce from SMR to SMR-invoked Map- Request per Vina's comment about a possible DoS vector. Farinacci, et al. Expires April 14, 2011 [Page 72] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 o Clarify (S/2 + H) in the stateless MTU section. o Add text to reflect Damien's comment about the description of the "ITR-RLOC Address" field in the Map-Request. that the list of RLOC addresses are local addresses of the Map-Requester. B.3. Changes to draft-ietf-lisp-07.txt o Posted April 2010. o Added I-bit to data header so LSB field can also be used as an Instance ID field. When this occurs, the LSB field is reduced to 8-bits (from 32-bits). o Added V-bit to the data header so the 24-bit nonce field can also be used for source and destination version numbers. o Added Map-Version 12-bit value to the EID-record to be used in all of Map-Request, Map-Reply, and Map-Register messages. o Added multiple ITR-RLOC fields to the Map-Request packet so an ETR can decide what address to select for the destination of a Map- Reply. o Added L-bit (Local RLOC bit) and p-bit (Probe-Reply RLOC bit) to the Locator-Set record of an EID-record for a Map-Reply message. The L-bit indicates which RLOCs in the locator-set are local to the sender of the message. The P-bit indicates which RLOC is the source of a RLOC-probe Reply (Map-Reply) message. o Add reference to the LISP Canonical Address Format [LCAF] draft. o Made editorial and clarification changes based on comments from Dhirendra Trivedi. o Added wordsmithing comments from Joel Halpern on DF=1 setting. o Add John Zwiebel clarification to Echo Nonce Algorithm section 6.3.1. o Add John Zwiebel comment about expanding on proxy-map-reply bit for Map-Register messages. o Add NAT section per Ron Bonica comments. o Fix IDnits issues per Ron Bonica. Farinacci, et al. Expires April 14, 2011 [Page 73] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 o Added section on Virtualization and Segmentation to explain the use if the Instance ID field in the data header. o There are too many P-bits, keep their scope to the packet format description and refer to them by name every where else in the spec. o Scanned all occurrences of "should", "should not", "must" and "must not" and uppercased them. o John Zwiebel offered text for section 4.1 to modernize the example. Thanks Z! o Make it more clear in the definition of "EID-to-RLOC Database" that all ETRs need to have the same database mapping. This reflects a comment from John Scudder. o Add a definition "Route-returnability" to the Definition of Terms section. o In section 9.2, add text to describe what the signature of traceroute packets can look like. o Removed references to Data Probe for introductory example. Data- probes are still part of the LISP design but not encouraged. o Added the definition for "LISP site" to the Definition of Terms" section. B.4. Changes to draft-ietf-lisp-06.txt Editorial based changes: o Posted December 2009. o Fix typo for flags in LISP data header. Changed from "4" to "5". o Add text to indicate that Map-Register messages must contain a computed UDP checksum. o Add definitions for PITR and PETR. o Indicate an AFI value of 0 is an unspecified address. o Indicate that the TTL field of a Map-Register is not used and set to 0 by the sender. This change makes this spec consistent with [LISP-MS]. Farinacci, et al. Expires April 14, 2011 [Page 74] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 o Change "... yield a packet size of L bytes" to "... yield a packet size greater than L bytes". o Clarify section 6.1.5 on what addresses and ports are used in Map- Reply messages. o Clarify that LSBs that go beyond the number of locators do not to be SMRed when the locator addresses are greater lexicographically than the locator in the existing locator-set. o Add Gregg, Srini, and Amit to acknowledgment section. o Clarify in the definition of a LISP header what is following the UDP header. o Clarify "verifying Map-Request" text in section 6.1.3. o Add Xu Xiaohu to the acknowledgment section for introducing the problem of overlapping EID-prefixes among multiple sites in an RRG email message. Design based changes: o Use stronger language to have the outer IPv4 header set DF=1 so we can avoid fragment reassembly in an ETR or PETR. This will also make IPv4 and IPv6 encapsulation have consistent behavior. o Map-Requests should not be sent in ECM with the Probe bit is set. These type of Map-Requests are used as RLOC-probes and are sent directly to locator addresses in the underlying network. o Add text in section 6.1.5 about returning all EID-prefixes in a Map-Reply sent by an ETR when there are overlapping EID-prefixes configure. o Add text in a new subsection of section 6.1.5 about dealing with Map-Replies with coarse EID-prefixes. B.5. Changes to draft-ietf-lisp-05.txt o Posted September 2009. o Added this Document Change Log appendix. o Added section indicating that encapsulated Map-Requests must use destination UDP port 4342. Farinacci, et al. Expires April 14, 2011 [Page 75] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 o Don't use AH in Map-Registers. Put key-id, auth-length, and auth- data in Map-Register payload. o Added Jari to acknowledgment section. o State the source-EID is set to 0 when using Map-Requests to refresh or RLOC-probe. o Make more clear what source-RLOC should be for a Map-Request. o The LISP-CONS authors thought that the Type definitions for CONS should be removed from this specification. o Removed nonce from Map-Register message, it wasn't used so no need for it. o Clarify what to do for unspecified Action bits for negative Map- Replies. Since No Action is a drop, make value 0 Drop. B.6. Changes to draft-ietf-lisp-04.txt o Posted September 2009. o How do deal with record count greater than 1 for a Map-Request. Damien and Joel comment. Joel suggests: 1) Specify that senders compliant with the current document will always set the count to 1, and note that the count is included for future extensibility. 2) Specify what a receiver compliant with the draft should do if it receives a request with a count greater than 1. Presumably, it should send some error back? o Add Fred Templin in acknowledgment section. o Add Margaret and Sam to the acknowledgment section for their great comments. o Say more about LAGs in the UDP section per Sam Hartman's comment. o Sam wants to use MAY instead of SHOULD for ignoring checksums on ETR. From the mailing list: "You'd need to word it as an ITR MAY send a zero checksum, an ETR MUST accept a 0 checksum and MAY ignore the checksum completely. And of course we'd need to confirm that can actually be implemented. In particular, hardware that verifies UDP checksums on receive needs to be checked to make sure it permits 0 checksums." o Margaret wants a reference to http://www.ietf.org/id/draft-eubanks-chimento-6man-00.txt. Farinacci, et al. Expires April 14, 2011 [Page 76] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 o Fix description in Map-Request section. Where we describe Map- Reply Record, change "R-bit" to "M-bit". o Add the mobility bit to Map-Replies. So PTRs don't probe so often for MNs but often enough to get mapping updates. o Indicate SHA1 can be used as well for Map-Registers. o More Fred comments on MTU handling. o Isidor comment about spec'ing better periodic Map-Registers. Will be fixed in draft-ietf-lisp-ms-02.txt. o Margaret's comment on gleaning: "The current specification does not make it clear how long gleaned map entries should be retained in the cache, nor does it make it clear how/ when they will be validated. The LISP spec should, at the very least, include a (short) default lifetime for gleaned entries, require that they be validated within a short period of time, and state that a new gleaned entry should never overwrite an entry that was obtained from the mapping system. The security implications of storing "gleaned" entries should also be explored in detail." o Add section on RLOC-probing per working group feedback. o Change "loc-reach-bits" to "loc-status-bits" per comment from Noel. o Remove SMR-bit from data-plane. Dino prefers to have it in the control plane only. o Change LISP header to allow a "Research Bit" so the Nonce and LSB fields can be turned off and used for another future purpose. For Luigi et al versioning convergence. o Add a N-bit to the data header suggested by Noel. Then the nonce field could be used when N is not 1. o Clarify that when E-bit is 0, the nonce field can be an echoed nonce or a random nonce. Comment from Jesper. o Indicate when doing data-gleaning that a verifying Map-Request is sent to the source-EID of the gleaned data packet so we can avoid map-cache corruption by a 3rd party. Comment from Pedro. o Indicate that a verifying Map-Request, for accepting mapping data, should be sent over the ALT (or to the EID). Farinacci, et al. Expires April 14, 2011 [Page 77] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 o Reference IPsec RFC 4302. Comment from Sam and Brian Weis. o Put E-bit in Map-Reply to tell ITRs that the ETR supports echo- noncing. Comment by Pedro and Dino. o Jesper made a comment to loosen the language about requiring the copy of inner TTL to outer TTL since the text to get mixed-AF traceroute to work would violate the "MUST" clause. Changed from MUST to SHOULD in section 5.3. B.7. Changes to draft-ietf-lisp-03.txt o Posted July 2009. o Removed loc-reach-bits longword from control packets per Damien comment. o Clarifications in MTU text from Roque. o Added text to indicate that the locator-set be sorted by locator address from Isidor. o Clarification text from John Zwiebel in Echo-Nonce section. B.8. Changes to draft-ietf-lisp-02.txt o Posted July 2009. o Encapsulation packet format change to add E-bit and make loc- reach-bits 32-bits in length. o Added Echo-Nonce Algorithm section. o Clarification how ECN bits are copied. o Moved S-bit in Map-Request. o Added P-bit in Map-Request and Map-Reply messages to anticipate RLOC-Probe Algorithm. o Added to Mobility section to reference [LISP-MN]. B.9. Changes to draft-ietf-lisp-01.txt o Posted 2 days after draft-ietf-lisp-00.txt in May 2009. o Defined LEID to be a "LISP EID". Farinacci, et al. Expires April 14, 2011 [Page 78] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 o Indicate encapsulation use IPv4 DF=0. o Added negative Map-Reply messages with drop, native-forward, and send-map-request actions. o Added Proxy-Map-Reply bit to Map-Register. B.10. Changes to draft-ietf-lisp-00.txt o Posted May 2009. o Rename of draft-farinacci-lisp-12.txt. o Acknowledgment to RRG. Farinacci, et al. Expires April 14, 2011 [Page 79] Internet-Draft Locator/ID Separation Protocol (LISP) October 2010 Authors' Addresses Dino Farinacci cisco Systems Tasman Drive San Jose, CA 95134 USA Email: dino@cisco.com Vince Fuller cisco Systems Tasman Drive San Jose, CA 95134 USA Email: vaf@cisco.com Dave Meyer cisco Systems 170 Tasman Drive San Jose, CA USA Email: dmm@cisco.com Darrel Lewis cisco Systems 170 Tasman Drive San Jose, CA USA Email: darlewis@cisco.com Farinacci, et al. Expires April 14, 2011 [Page 80]