Internet Draft R. Atkinson draft-rja-ilnp-intro-03.txt Expires: 08 AUG 2010 8 February 2010 Category: Experimental ILNP Concept of Operations draft-rja-ilnp-intro-03.txt Status of this Memo Distribution of this memo is unlimited. 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 Simplified BSD License. This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English. 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 Atkinson Expires in 6 months [Page 1] Internet Draft ILNP Intro 08 FEB 2010 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/1id-abstracts.html The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html Abstract This documents the Concept of Operations for an experimental extension to IPv6 which is known as the Identifier Locator Network Protocol (ILNP). Table of Contents 1. Introduction ...............................................2 2. Transport Protocols.........................................5 3. Mobility....................................................6 4. Multi-Homing................................................8 5. Localised Addressing.......................................10 6. IP Security Enhancements...................................11 7. DNS Enhancements...........................................12 8. Referrals & Application Programming Interfaces.............13 9. Backwards Compatibility....................................14 10. Incremental Deployment.....................................15 11. Implementation Considerations..............................17 12. Security Considerations ...................................18 13. IANA Considerations .......................................22 14. References ................................................22 1. INTRODUCTION At present, the research and development community are exploring various approaches to evolving the Internet Architecture. Several different classes of evolution are being considered. One class is often called "Map and Encapsulate", where traffic would be mapped and then tunnelled through the inter-domain core of the Internet. Another class being considered is sometimes known as "Identifier/Locator Split". This document relates to a proposal that is in the latter class of evoluationary approaches. There has been substantial research relating to naming in the Internet through the years. [IEN 1] [IEN 19] [IEN 23] [IEN 31] [RFC 814] [RFC 1498] More recently, and mindful of that important prior work, the author has been examining enhancements to certain naming aspects of the Internet Architecture. [MobiArch07] Atkinson Expires in 6 months [Page 2] Internet Draft ILNP Intro 08 FEB 2010 [MobiWAC07] [MobiArch08] [MILCOM08] [MILCOM09] [TeleSys] The architectural concept behind ILNP derives originally from a note by Dave Clark to the IETF mailing list suggesting that the IPv6 address be split into separate Identifier and Locator fields. Afterwards, Mike O'Dell persued this concept in Internet-Drafts describing "8+8" or "GSE".[8+8] [GSE] More recently, the IRTF Namespace Research Group (NSRG) studied this matter. Unusually for an IRTF RG, the NSRG operated on the principle that unanimity was required for the NSRG to make a recommendation. The author was a member of the IRTF NSRG. At least one other proposal, the Host Identity Protocol (HIP), also derives in part from the IRTF NSRG studies (and related antecedant work). This current proposal differs from O'Dell's work in various ways. ILNP is an architecture, and can have more than one instantiation. The term ILNPv4 refers precisely to an instance of ILNP that is based upon and backwards compatible with IPv4. The term ILNPv6 refers precisely to an instance of ILNP that is based upon and backwards compatible with IPv6. For the remainder of this document, we simply write the less precise term ILNP, although ILNPv6 is the focus of this document. The crux of this proposal is to have different names for the identity of a node and the location of a node, with crisp semantics for each. ILNPv6 splits the IPv6 address into two separate names: a 64-bit Locator and a 64-bit Identifier. It is worth remembering here that an IPv6 address names a specific interface on a node, since with ILNP the Identifier names a node, not a specific interface on a node. 1 1 2 3 0 4 8 2 6 4 1 +---------------+-----------------+----------------+---------------+ | Version| Traffic Class | Flow Label | +---------------+-----------------+----------------+---------------+ | Payload Length | Next Header | Hop Limit | +---------------+-----------------+--------------------------------+ | Source Address | + + | | + + | | + + | | +---------------+-----------------+----------------+---------------+ Atkinson Expires in 6 months [Page 3] Internet Draft ILNP Intro 08 FEB 2010 | Destination Address | + + | | + + | | + + | | +---------------+-----------------+----------------+---------------+ Figure 1: Existing ("Classic") IPv6 Header The high-order 64-bits of the IPv6 address become the Locator. The Locator indicates the subnetwork point of attachment for a node. In essence, the Locator names a subnetwork. Locators are also known as Routing Prefixes. The low-order 64-bits of the IPv6 address become the Identifier. The Identifier provides a fixed-length identity for a node, rather than an identity for a specific interface of a node. Identifiers are bound to nodes, not to interfaces, and are in the same modified EUI-64 syntax already specified for IPv6.[RFC 2460][RFC 4219][IEEE-EUI] Identifiers can be either globally unique or locally unique. Locally unique Identifiers are unique within the context of their associated Locators. Either globally unique or locally unique Identifiers can be used with this protocol. However, locally unique Identifiers MUST NOT be used with other Locators without first ensuring uniqueness (e.g. by using IPv6 Neighbor Discovery's Duplicate Addess Detection (DAD) mechanism). 1 1 2 3 0 4 8 2 6 4 1 +---------------+-----------------+----------------+---------------+ | Version| Traffic Class | Flow Label | +---------------+-----------------+----------------+---------------+ | Payload Length | Next Header | Hop Limit | +---------------+-----------------+----------------+---------------+ | Source Locator | + + | | +---------------+-----------------+----------------+---------------+ | Source Identifier | + + | | +---------------+-----------------+----------------+---------------+ | Destination Locator | Atkinson Expires in 6 months [Page 4] Internet Draft ILNP Intro 08 FEB 2010 + + | | +---------------+-----------------+----------------+---------------+ | Destination Identifier | + + | | +---------------+-----------------+----------------+---------------+ Figure 2: Enhanced IPv6 Header Most commonly, a node's set of Identifiers are derived from the IEEE 802 or IEEE 1394 MAC addresses associated with that node. This use of MAC addresses to generate Identifiers is convenient and is not required. Other methods also might be used to generate Identifiers. For example, one might derive Identifiers using cryptographic-generation or using methods specified in the IPv6 Privacy Extensions to State-Less Address Auto-Configuration (SLAAC). [RFC 3972, RFC 4941] This proposal enhances the Internet Architecture by adding crisp and clear semantics for the Identifier and for the Locator, removing the semantically-muddled concept of the IP address, and updating end system protocols slightly, without requiring router changes. With these naming enhancements, we have improved the architecture by adding explicit support not only for multi-homing, but also for mobility, localised addressing (e.g. NAT/NAPT), and IP Security. 1.1 Terminology 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 RFC 2119. [RFC 2119] 2. TRANSPORT PROTOCOLS At present, commonly deployed transport protocols include a pseudo-header checksum that includes certain network-layer fields, the IP addresses used for the session, in its calculation. This inclusion of network-layer information within the transport-layer session state creates issues for multi-homing, mobility, IP Security, and localised addressing (e.g. using Network Address Translation). [RFC 1631][RFC 3022] Atkinson Expires in 6 months [Page 5] Internet Draft ILNP Intro 08 FEB 2010 This unfortunate aspect of the TCP pseudo-header checksum has been understood to be an architectural problem at least since 1977, well before the transition from NCP to IPv4.[IEN 1][IEN 19][IEN 23][IEN 31][RFC 1498] With this proposal, transport protocols include only the Identifier in their pseudo-header calculations, but do not include the Locator in their pseudo-header calculations. To minimise the changes required within transport protocol implementations, when this proposal is in use for a communications session, the Locator fields are zeroed for the purpose of transport-layer pseudo-header calculations. Later in this document, methods for incremental deployment of this change and backwards compatibility with non-upgraded nodes are described. 3. MOBILITY First, please recall that mobiity and multi-homing actually present the same set of issues. In each case, the set of Locators associated with a node or site changes. The reason for the change might be different, but the effects on the network and on correspondents is identical. There are no standardised mechanisms to update most transport protocols with new IP addresses in use for the session. Exceptionally, the Stream Control Transport Protocol (SCTP) recently added this capability.[RFC 5061] In July 2008, Mark Handley at UCL proposed adding such a capability to TCP during a presentation at the IRTF Routing RG in Dublin, Ireland. His Multi-Path TCP concept is being considered in the IETF as of this writing. This creates various issues for mobility. For example, there is no method at present to update the IP addresses associated with a transport layer session when one of the nodes in that session moves (i.e. changes one of its points of network attachment). So, the several approaches to IP mobility seek to hide the change in location (and corresponding change in IP addresses) via tunnelling, home agents, foreign agents, and so forth. [RFC 3775] All of this can add substantial complexity to IP mobility approaches, both in the initial deployment and also in ongoing operation. Atkinson Expires in 6 months [Page 6] Internet Draft ILNP Intro 08 FEB 2010 By contrast, this ILNP proposal hides each node's location information from the transport layer protocols at all times, by removing location information from the transport session state (e.g. pseudo-header checksum calculations). In this proposal, mobility and multi-homing are supported using a common set of mechanisms. In both cases, different Locator values are used to identify different IP subnetworks. To handle the move of a node, we add a new ICMP control message. The ICMP Locator Update message is used by a node to inform its existing correspondents that the set of valid Locators for the node has changed. This mechanism can be used to add newly valid Locators, to remove no longer valid Locators, or to do both at the same time. Further, the node uses Secure Dynamic DNS Update to correct the set of L64 records in the DNS for that node. [RFC 3007] This enables any new correspondents to correctly initiate a new session with the node at its new location. This use of DNS for initial rendezvous with mobile node was independently proposed by others [PHG02] and then separately re-invented by the current author later on. (The Locator Update control message could be an entirely new protocol running over UDP, for example, but there is no obvious advantage to creating a new protocol rather than using a new ICMP message.) With ILNP, network mobility (as well as node mobility) is considered a special case of multihoming. That is, when a network moves, it uses a new Locator value for all of its communications sessions. So, the same mechanism, using a new or additional Locator value, also supports network mobility. So in ILNP, when a connectivity change affects the set of valid Locators, the affected node(s) actively: (1) use the ICMP Locator Update message to inform their existing correspondents with the updated information about their currently valid Locator(s). [ILNP-ICMP] AND also (2) update their DNS entries, most commonly by using the Secure Dynamic DNS Update mechanism. [RFC 3007] In the unlikely event of simultaneous motion which changes Atkinson Expires in 6 months [Page 7] Internet Draft ILNP Intro 08 FEB 2010 both nodes' Locators within a very small time period, a node can use the DNS to discover the new Locator value(s) for the other node. As a DNS performance optimisation, the "LP" DNS resource record MAY be used to avoid requiring each node on a subnetwork to update its DNS L64 record entries when that subnetwork's location (e.g. upstream connectivity) changes. In this case, the nodes on the subnetwork each would have an "LP" record pointing to a common domain-name used to name that subnetwork. In turn, that subnetwork's domain name would have one or more L64 record(s) in the DNS. Correspondents of a node on that subnetwork would perform a "L64" record query for that target node (or an "ID" query for that target node) and receive the "LP" records as additional data in the DNS reply. Then the correspondent would perform an L64 record lookup on the domain-name pointed to by that LP record, in order to learn the Locator value to use to reach that target node. For bi-directional flows, such as a TCP session, each node knows whether the current path in use is working by the receiption of data packets, acknowledgements, or both. As with TCP/IP, TCP/ILNP does not need special path probes. UDP/ILNP sessions with acknowledgements work similarly, and also don't need special path probes. In the deployed Internet, the sending node for a UDP/IP session without acknowledgements does not know for certain that all packets are received by the intended receiving node. Such UDP/ILNP sessions fare no worse than UDP/IP sessions. The receiver(s) of such a UDP session SHOULD send a gratuitous IP packet containing an ILNP Nonce option to the sender, in order to enable the receiver to subsequently send ICMP Locator Updates if appropriate. In this last case, UDP/ILNP sessions fare better than UDP/IP sessions, still without using network path probes. One might wonder what happens if a mobile node is moving more quickly than DNS can be updated. This situation is unlikely, particularly given the widespread use of link-layer mobility mechanisms (e.g. GSM, IEEE 802 bridging) in combination with network-layer mobility. However, the situation is functionally equivalent to the situation where a traditional IP node is moving nfaster than the Mobile IPv4 or Mobile IPv6 agents/servers can be updated with the mobile node's new location. So the issue is not new in any way. In all cases, Mobile IPv4 and Mobile IPv6 and ILNP, a node moving that quickly might be temporarily unreachable Atkinson Expires in 6 months [Page 8] Internet Draft ILNP Intro 08 FEB 2010 until it remains at a given network-layer location (e.g. IP subnetwork) long enough for the location update mechanisms (for Mobile IPv4, for Mobile IPv6, or ILNP) to catch up. ILNP is prospectively better than either form of Mobile IP with respect to key management, given that ILNP is using Secure Dynamic DNS Update and given that neither form of Mobile IP has a standardised and scalable key management mechanism at present. 4. MULTI-HOMING Conceptually, there are two kinds of multi-homing. Site multi-homing is when all nodes at a site are multi-homed at the same time. This is what most people mean when they talk about multi-homing. However, there is also a separate concept of node multi-homing, where only a single node is multi-homed. At present, site multi-homing is common in the deployed Internet. This is primarily achieved by advertising the site's routing prefix(es) to more than upstream Internet service provider at a given time. In turn, this requires de-aggregation of routing prefixes within the inter-domain routing system. In turn, this increases the entropy of the inter-domain routing system (e.g. RIB/FIB size increases beyond the minimal RIB/FIB size that would be required to reach all sites). At present, node multi-homing is not common in the deployed Internet. When TCP or UDP are in use for an IP session, node multi-homing cannot provide session resilience, because the transport pseudo-header checksum binds the session to a single interface of the multi-homed node. SCTP has a protocol-specific mechanism to support node multi-homing; SCTP can support session resilience both at present and also without change in the proposed approach. [RFC 5061] In the new scheme, when a node is multi-homed, it has more than one valid Locator value. When one upstream connection fails, the node sends an ICMP Locator Update message to each existing correspondent node to remove the no-longer-valid Locator from the set of valid Locators. [ILNP-ICMP] Also, the node can use Secure Dynamic DNS Update to alter the set of currently valid L64 records associated with that node. [RFC 3007] This second step ensures that any new correspondents can reach the node. In the new scheme, site multi-homing works in a similar manner, with nodes having one Locator for each upstream connection to the Internet. To avoid a DNS Update burst when a site or subnetwork moves location, a DNS record optimisation is Atkinson Expires in 6 months [Page 9] Internet Draft ILNP Intro 08 FEB 2010 possible. This would change the number of DNS Updates required from Order(number of nodes at the site/subnetwork that moved) to Order(1). [ILNP-DNS] Additionally, since the transport-protocol session state no longer includes the Locators, a site could choose to perform Locator rewriting at its site border routers, possibly in combination with applying site traffic engineering policy on which upstream link to use for which packets. Since the site border router(s) are in the middle of any exterior packet flow, they also can send proxy Locator Update messages on behalf of nodes inside that site, and can even include the appropriate Nonce value in such proxy Locator Updates, if desired by that site's administration. 5. LOCALISED ADDRESSING As the Locator value no longer forms part of the node session state (e.g. TCP pseudo-header), it is easier to support localised addressing, which is sometimes also called "Private Addressing", based on the use of local values of the Locator. This would be either in place of, or to supplement, existing NAT-based schemes. [RFC 1631] [RFC 3022] For example, a site that desires to use private addresses internally might deploy IPv6 Unique Local Addressing (ULA) for localised addressing, along with some form of ILNP/ IPv6 Network Address Translation at a site border gateway. [ID-ULA] [RFC 4193] This example is described in detail in [MILCOM09], both as a mechanism for site multi-homing and also as a mechanism to support site-controlled traffic engineering. In the simplest case, an ILNP capable NAT only would need to change the value of the Source Locator in an outbound packet, and the value of the Destination Locator for an inbound packet. Identifier values would not need to change, so a true end-to-end session could be maintained. If a site using localised addressing chooses to deploy a split-horizon DNS server, then the DNS server would advertise the global-scope Locator(s) of the site border routers outside the site to DNS clients outside the site, and would advertise the local-scope Locator(s) specific to that internal node to DNS clients inside the site. Such deployments of split-horizon DNS servers are not unusual in the IPv4 Internet today. If an internal node (e.g. portable computer) moves outside the site, it would follow the normal ILNP methods to update its Atkinson Expires in 6 months [Page 10] Internet Draft ILNP Intro 08 FEB 2010 authoritative DNS server with its current Locator set. In this deployment model, the authoritative DNS server for that mobile device will be either the split-horizon DNS server itself or the master DNS server providing data to the split-horizon DNS server. If a site using localised addressing chooses not to deploy a split-horizon DNS server, then all internal nodes would advertise the global-scope Locator(s) of the site border routers. To deliver packets from one internal node to another internal node, the site would either choose to use layer-2 bridging (e.g. IEEE Spanning Tree, IEEE Rapid Spanning Tree, or a link-state layer-2 algorithm such as the IETF TRILL group or IEEE 802.1 are developing), or the interior routers would forward packets up to the nearest site border router, which in turn would then rewrite the Locators to appropriate local-scope values, and forward the packet towards the interior destination node. We note that a deployment using private/local addressing can also provide site multi-homing by deploying site border routers in this manner. Please note that with this proposal, localised addressing (e.g. using Network Address Translation on the Locator bits) would work in harmony with multihoming, mobility, and IP Security.[MobiWAC07][MILCOM08][MILCOM09] 6. IP SECURITY ENHANCEMENTS A current issue is that the IP Security protocols, AH and ESP, have Security Associations that include the IP addresses of the secure session endpoints. This was understood to be a problem when AH and ESP were originally defined, however the limited set of namespaces in the Internet Architecture did not provide any better choices at that time. Operationally, this binding causes problems for the use of the IPsec protocols through Network Address Translation devices, with mobile nodes (because the mobile node's IP address changes at each network-layer handoff), and with multi-homed nodes (because the session is bound to a particular interface of the multi-homed node, rather than being bound to the node itself).[RFC 3027][RFC 3715] To resolve the issue of IPsec interoperability through a NAT deployment, UDP encapsulation of IPsec is commonly used today.[RFC 3948] Atkinson Expires in 6 months [Page 11] Internet Draft ILNP Intro 08 FEB 2010 With this proposal, the IP Security protocols, AH and ESP, are enhanced to bind Security Associations only to Identifier values and never to Locator values (and also not to an entire 128-bit IPv6 address). Similarly, key management protocols used with IPsec would be enhanced to deprecate use of IP addresses as identifiers and to substitute the use of the new Identifier for that purpose. This small change enables IPsec to work in harmony with multihoming, mobility, and localised addressing. [MILCOM08] [MILCOM09] Further, it would obviate the need for specialised IPsec NAT Traversal mechanisms, thus simplifying IPsec implementations while enhancing deployability and interoperability. [RFC 3948] This change does not reduce the security provided by the IP Security protocols. 7. DNS ENHANCEMENTS As part of this proposal, additional DNS Resource Records have been proposed in a separate document. [ILNP-DNS] These new records store the Identifier and Locator values for nodes that have been upgraded to support the Identifier-Locator Split Mode. With this proposal, mobile or multi-homed nodes and sites are expected to use the existing "Secure Dynamic DNS Update" protocol to keep their Identifier and Locator records correct in its authoritative DNS server(s). [RFC 3007] While some might be surprised, Secure Dynamic DNS Update is available now in a very wide range of existing deployed systems. For example, Microsoft Windows XP (and later versions), the freely distributable BIND DNS software package (used in Apple MacOS X and in most UNIX systems), and the commercial Nominum DNS server all implement support for Secure Dynamic DNS Update and are known to interoperate. [Liu-DNS] There are credible reports that when a site deploys Microsoft's Active Directory, the site (silently) automatically deploys Secure Dynamic DNS Update. [Liu-DNS] So it appears that many sites have already deployed Secure Dynamic DNS Update even though they might not be aware they have already deployed that protocol. [Liu-DNS] Reverse DNS lookups, to find a node's Fully Qualified Domain Name from the combination of a Locator and related Identifier value, can be performed as at present. Atkinson Expires in 6 months [Page 12] Internet Draft ILNP Intro 08 FEB 2010 Previous research by others indicates that DNS caching is largely ineffective, with the exception of NS records and the addresses of DNS servers referred to by NS records.[SBK2002] This means DNS caching performance will not be adversely affected by assigning very short time-to-live (TTL) values to the Locator records of typical nodes. It also means that it is preferable to deploy the DNS server function on nodes that have longer TTL values, rather than on nodes that have shorter TTL values. Identifier values might be very long-lived (e.g. days) when they have been generated from an IEEE MAC Address on the system. Identifier values might have a shorter lifetime (e.g. hours) if they have been cryptographically-generated [RFC 3972], or have been created by the IPv6 Privacy Extensions [RFC 4941], or otherwise have the EUI-64 scope bit at the "local-scope" value. Note that a given ILNP session normally will use a single Identifier value for the life of that session. Existing DNS specifications require that DNS clients and DNS resolvers obey the TTL values provided by the DNS servers. In the context of this proposal, short DNS TTL values are assigned to particular DNS records to ensure that the ubiquitous DNS caching resolvers do not cache volatile values (e.g. Locator records of a mobile node) and consequently return stale information to new requestors. As a practical matter, it is not sensible to flush all Locator values associated with an existing session's remote node from the local node's I/L Session Cache. Instead, Locator values SHOULD be marked as "aged" when their TTL has expired until either the next Locator Update message is received or there is other indication that a given Locator is not working any longer. During a long transition period, a node that is I/L-enabled SHOULD have not only ID and L64 (or ID and LP) records present in its authoritative DNS server, but also SHOULD have AAAA records in the DNS for the benefit of non-upgraded nodes. This capability might be implemented strictly inside a DNS server, whereby the DNS server synthesised a set of AAAA records to advertise from the ID and L64 values that the node has kept updated in that DNS server. Existing DNS specifications require that a DNS resolver or DNS client ignore unrecognised DNS record types. So gratuitously appending ID and L64 records as "additional data" in DNS responses to AAAA queries should not create any operational issues. Atkinson Expires in 6 months [Page 13] Internet Draft ILNP Intro 08 FEB 2010 8. REFERRALS & APPLICATION PROGRAMMING INTERFACES This section is concerned with support for using existing ("legacy") applications over ILNP, including both referrals and APIs. 8.1 BSD Sockets APIs The existing BSD Sockets API can continue to be used with ILNP underneath the API. That API can be implemented in a manner that hides the underlying protocol changes from the applications. For example, the combination of a Locator and an Identifier can be used with the API in the place of an IPv6 address. So it is believed that existing IP address referrals can continue to work properly in most cases. For a rapidly moving target node, referrals might break in at least some cases. The potential for referral breakage is necessarily dependent upon the specific application and implementation being considered. It is suggested, however, that a new, optional, more abstract, C language API be created so that new applications may avoid delving into low-level details of the underlying network protocols. Such an API would be useful today, even with the existing IPv4 and IPv6 Internet, whether or not ILNP were ever widely deployed. 8.2 Java APIs Most existing Java APIs already use abstracted network programming interfaces, for example in the java.Net.URL class. Because these APIs already hide the low-level network-protocol details from the applications, the applications using these APIs (and the APIs themselves) don't need any modification to work equally well with IPv4, IPv6, ILNP, and probably also HIP. 8.3 Referrals in the Future The approach proposed in [ID-Referral] appears to be very suitable for use with ILNP, in addition to being suitable for use with the deployed Internet. Protocols using that approach would not need modification to have their referrals work well with IPv4, IPv6, ILNP, and probably also other network protocols (e.g. HIP). Atkinson Expires in 6 months [Page 14] Internet Draft ILNP Intro 08 FEB 2010 A more sensible approach to referrals would be to use Fully-Qualified Domain Names (FQDNs), as is commonly done today with web URLs. This is approach is highly portable across different network protocols, even with both the IPv4 Internet or the IPv6 Internet. 9. BACKWARDS COMPATIBILITY First, if one comapres Figure 1 and Figure 2, one can see that IPv6 with the Identifier/Locator Split enhancement is fully backwards compatible with existing IPv6. This means that no router software or silicon changes are necessary to support the proposed enhancements. A router would be unaware whether the packet being forwarded were classic IPv6 or the proposed enhanced version of IPv6. So no changes to IPv6 routers is required to deploy this proposal. Further, IPv6 Neighbour Discovery should work fine as is. If a node that has been enhanced to support the Identifier/ Locator Split mode initiates an IP session with another node, normally it will first perform a DNS lookup on the responding node's DNS name. If the inititator node does not find any ID or L64 DNS resource records for the responder node, then the initiator uses the Classical IPv6 mode of operation for the new session with the responder, rather than trying to use the I/L Split mode for that session. If the responder node for a new IP session has not been enhanced to support the I/L Split mode and receives initial packet(s) containing the Nonce Destination Option, the responder will drop the packet and send an ICMP Parameter Problem error message back to the initiator. If the initiator node does not receive a response from the responder in a timely manner (e.g. within TCP timeout for a TCP session) and also does not receive an ICMP Unreachable error message for that packet, OR if the initiator receives an ICMP Parameter Problem error message for that packet, then the initiator knows that the responder is not able to support the I/L Split Operating mode. In this case, the initiator node SHOULD try again to create the new IP session but this time OMITTING the Nonce Destination Option, and this time operating in Classic IPv6 mode, rather than I/L Split mode. Finally, since an ILNP node is also a fully-capable IPv6 node, then the upgraded node can use any standardised IPv6 mechanisms Atkinson Expires in 6 months [Page 15] Internet Draft ILNP Intro 08 FEB 2010 for communicating with a legacy IPv6 node (i.e. an IPv6 node without ILNP capability enhancements). So ILNP will in no case be worse than existing IPv6, and in many cases ILNP will out perform existing IPv6. 10. INCREMENTAL DEPLOYMENT If a node has been enhanced to support the Identifier/ Locator Split operating mode, that node's fully-qualified domain name will normally have one or more ID records and one or more L64 records associated with it in the DNS. When a host ("initiator") initiates a new IP session with a correspondent ("responder"), it normally will perform a DNS lookup to determine the address(es) of the responder. A host that has been enhanced to support the Identifier/ Locator Split operating mode normally will look for Identifier ("ID") and Locator ("L64") records in any received DNS replies. DNS servers that support ID and L64 records SHOULD include them (when they exist) as additional data in all DNS replies to queries for DNS AAAA records.[ILNP-DNS] If the initiator supports the I/L Split mode and from DNS information learns that the responder also supports the I/L Split mode, then the initiator will generate an unpredictable nonce value, store that value in a local Correspondent Cache, and will include the Nonce Destination Option in its initial packet(s) to the responder.[ILNP-Nonce] If the responder supports the I/L Split mode and receives initial packet(s) containing the Nonce Destination Option, the responder will thereby know that the initiator supports the I/L Split mode and the responder will also operate in I/L Split mode for this new IP session. If the responder supports the I/L Split mode and receives initial packet(s) NOT containing the Nonce Destination Option, the responder will thereby know that the initiator does NOT support the I/L Split mode and the responder will operate in classic IPv6 mode for this new IP session. The previous section described how interoperability between enhanced nodes and non-enhanced nodes is retained even if a non-enhanced node erroneously has ID and/or L64 DNS resource records in place (e.g. due to some accident). The mobility capabilities of ILNP might be the most important in the deployment world. Despite substantial good efforts by many, Atkinson Expires in 6 months [Page 16] Internet Draft ILNP Intro 08 FEB 2010 neither Mobile IPv4 nor Mobile IPv6 are widely used at present. However, much of the recent work in operating systems has focused on support for mobile devices (e.g. mobile telephone handsets, hand-held music players, hand-held organisers). Those devices probably represent the fastest growth segment of the Internet at present. Moreover, many vendors of such devices have included significant networking protocol improvements in incremental operating system updates, rather than always waiting for a new major release to add networking facilities. However, other users or vendors might be more interested by the new security models enabled by having Identifiers different from Locators, or they might be more interested in the ability to provide node-specific multi-homing, rather than always multi-homing an entire site. In the end, the marketplace has myriad users with various functional needs. The set of improvements offered by ILNP is broad, and should appeal to a wide range of vendors and users. 11. IMPLEMENTATION CONSIDERATIONSa This section discusses implementation considerations that are not otherwise discussed in the ILNP Internet-Drafts. 11.1 ILNP Session Cache An ILNP-capable node will need to modify its network protocol implementation to add an ILNP Session Cache. In theory, this cache is within the ILNP network-layer. However, many network protocol implementations do not have strict protocol separation or layering. In the interest of efficient implementation, and to avoid unduly restricting implementers, an ILNP implementation is not required to limit the accessibility of ILNP Session Cache to the network-layer. The ILNP Session Cache contains at least the following inter-related data elements: Set of Local Locator(s) Set of Correspondent' Locator(s) Set of Local Identifier(s) Set of Correspondent's Identifier(s) Nonce used from the local node to that correspondent Nonce used from that correspondent to the local node Valid Time Lookups in the ILNP Session Cache use an (Correspondent Identifier, Nonce) tuple as a lookup key. This facilitates situations where, perhaps due to deployment of Local-scope Identifiers, more than one correspondent node is using the same Atkinson Expires in 6 months [Page 17] Internet Draft ILNP Intro 08 FEB 2010 Identifier value. The Valid Time field holds the (UTC) time (measured as seconds since January 1st 1970, as with Network Time Protocol) through which this ILNP session information is valid. A table entry entry is current if the node's current time is less than or equal to the time in the Valid Time field, while a table entry is aged if the node's current time is greater than the time in the Valid Time field. 12. SECURITY CONSIDERATIONS This proposal outlines a proposed evolution for the Internet Architecture to provide improved capabilities. This section discusses security considerations for this proposal. 12.1 Authentication of Locator Updates A separate document [ILNP-Nonce] proposed a new IPv6 Destination Option that can be used to carry a session nonce end-to-end between communicating nodes. That nonce provides protection against off-path attacks on an Identifier/Locator session. The Nonce Destination Option is used ONLY for IP sessions in the Identifier/Locator Split mode. Ordinary IPv6 is vulnerable to on-path attacks unless the IP Authentication Header or IP Encapsulating Security Payload is in use. So the Nonce Destination Option only seeks to provide protection against off-path attacks on an IP session -- equivalent to ordinary IPv6 when not using IP Security. When the Identifier/Locator split mode is in use for an existing IP session, the Nonce Destination Option MUST be included in any ICMP control messages (e.g. ICMP Unreachable, ICMP Locator Update) sent with regard to that IP session. It is common to have non-symmetric paths between two nodes on the Internet. To reduce the number of on-path nodes that know the Nonce value for a given session when the I/L split mode is in use, a nonce value is unidirectional, not bidirectional. For example, for a session between two nodes A and B, one nonce value is used from A to B and a different nonce value is used from B to A. When in the I/L Split operating mode for an existing IP session, ICMP control messages received without a Nonce Destination Option MUST be discarded as forgeries. This Atkinson Expires in 6 months [Page 18] Internet Draft ILNP Intro 08 FEB 2010 security event SHOULD be logged. When in the I/L Split operating mode for an existing IP session, ICMP control messages received without a correct nonce value inside the Nonce Destination Option MUST be discarded as forgeries. This security event SHOULD be logged. When in the I/L Split operating mode for an existing IP session, and a node changes its Locator set, it should include the Nonce Destination Option in the first few data packets sent using a new Locator value, so that the recipient can validate the received data packets as valid (despite having an unexpected Source Locator value). For ID/Locator Split mode sessions operating in higher risk environments, the use of the cryptographic authentication provided by IP Authentication Header is recommended *in addition* to concurrent use of the Nonce Destination Option. It is important to note that at present an IPv6 session is entirely vulnerable to on-path attacks unless IPsec is in use for that particular IPv6 session, so the security properties of the new proposal are never worse than for existing IPv6. 12.2 Forged Identifier Attacks In the deployed Internet, active attacks using packets with a forged Source IP Address have been publicly known at least since early 1995.[CA-1995-01] While these exist in the deployed Internet, they have not been widespread. This is equivalent to the issue of a forged Identifier value and demonstrates that this is not a new threat created by the Identifier/Locator-split mode of operation. One mitigation for these attacks has been to deploy Source IP Address Filtering.[RFC 2827] [RFC 3704] Jun Bi at U. Tsinghua cites Arbor Networks as reporting that this mechanism has less than 50% deployment and cites an MIT analysis indicating that at least 25% of the deployed Internet permits forged source IP addresses. Other parts of this document discuss the probability of an accidental duplicate Identifier being used on the Internet. However, this sub-section instead focuses on methods for mitigating attacks based on packets containing deliberately forged Source Identifier values. Atkinson Expires in 6 months [Page 19] Internet Draft ILNP Intro 08 FEB 2010 First, the recommendations of [RFC 2827] & [RFC 3704] remain. So any packets that have a forged Locator value can be easily filtered using existing widely available mechanisms. Second, the receiving node does not blindly accept any packet with the proper Source Identifier and proper Destination Identifier as an authentic packet. Instead, each node operating the I/L-split mode maintains a session cache for each of its correspondents, as described above. This cache contains two unidirectional nonce values (one used in control messages sent by this node, a different one used to authenticate messages from the other node). The cache also contains the currently valid set of Locators and set of Identifiers for each correspondent node. If a received packet contains valid Identifier values and a valid Destination Locator, but contains a Source Locator value that is not present in the session cache, the packet is dropped without further processing as an invalid packet, unless the packet also contains a Nonce Destination Option with the correct value used for packets from the node with that Source Identifier to this node. This prevents an off-path attacker from stealing an existing session. Third, any node can distinguish different nodes using the same Identifier value by other properties of their sessions. IPv6 Neighbor Discovery prevents more than one node from using the same source (Locator + Identifier) pair at the same time. So cases of different nodes using the same Identifier value will involve nodes that have different sets of valid Locator values. A node can thus demux based on the combination of Source Locator and Source Identifier if necessary. If IP Security is in use, the combination of the Source Identifier and the SPI value would be sufficient to demux two different sessions. Finally, deployments in high threat environments also SHOULD use the IP Authentication Header to authenticate control traffic and data traffic. Because in the I/L-split mode, IP Security binds only to the Identifier values, and never to the Locator values, this enables a mobile or multi-homed node to use IPsec even when its Locator value(s) have just changed. 12.3 IP Security Enhancements The IP Security standards are enhanced here by binding IPsec Security Associations to the Identifiers of the session endpoints, rather than binding IPsec Security Associations to the IP Addresses as at present. This change enhances the deployability and interoperability of the IP Security standards, but does not decrease the security provided by those protocols. Atkinson Expires in 6 months [Page 20] Internet Draft ILNP Intro 08 FEB 2010 Also, the IP Authentication Header omits the Source Locator and Destination Locator fields from its authentication calculations when ILNP is in use. This enables IP AH to work well even through a NAT or other situation where a Locator value might change during transit. 12.4 DNS Security The DNS enhancements proposed here are entirely compatible with, and can be protected using, the existing IETF standards for DNS Security.[RFC 4033] The Secure DNS Dynamic Update mechanism used here is also used unchanged.[RFC 3007] So there is no change to the security properties of the Domain Name System or of DNS servers due to ILNP. 12.5 Firewall Considerations In the proposed new scheme, firewalls are able to authenticate ICMP control messages arriving on the external interface. This enables more thoughtful handling of ICMP messages by firewalls than is commonly the case at present. As the firewall is along the path between the communicating nodes, the firewall can snoop on the Session Nonce being carried in the initial packets of an I/L Split mode session. The firewall can verify that nonce is present on incoming control packets, dropping any control packets that lack the correct nonce value. By always including the nonce, even when IP Security is also in use, the firewall can filter out all off-path attacks. In this case, a forged packet from an on-path attacker will still be detected when the IPsec input processing occurs in the receiving node; this will cause that forged packet to be dropped rather than acted upon. 12.6 Neighbor Discovery Authentication Nothing in this proposal prevents sites from using the Secure Neighbor Discovery (SEND) proposal for authenticating IPv6 Neighbor Discovery. [RFC 3971] 12.7 Site Topology Obfuscation A site that wishes to obscure its internal topology information MAY do so by deploying site border routers that rewrite the Locator values for the site as packets enter or leave the site. For example, a site might choose to use a ULA prefix internally for this reason.[RFC 4193] [ID-ULA] In this case, the site border Atkinson Expires in 6 months [Page 21] Internet Draft ILNP Intro 08 FEB 2010 routers would rewrite the Source Locator of ILNP packets leaving the site to a global-scope Locator associated with the site. Also, those site border routers would rewrite the Destination Locator of packets entering the site from the global-scope Locator to an appropriate interior ULA Locator for the destination node.[MILCOM08] 12.8 Path Liveness Some perceive that an Identifier-Locator Split architecture creates a new issue that is sometimes called "Locator Liveness" or "Path Liveness". This refers to the question of whether an IP packet with a particular destination Locator value will be able to reach the intended destination or not, given that some otherwise valid paths might be unusable by the sending node (e.g. due to security policy or other administrative choice). In fact, this issue has existed in the IPv4 Internet for decades. For example, an IPv4 server might have multiple valid IP addresses, each advertised to the world via an DNS "A" record. However, at a given moment in time, it is possible that a given sending node might not be able to use a given (otherwise valid) destination IPv4 address in an IP packet to reach that IPv4 server. So we see that using an Identifier/Locator Split architecture does not create this issue, nor does it make this issue worse than it is with the deployed IPv4 Internet. In ILNP, the same conceptual approach described in [RFC 5534] can be reused. Alternatively, an ILNP node can reuse the existing IPv4 methods for determining whether a given path to the target destination is currently usable, which existing methods leverage session state information that the communicating end systems are already keeping (e.g. for transport-layer protocol reasons). Last, it is important for the reader to understand that the mechanism described in [ILNP-ICMP] is a performance optimisation, significantly shortening the layer-3 handoff time if/when a correspondent changes location. Architecturally, using ICMP is no different from using UDP, of course. 13. IANA CONSIDERATIONS This document has no IANA considerations. 14. REFERENCES Atkinson Expires in 6 months [Page 22] Internet Draft ILNP Intro 08 FEB 2010 This section provides both normative and informative references relating to this note. 14.1. Normative References [RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC 2460] S. Deering & R. Hinden, "Internet Protocol Version 6 Specification", RFC-2460, December 1998. [RFC 3007] B. Wellington, "Secure Domain Name System Dynamic Update", RFC-3007, November 2000. [RFC 4033] R. Arends, et alia, "DNS Security Introduction and Requirements", RFC-4033, March 2005. [RFC 4219] R. Hinden & S. Deering, "IP Version 6 Addressing Architecture", RFC-4219, February 2006. 14.2. Informative References [8+8] M. O'Dell, "8+8 - An Alternate Addressing Architecture for IPv6", Internet-Draft, October 1996. [CA-1995-01] US CERT, "IP Spoofing Attacks and Hijacked Terminal Connections", CERT Advisory 1995-01, Issued 23 JAN 1995, Revised 23 SEP 1997. [GSE] M. O'Dell, "GSE - An Alternate Addressing Architecture for IPv6", Internet-Draft, February 1997. [ID-ULA] R. Hinden, G. Huston, & T. Narten, "Centrally Assigned Unique Local IPv6 Unicast Addresses", draft-ietf-ipv6-ula-central-02.txt, 15 June 2007. [ID-Referral] B. Carpenter and others, "A Generic Referral Object for Internet Entities", draft-carpenter-behave-referral-object-01, 20 October 2009. [IEEE-EUI] IEEE Standards Association, "Guidelines for 64-bit Global Identifier (EUI-64)", IEEE, Atkinson Expires in 6 months [Page 23] Internet Draft ILNP Intro 08 FEB 2010 2007. [IEN 1] C.J. Bennett, S.W. Edge, & A.J. Hinchley, "Issues in the Interconnection of Datagram Networks", Internet Experiment Note (IEN) 1, INDRA Note 637, PSPWN 76, University College London, London, England, UK, WC1E 6BT, 29 July 1977. http://www.postel.org/ien/ien001.pdf [IEN 19] J. F. Shoch, "Inter-Network Naming, Addressing, and Routing", IEN-19, January 1978. [IEN 23] J. F. Shoch, "On Names, Addresses, and Routings", IEN-23, January 1978. [IEN 31] D. Cohen, "On Names, Addresses, and Routings (II)", IEN-31, April 1978. [ILNP-Nonce] R. Atkinson, "Nonce Destination Option", draft-rja-ilnp-nonce-02.txt, February 2010. [ILNP-DNS] R. Atkinson, "Additional DNS Resource Records", draft-rja-ilnp-dns-02.txt, February 2010. [ILNP-ICMP] R. Atkinson, "ICMP Locator Update message" draft-rja-ilnp-icmp-01.txt, February 2010. [Liu-DNS] C. Liu & P. Albitz, "DNS & Bind", 5th Edition, O'Reilly & Associates, Sebastopol, CA, USA, May 2006. ISBN 0-596-10057-4 [MobiArch07] R. Atkinson, S. Bhatti, & S. Hailes, "Mobility as an Integrated Service Through the Use of Naming", Proceedings of ACM MobiArch 2007, August 2007, Kyoto, Japan. [MobiArch08] R. Atkinson, S. Bhatti, & S. Hailes, "Mobility Through Naming: Impact on DNS", Proceedings of ACM MobiArch 2008, August 2008, Seattle, WA, USA. [MobiWAC07] R. Atkinson, S. Bhatti, & S. Hailes, "A Proposal for Unifying Mobility with Multi-Homing, NAT, & Security", Proceedings of ACM MobiWAC 2007, Chania, Crete. ACM, October 2007. Atkinson Expires in 6 months [Page 24] Internet Draft ILNP Intro 08 FEB 2010 [MILCOM08] R. Atkinson, S. Bhatti, & S. Hailes, "Harmonised Resilience, Security, and Mobility Capability for IP", Proceedings of IEEE Military Communications (MILCOM) Conference, San Diego, CA, USA, November 2008. [MILCOM09] R. Atkinson, S. Bhatti, & S. Hailes, "Site-Controlled Secure Multi-Homing and Traffic Engineering For IP", Proceedings of IEEE Military Communications (MILCOM) Conference, Boston, MA, USA, October 2009. [PHG02] Pappas, A, S. Hailes, & R. Giaffreda, "Mobile Host Location Tracking through DNS", Proceedings of IEEE London Communications Symposium, IEEE, September 2002, London, England, UK. [SBK2002] Alex C. Snoeren, Hari Balakrishnan, & M. Frans Kaashoek, "Reconsidering Internet Mobility", Proceedings of 8th Workshop on Hot Topics in Operating Systems, 2002. [RFC 814] D.D. Clark, "Names, Addresses, Ports, and Routes", RFC-814, July 1982. [RFC 1498] J.H. Saltzer, "On the Naming and Binding of Network Destinations", RFC-1498, August 1993. [RFC 1631] K. Egevang & P. Francis, "The IP Network Address Translator (NAT)", RFC-1631, May 1994. [RFC 2827] P. Ferguson & D. Senie, "Network Ingress Filtering: Defeating Denial of Service Attacks which employ IP Source Address Spoofing", RFC-2827, May 2000. [RFC 3022] P. Srisuresh & K. Egevang, "Traditional IP Network Address Translator", RFC-3022, January 2001. [RFC 3027] M. Holdrege and P Srisuresh, "Protocol Complications of the IP Network Address Translator", RFC-3027, January 2001. [RFC 3704] F. Baker & P. Savola, "Ingress Filtering for Multihomed Networks, RFC-3704, March 2004. [RFC 3715] B. Aboba and W. Dixon, "IPsec-Network Address Atkinson Expires in 6 months [Page 25] Internet Draft ILNP Intro 08 FEB 2010 Translation (NAT) Compatibility Requirements", RFC-3715, March 2004. [RFC 3775] D. Johnson, C. Perkins, and J. Arkko, "Mobility Support in IPv6", RFC-3775, June 2004. [RFC 3948] A. Huttunen, et alia, "UDP Encapsulation of IPsec ESP Packets", RFC-3948, January 2005. [RFC 3971] J. Arkko, J. Kempf, B. Zill, & P. Nikander, "SEcure Neighbor Discovery (SEND)", RFC-3971 March 2005. [RFC 3972] T. Aura, "Cryptographically Generated Addresses (CGAs)", RFC-3972, March 2005. [RFC 4193] R. Hinden & B. Haberman, "Unique Local IPv6 Unicast Addresses, RFC-4193, October 2005. [RFC 4941] T. Narten, R. Draves, & S. Krishnan, "Privacy Extensions for Stateless Address Autoconfiguration in IPv6", RFC-4941, September 2007. [RFC 5061] R. Stewart, Q. Xie, M. Tuexen, S. Maruyama, & M. Kozuka, "Stream Control Transmission Protocol (SCTP) Dynamic Address Reconfiguration", RFC-5061, September 2007. [RFC 5534] J. Arkko & I. van Beijnum, "Failure Detection and Locator Pair Exploration Protocol for IPv6 Multihoming", RFC-5534, June 2009. [TeleSys] R. Atkinson, S. Bhatti, & S. Hailes, "ILNP: Mobility, Multi-Homing, Localised Addressing and Security Through Naming", Telecommunications Systems, Volume 42, Number 3-4, pp 273-291, Springer-Verlag, December 2009, ISSN 1018-4864. ACKNOWLEDGEMENTS Saleem Bhatti, Steve Hailes, Joel Halpern, Mark Handley, Tony Li, and Yakov Rehkter (in alphabetical order) provided review and feedback on earlier versions of this document. AUTHOR'S ADDRESS R. Atkinson McLean, VA, USA Atkinson Expires in 6 months [Page 26] Internet Draft ILNP Intro 08 FEB 2010 Email: rja.lists@gmail.com Expires: 08 AUG 2010 Atkinson Expires in 6 months [Page 27]