Network Working Group P. Marques Internet-Draft Contrail Systems Intended status: Standards Track L. Fang Expires: April 02, 2013 Cisco Systems P. Pan Infinera Corp A. Shukla Juniper Networks M. Napierala AT&T Labs N. Bitar Verizon October 2012 BGP-signaled end-system IP/VPNs. draft-ietf-l3vpn-end-system-00 Abstract This document describes a solution in which the control plane protocol specified in BGP/MPLS IP VPNs [RFC4364] is used to provide a Virtual Network service to end-systems. These end-systems may be used to provide network services or may directly host end-to-end applications. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on April 02, 2013. Copyright Notice Copyright (c) 2012 IETF Trust and the persons identified as the Marques, et al. Expires April 02, 2013 [Page 1] Internet-Draft BGP-signaled end-system IP/VPNs October 2012 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. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 2 2. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Applicability of BGP IP VPNs . . . . . . . . . . . . . . . . . 4 4. Virtual network end-points . . . . . . . . . . . . . . . . . . 6 5. VPN Forwarder . . . . . . . . . . . . . . . . . . . . . . . . 8 6. XMPP signaling protocol . . . . . . . . . . . . . . . . . . . 10 7. End-System Route Server behavior . . . . . . . . . . . . . . . 15 8. Operational Model . . . . . . . . . . . . . . . . . . . . . . 15 9. Security Considerations . . . . . . . . . . . . . . . . . . . 18 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 19 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19 11.1. Normative References . . . . . . . . . . . . . . . . . . 19 11.2. Informational References . . . . . . . . . . . . . . . . 19 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20 1. Introduction This document describes the requirements for a network virtualization solution that provides an IP service to end-system virtual interfaces. It then discusses how the BGP IP VPNs [RFC4364] control plane can be used to provide a solution that meets these requirements. Subsequent sections provide a detailed discussion of the control and forwarding plane components. In BGP IP VPNs, Customer Edge (CE) interfaces connect to a Provider Edge (PE) device which provides both the control plane and VPN encapsulation functions required to implement a Virtual Network service. This document decouples the control plane and forwarding functionality of the PE device in order to enable the forwarding functionality to be implemented in multiple devices. For instance, the forwarding function can be implemented directly on the operating system of application servers or network appliances. 1.1. Terminology This document makes use of the following terms: End-System Route Server A software application that implements the control plane functionality of a BGP IP VPN PE device and a XMPP server that interacts with VPN Forwarders. Marques, et al. Expires April 02, 2013 [Page 2] Internet-Draft BGP-signaled end-system IP/VPNs October 2012 Virtual Interface An interface in an end-system that is used by a virtual machine or by applications. It performs the role of a CE interface in a BGP IP VPN network. VPN Forwarder The forwarding component of a BGP IP VPN PE device. This functionality may be co-located with the virtual interface or implemented by an external device. 2. Requirements Network Virtualization is used in both service provider as well as enterprise networks to support multi-tenancy, network-based access control. It may also be used to facilitate end-system mobility. Multi-tenancy allows a physical network to provide services to multiple "customers" or "tenants", whether these are external entities in the case of a Service Provider providing managed VPN services or internal departments sharing an IT facility. Multi- tenancy requires isolation of traffic and routing information between tenants. Within a tenant, it is often required to create multiple distinct virtual networks, in order to be able to provide network-based access control. In this service model, each virtual network behaves as a "Closed User Group" (CUG) of end-systems that are allowed to exchange traffic freely, while traffic between virtual networks is subject to access controls. This scenario can be found in both enterprise campus networks, branch offices and data-centers. It is often the case when network access control is used, that the traffic patterns are such that there is significantly more traffic crossing a CUG boundary than staying within such boundary. As an example, in campus networks it is common to segregate users into CUGs based on some classification such as the user's department. Campus networks often see traffic patterns in which almost all the traffic flows northbound to the data-center or internet boundaries. Similar traffic patterns can be found in multi-tier applications in IT data- centers. End-systems are often configured to expect the concept of IP subnet to match its closed user group. A network virtualization solution should be able to provide this concept of IP subnet regardless of whether the underlying implementation uses a multi-access network or not. End-system virtual interfaces should be able to directly access multiple closed user groups without needing to traverse a gateway. Network access policy should allow this access whether the source and destination CUGs for a particular traffic flow belong to the same tenant or different tenants. It is often the case that infrastructure services are provided to multiple tenants. One such example is voice-over-IP gateway services for branch offices. Marques, et al. Expires April 02, 2013 [Page 3] Internet-Draft BGP-signaled end-system IP/VPNs October 2012 Independently, but often associated with the previous two functions, IP mobility is another network function that can be implemented using network virtualization. By abstracting the externally visible network address from the underlying infrastructure address, mobility can be implemented without having to recur to home agents or large L2 broadcast domains. Alternative techniques that are used in both Service Provider as well as enterprise networks. IP Mobility requires the ability to "move" a device without disrupting its TCP (or UDP) transport sessions. These sessions often deploy second or sub-second keepalives to detect application failure. Experience with failure restoration in Service Provider networks shows that fast-failure restoration often requires the pre- provisioning of a restoration path. IP Mobility can be a result of devices physically moving (e.g., a WiFi enabled laptop) or workload being diverted between physical systems such as network appliances or application servers. 3. Applicability of BGP IP VPNs BGP IP VPNs [RFC4364] is the industry de-facto standard for providing "closed user group" functionality in WAN environments. It is used by service providers in environments where several millions of routes are present. It supports both isolated VPNs as well as overlapping VPNs (often referred to as "extranets"). In its traditional usage in Service Provider networks, BGP IP VPN functionality is implemented in a Provider Edge (PE) device that combines both BGP signaling as well as VRF-based forwarding functions. In practice, most PE devices in current use are multi- component systems with the signaling and forwarding functionality actually implemented in different processors attached to an internal network. This document assumes a similar separation of functionality in which software appliances, the End-System Route Servers, implement the control plane functionality of a PE device and a VPN Forwarder implements the forwarding function usually found in a PE device "line-card". The VPN Forwarder functionality may be co-located with the end-system virtual interface (e.g., implemented in the hypervisor switch or host OS network drivers). It may also be external to the end-system residing in a data-center switch or specialized appliance. Operationally, BGP IP VPN technology has several important characteristics: It has a high-level of aggregation between customer interfaces and managed entities (Provider Edge devices). Marques, et al. Expires April 02, 2013 [Page 4] Internet-Draft BGP-signaled end-system IP/VPNs October 2012 It defines VPNs as policies, allowing an interface to directly exchange traffic with multiple VPNs and allowing for the topology of the virtual network to be modified by modifying the policy configuration. It scales horizontally in terms of event propagation. By increasing the number of signaling devices implementing the PE control plane, it is possible to decrease the load on each signaling device when it comes to propagating events that originate in a specific location and must be propagated across the network. The last point is particularly relevant to the convergence characteristics required for large scale deployments. BGP's hierarchical route distribution capabilities allow a deployment to divide the workload by increasing the number of End-System Route Servers. As an example consider a topology in which 100 End-System Route Servers are deployed in a network each serving a subset of the VPN forwarding elements. The Route Servers inter-connect to two top- level BGP Route Reflectors [RFC4456]. If an event (i.e. a VPN route change) needs to be propagated from a specific end-system to 10.000 clients randomly distributed across the network, each of the End-System Route Servers must generate 100 updates to its respective downstream clients. By modifying this topology such that another 100 End-System Route Servers are added, then each Route Server is now responsible to generate 50 client updates. This example illustrates the linear scaling properties of BGP: doubling the number of Route Servers (i.e. the processing capacity) reduces in half the number of updates generated by each (i.e. load at each processing node). The same horizontal scaling techniques can be applied to the Route Reflector layer in the example above by subsetting the VPN Route space according to some pre-defined criteria (for instance VPN route target) and using a pair of Route Reflectors per subset. In the previous example we assumed a dense membership in which all Route Servers have local clients that are interested in a particular event. BGP also optimizes the route distribution for sparse events. Marques, et al. Expires April 02, 2013 [Page 5] Internet-Draft BGP-signaled end-system IP/VPNs October 2012 The Route Target Constraint [RFC4684] extension, builds an optimal distribution tree for message propagation based on VPN membership. It ensures that only the PEs with local receivers for a particular event do receive it also decreasing the total load on the upstream BGP speaker. In the WAN environment, BGP IP VPN control plane scaling is focused not primarily on route convergence times but on memory footprint of embedded devices. While memory footprint does not have a similar linear scaling behavior, memory technology available to software appliances is often at 10x the scale of what is commonly found in WAN environments. The functionality present in the BGP IP VPN control plane addresses the requirements specified in the previous section. Specifically, it supports multiple potentially overlapping "groups", regular or "hub and spoke" topologies and the scaling characteristics necessary. The BGP IP VPN control plane supports not only the definition of "closed user-groups" (VPNs in its terminology) but also the propagation of inter-VPN traffic policies [RFC5575]. An application of that mechanism to "end-system" VPNs is presented in [I-D.marques- sdnp-flow-spec]. Note that the signaling protocol itself is rather agnostic of the encapsulation used on the wire as long as this encapsulation has the ability to carry a 20 bit label. Several network environments use a network infrastructure that is only capable of providing an IP unicast service. In order to support them, implementations of this document should support the MPLS in GRE [RFC4023] encapsulation. Other encapsulations are possible, including UDP based encapsulations. 4. Virtual network end-points This document assumes that end-systems support one or more virtual network interfaces in addition to a physical interface that is associated with the underlying network infrastructure. Virtual network interfaces can be associated with a restricted list of applications via OS-dependent mechanisms, a Virtual Machine (VM), or they can be used to provide network connectivity to all user applications in the same way that a "VPN tunnel" interface is used to provide access between an end-system (e.g., a laptop) and a remote corporate network. From an IP address assignment point of view, a virtual network interface is addressed out of the virtual IP topology and associated with a "closed user group" or VPN, while the physical interface of the machine is addressed in the network infrastructure topology. As a security measure, it is recommended that virtual and infrastructure topologies never be allowed to exchange traffic directly. Marques, et al. Expires April 02, 2013 [Page 6] Internet-Draft BGP-signaled end-system IP/VPNs October 2012 Both static and dynamic IP address allocation can be supported. The later assumes that the VPN Forwarder implements a DHCP relay or DHCP proxy functionality. A virtual network interface is connected to a VPN Forwarder. This VPN Forwarder MAY be co-located in the end-system or external. Traffic that ingresses or egresses through a virtual network interface is routed at the VPN Forwarder which acts as the first-hop router (in the virtual topology). The IP configuration on the client side of this virtual network interface (e.g., in the guest OS) can follow one of two models: point-to-point interface model. multipoint interface model. In a point-to-point interface model, the VPN client routing table (e.g., on the guest OS) contains the following routing entires: a host route to the local IP address, a host route to the first-hop router via the virtual interface and a default route to the first-hop router. This is the model typically used in "VPN tunnel" configurations or other access technologies such as cable deployments or DSL. When this model is used, the first-hop router IP address is a link-local address that is the same on all first-hop routers across a specific deployment. This first-hop IP address should not change when a virtual interface moves between different machines. In a multi-point interface model, the VPN client routing table (e.g., on the guest OS) contains the following routing entires: a host route to the local IP address, a subnet route to the local interface and optionally a default route to a specific router address within that subnet. In this model, the VPN client IP stack will issue address resolution requests for any IP addresses it considers to be directly attached to the subnet. The VPN Forwarder shall answer all address resolution requests with a virtual MAC address which SHOULD be the same across all VPN Forwarders in a specific deployment. This virtual MAC address SHALL default to the VRRP [RFC5798] virtual router MAC address for Virtual Router Identifier (VRID) 1. When the virtual topology first-hop router resides on the same physical machine, the host OS is responsible to map the virtual interface with a VPN specific routing table (without taking L2 addresses into consideration). In this case the mac-addresses known to the guest OS are not used on the wire. When the virtual topology first-hop router resides in an external system (e.g., the first hop-switch) the virtual interface shall be identified by the combination of the mac-address assigned to physical interface of the end-system and a 802.1Q VLAN tag. The first-hop switch should use a virtual router MAC address to answer any address resolution queries. Marques, et al. Expires April 02, 2013 [Page 7] Internet-Draft BGP-signaled end-system IP/VPNs October 2012 Whenever an external VPN Forwarder is used and resiliency is desired, the external VPN Forwarder should be redundant. It is desirable to use VRRP as a mechanism to control the flow of traffic between the end-system and the external VPN Forwarder. VRRP already defines the necessary procedures to elect a single forwarder for a LAN. This specification uses the VRRP virtual router MAC address as the default L2 address for the VPN Forwarder as a client virtual interface may move between locations where redundancy may not be present. While the VRRP Virtual Router MAC will be used to answer any address resolution request made by the virtual interface client (e.g., the guest VM) this does not imply that a single default router is elected per virtual IP subnet. The ingress VPN Forwarder will perform an IP forwarding decision based on the destination IP address of the (payload) traffic. VRRP router election is only relevant in selecting the VPN Forwarder associated with a specific machine, when external forwarders are in use. 5. VPN Forwarder In this solution, the Host OS/Hypervisor in the end-system must participate in the virtual network service. Given an end-system with multiple virtual interfaces, these virtual interfaces must be mapped onto the network by the guest OS such that applications on one virtual interface are not allowed to impersonate another virtual interface. When VPN forwarder functionality is implemented by the Host OS/ Hypervisor, intermediate systems in the network do not require any knowledge of the virtual network topology. This can simplify the design and operation of the physical network. When it is not possible or desirable to add the VPN forwarding functionality to the end-system, it may be implemented by an external system, typically located as close as possible to the end-system itself. Both models, co-located and external VPN Forwarder can co-exist in a deployment. In order to implement the BGP IP VPN Forwarder functionality a device MUST implement the following functionality: Support for multiple "Virtual Routing and Forwarding" (VRF) tables; Marques, et al. Expires April 02, 2013 [Page 8] Internet-Draft BGP-signaled end-system IP/VPNs October 2012 VRF route entries map prefixes in the virtual network topology to a next-hop containing a infrastructure IP address and a 20-bit label allocated by the destination Forwarder. The VRF table lookup follows the standard IP lookup (best-match) algorithm. Associate an end-system virtual interface with a specific VRF table; When the the Forwarder is co-located with the end-system, this association is implemented by an internal mechanism. When the Forwarder is external the association is performed using the mac-address of the end-system and a IEEE 802.1Q tag that identifies the virtual interface within the end-system. Encapsulate outgoing traffic (end-system to network) according to the result of the VRF lookup; Associate incoming packets (network to end-system) to a VRF according to the 20-bit label contained immediately after the GRE header; The VPN Forwarder MAY support the ability to associate multiple virtual interfaces with the same VRF. When that is the case, locally originated routes, that is IP routes to the local virtual interfaces SHALL NOT be used to forward outbound traffic (from the virtual interfaces to the outside) unless a route advertisement has been received that matches that specific IP prefix and next-hop information. As an example, if a given VRF contains two virtual interfaces, "veth0" and "veth1", with the addresses 10.0.1.1/32 and 10.0.1.2/32 respectively, the initial forwarding state must be initialized such that traffic from either of these interfaces does not match the other's routing table entry. It may for instance match a default route advertised by a remote system. Traffic received from other VPN Forwarders, however, must be delivered to the correct local interface. If at a subsequent stage a route is received from the Route Server such that 10.0.1.2/32 has a next-hop with the IP address of the local host and the correct label, the system may subsequently install a local routing table entry that delivers traffic directly to the "veth1" interface. The 20-bit label which is associated with a virtual-interface is of local significance only and SHOULD be allocated by the VPN Forwarder. When an external VPN Forwarder is used the end-system MUST associate each virtual interface with a VLAN [IEEE.802-1Q] that is unique on the end-system. The switching infrastructure MUST be configured such that multi-destination frames sourced from an end-system are only delivered to VPN Forwarders used by this end-system and not to other end-systems. Marques, et al. Expires April 02, 2013 [Page 9] Internet-Draft BGP-signaled end-system IP/VPNs October 2012 6. XMPP signaling protocol End-System Route Servers must be aware of VPN membership on each Forwarder as well as what IP addresses are currently associated with each virtual interface. VPN Forwarders must receive VPN route information from which to populate their forwarding tables. External VPN Forwarders also need to receive the virtual interface and IP address events from the end- system for which they are VPN forwarders. In this case the end- system assigns an 802.1Q VLAN tag to each virtual interface and communicates that information to the Forwarder. In order to exchange this information this specification uses the XMPP [RFC6120] protocol along with the PubSub Collection Nodes [pubsub] extension. When an external VPN Forwarder is used, end-systems establish XMPP sessions with VPN Forwarders. VPN forwarders (both co-located and external) establish XMPP sessions with End-System Route Servers. VPN Forwarders act as an XMPP clients of a End-System Route Server. External VPN Forwarders act as XMPP servers for end-systems which are associated with them. These sessions are persistent and MUST use the XMPP Ping [xmpp-ping] extension in order to detect end-system failures. A VPN Forwarder MAY connect to multiple End-System Route Servers for reliability. In this case it SHOULD publish its information to each of the Route Servers. It MAY choose to subscribe to VPN routing information once only from one of the available gateways. The information advertised by an XMPP client SHOULD be deleted after a configurable timeout, when the session closes. This timeout should default to 60 seconds. +---------+ +--------+ | RS | ----------- | BGP | +---------+ +--------+ // \ / XMPP \ / // \ / +------------+ \ / | end-system | \ / +------------+ \/ \\ /\ XMPP / \ \\ / \ +---------+ / \ +--------+ | RS | ----------- | BGP | +---------+ +--------+ Marques, et al. Expires April 02, 2013 [Page 10] Internet-Draft BGP-signaled end-system IP/VPNs October 2012 The figure above represents a typical configuration in which an end- system with a co-located VPN Forwarder is directly connected to two End-System Routes Servers, which are in turn connected to multiple BGP speakers which may be other L3VPN PEs or BGP route reflectors. In deployment the number of End-System Route Servers used will depend on the desired Route Server to VPN Forwarder ratio which affects the convergence time of event propagation. The XMPP "jid" used by the client shall be a 6-byte value that uniquely identifies it in its administrative domain. This specification recommends the use of the MAC address of one of the physical ethernet interfaces. Each VPN shall be identified by a 128 octet ASCII character string. When external Forwarders are used, its control software operates as a XMPP server processing requests from end-systems and as a client of one or more End-System Route Servers. The control software relays to the End-System Route Server(s) VPN membership messages it receives from the end-system. VPN routing information received from the Route Server(s) SHOULD NOT be propagated to the end-system. When a virtual interface is created on a end-system, the host operating-system software shall generate an XMPP Subscribe message to its server (the End-System Route Server or external VPN Forwarder). Subscription request from co-located VPN Forwarder to Route Server: The request above, instructs the End-System Route Server to start populating the client's VRF table with any routing information that is available for this VPN. The XMPP node 'vpn-customer-name' is assumed to be a collection which is implicitly created by the End- System Route Server. Creation of a virtual interface may precede any IP address becoming active on the interface, as it is the case with VM instantiation. Subscription request from end-system to external VPN Forwarder: Marques, et al. Expires April 02, 2013 [Page 11] Internet-Draft BGP-signaled end-system IP/VPNs October 2012 vlan-id When an external VPN Forwarder is used the end-system should include the VLAN identifier it assigned to the virtual interface as a subscription option. When a IP address is added to a virtual interface, the end-system will generate an XMPP Publish request. Publish request from VPN Forwarder to End-System Route Server: Marques, et al. Expires April 02, 2013 [Page 12] Internet-Draft BGP-signaled end-system IP/VPNs October 2012 to='network-control.domain.org' id='request1'> 1
'vpn-ip-address/32'
1
'infrastructure-ip-address'
1
The End-System Route Server will convert the information received in a the 'publish' request into the corresponding BGP route information such that:. It associates the specific request with a local VRF which it resolves by using a combination of the originator system-id and the collection 'node' attribute. It creates a BGP VPN route with a 'Route Distinguisher' (RD) which contains the the end-system's 'system-id' value and the specified IP prefix and 'label' received from the VPN Forwarder as the Network Layer Reachability Information (NLRI). The BGP next-hop address is set to the address of the VPN Forwarder. It optionally associates the route with an extended community TDB containing a version number of the virtual-interface. Marques, et al. Expires April 02, 2013 [Page 13] Internet-Draft BGP-signaled end-system IP/VPNs October 2012 Update notification from Route Server to VPN Forwarder: 1
'vpn-ip-address>/32'
1
'infrastructure-ip-address'
1
...
Notifications should be generated whenever a VPN route is added, modified or deleted. Note that the Update from the Route Server to the VPN Forwarder does not contain the system-id of the destination end-system. The "from" attribute in the 'message' element contains a "jid" associated with the Route Servers in the domain. The XMPP messages are point-to- point in nature, between a Forwarder and Route Server. Even in the case when one XMPP publish request from a Forwarder may cause the Route Server to generate one or more event notifications. When multiple possible routes exist for a given VPN IP address within a VRF it is the responsibility of the Route Server to select the best path to advertise to the Forwarder. When routes are withdrawn, the End-System Route Server generates both a "collection disassociate" request as well as a node "delete" request. In situations where an automated system is controlling the instantiation of virtual interfaces it may be possible to have that system assign a non-decreasing version number for each instantiation of that particular interface. In that case, this number, carried in the 'version' field may be used to help gateways select the most recent instantiation of an interface during the interval of time where multiple routes are present. Marques, et al. Expires April 02, 2013 [Page 14] Internet-Draft BGP-signaled end-system IP/VPNs October 2012 7. End-System Route Server behavior End-System Route Servers SHALL support the BGP address families: VPN- IPv4 (1, 128), VPN-IPv6 (2, 128) and RT-Constraint (1, 132) [RFC4684]. When an End-System Route Server receives a request to create or modify a VPN route it SHALL generate a BGP VPN route advertisement with the corresponding information. It is assumed that the End-System Route Servers have information regarding the mapping between end-system tuple ('system-id', 'vpn- customer-names') and BGP Route Targets used to import and export information from the associated VRFs. This mapping is known via an out-of-band mechanism not specified in this document. Whenever the End-System Route Server receives an XMPP subscription request, it SHALL consult its RT-Constraint Routing Information Base (RIB). If the Route Server does not already have locally originated route for the route target the corresponds to the vpn-name present in the request, it SHALL create one and generate the corresponding BGP route advertisement. This route advertisement should only be withdrawn when there are no more downstream XMPP clients subscribed to the VPN. The 32bit route version number defined in the XML schema is advertised into BGP as an Extended community with type TBD. End-System Route Servers SHOULD automatically assign a BGP route distinguisher per VPN routing table. 8. Operational Model In the simplest case, a VPN is a collection of systems that are allowed to exchange traffic with each other and only with each other. Since all the forwarding tables in this VPN have the same routing entries they are often referred to as symmetrical VPNs. In order to better illustrate the operation of the protocol we consider a simple example in which "host 1" and "host 2" both contain a virtual interface that is a member of the same VPN. Each of these hosts has an XMPP session with an End-System Route Server, RS1 and RS2 our example, and these Route Servers are part of the same BGP mesh. When a virtual interface is created on "host 1", the local XMPP client generates a XMPP subscription message to its respective Route Server. This message contains a VPN identifier that has been assigned by the provisioning system. The Route Server maps that identifier to a BGP IP VPN configuration which contains the list of import and export route targets to be used for that particular VRF. Marques, et al. Expires April 02, 2013 [Page 15] Internet-Draft BGP-signaled end-system IP/VPNs October 2012 Once the interface is operational, "host 1" will publish any IP addresses that are configured on the respective virtual interface. This will in turn cause the End-System Route Server to advertise these (directly or indirectly) to any other BGP speaker on the network which is connected to an attachment point of that VPN. +--------+ +------------+ +----------+ | host 1 | <===> | End-System | <===> | BGP mesh | +--------+ |Route Server| +----------+ +------------+ +----------------+-------------+-------+-----------+ | VPN IP address | NEXT-HOP | label | Known via | +----------------+-------------+-------+-----------+ | 10.1.1.1/32 | 192.168.1.1 | 10000 | XMPP | | 10.1.1.2/32 | 192.168.2.1 | 20000 | BGP | +----------------+-------------+-------+-----------+ VPN Routing table on Route Server The figure above represents the contents of the VRF routing table on RS1 after the IPv4 address 10.1.1.1 has been added to the virtual interface on host 1. It assumes that there is another attachement point for this VPN with the IPv4 address of 10.1.1.2. Host 1 has an infrastructure IP address of 192.168.1.1 configured on its physical interface while host 2 has IP address 192.168.2.1. The contents of the VRF routing table in the End-System Route Servers are advertised via XMPP Update notifications sent to host 1. This information is the used by the host to populate the forwarding table associated with that VPN. +--------+ +--------+ app -- veth0 --| host 1 |=== [network] ===| host 2 |-- veth0 -- app +--------+ +--------+ IP pkt ===> GRE encap ===> [IP net] ===> GRE decap ===> IP pkt [192.168.2.1, 20] map 20 to veth0 +----------------+--------------+-------+ | VPN IP address | Host address | label | +----------------+--------------+-------+ | 10.1.1.1/32 | localhost | 10000 | | 10.1.1.2/32 | 192.168.2.1 | 20000 | +----------------+--------------+-------+ VRF table on host1 When an application that uses the virtual interface on host 1 generates packets with a destination IP address of 10.1.1.2 these are routed by the VPN Forwarder implemented in the Host OS. The packets are encapsulated with a GRE header that contains a 20-bit label assigned by host 2. Marques, et al. Expires April 02, 2013 [Page 16] Internet-Draft BGP-signaled end-system IP/VPNs October 2012 In the case the virtual interface on host is associated with a guest OS, this guest OS has had its address resolution queries answered with the Virtual Router MAC address. As a result, that is the address it uses as the destination MAC address in packets it originates. This MAC address is not present on the GRE encapsulated packet. End-System Route Servers are software applications the implement both the BGP IP VPN PE control plane as well as XMPP server functionality. These application are not in the forwarding plane and do not need to be co-located with a network device. Network devices MAY have direct BGP sessions to the End-System Route Servers. For instance, a router or security appliance that supports BGP/MPLS IP VPNs over GRE may use its existing functionality to inter-operate directly with a collection of Virtual Machines or other network appliances that support this specification. End-System Route Servers implement the VRF import policy and export policy functionality that is associated with PE routers in standard BGP IP/VPN deployments. VPN Forwarders receive forwarding information after policy and route selection is applied. These are unqualified routes in a specific VRF rather than VPN routing information qualified by a Route Distinguisher and with a set of Route Targets. A symmetrical VPN uses a vrf import and vrf export polices that contain a single route target, where the route target used for both import and export is the same. Different VPN topologies can be created by manipulating the vrf import and export configuration including "hub-and-spoke" topologies or overlapping VPNs. Marques, et al. Expires April 02, 2013 [Page 17] Internet-Draft BGP-signaled end-system IP/VPNs October 2012 An example of a hub-and-spoke VPN configuration is one where all the traffic from the VPN clients must be redirected though a middle-box for inspection. Assuming that the virtual interfaces of a particular user are configured to be in the VPN "tenant1". At an initial stage this "tenant1" VPN is symmetrical and uses a single Route Target in both its import and export policies. The middle-box functionality can be incrementally deployed by defining a new VPN, "tenant1-hub", and an associated Route Target. Accompanied with a change in the End-System Route Server configuration such that VPN "tenant1" only imports routes with the Route Target associated with the hub. The "hub" VPN is assumed to advertise a prefix that covers all the VPN clients IP addresses. The "hub" VPN imports the VPN routes in order for it to be able to generate the XMPP updates to the "hub" end- system. This information is required for the return traffic from the hub to the spokes (the VPN clients). In such a scenario a single physical interface can connect the middle-box to the clients in a given VPN which appear logically as downstream from it. Such a middle-box would often require connectivity to multiple VPNs, such as for instance an "outside" VPN which provides external connectivity to one or more "inside" VPNs. The functionality defined in this document in which the BGP IP VPN PE functionality is split into its control (End-System Route Servers) and forwarding (VPN Forwarder) components is fully interoperable with existing BGP IP VPN PEs. This makes it possible to reuse existing systems. For example, at the edge of a data-center facility it may be desirable to use an existing router or appliance that aggregates IP VPN routing information and/or provides IP based services such as stateful packet inspection. Such a system can be configured, based on existing functionality, to suppress more specific routes than a specified aggregate while advertising the aggregate with a BGP NEXT_HOP containing the PE's IP address and a locally assigned label corresponding to a VRF where the more specific routes are present. 9. Security Considerations The signaling protocol defines the access control policies for each virtual interface and any guest application associated with it. It is important to secure the end-system access to End-System Route Servers and the BGP infrastructure itself. The XMPP session between end-systems and the Route Servers MUST use mutual authentication. One possible strategy is to distribute pre- signed certificates to end-systems which are presented as proof of authorization to the Route Server. Marques, et al. Expires April 02, 2013 [Page 18] Internet-Draft BGP-signaled end-system IP/VPNs October 2012 BGP sessions MUST be authenticated. This document recommends that BGP speaking systems filter traffic on port 179 such that only IP addresses which are known to participate in the BGP signaling protocol are allowed. 10. Acknowledgements Yakov Rekhter has contributed to this document by providing detailed feedback and suggestions. The authors would also like to thank Thomas Morin for his comments. 11. References 11.1. Normative References [RFC4023] Worster, T., Rekhter, Y. and E. Rosen, "Encapsulating MPLS in IP or Generic Routing Encapsulation (GRE)", RFC 4023, March 2005. [RFC4271] Rekhter, Y., Li, T. and S. Hares, "A Border Gateway Protocol 4 (BGP-4)", RFC 4271, January 2006. [RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private Networks (VPNs)", RFC 4364, February 2006. [RFC4456] Bates, T., Chen, E. and R. Chandra, "BGP Route Reflection: An Alternative to Full Mesh Internal BGP (IBGP)", RFC 4456, April 2006. [RFC4684] Marques, P., Bonica, R., Fang, L., Martini, L., Raszuk, R., Patel, K. and J. Guichard, "Constrained Route Distribution for Border Gateway Protocol/MultiProtocol Label Switching (BGP/MPLS) Internet Protocol (IP) Virtual Private Networks (VPNs)", RFC 4684, November 2006. [RFC5575] Marques, P., Sheth, N., Raszuk, R., Greene, B., Mauch, J. and D. McPherson, "Dissemination of Flow Specification Rules", RFC 5575, August 2009. [RFC5798] Nadas, S., "Virtual Router Redundancy Protocol (VRRP) Version 3 for IPv4 and IPv6", RFC 5798, March 2010. [RFC6120] Saint-Andre, P., "Extensible Messaging and Presence Protocol (XMPP): Core", RFC 6120, March 2011. [xmpp-ping] "XMPP Ping", XEP 0199, June 2009. [pubsub] "PubSub Collection Nodes", XEP 0248, September 2010. 11.2. Informational References [I-D.marques-sdnp-flow-spec] Marques, et al. Expires April 02, 2013 [Page 19] Internet-Draft BGP-signaled end-system IP/VPNs October 2012 Marques, P., Fang, L., Pan, P., Shukla, A. and M. Napierala, "Traffic classification in end-system IP VPNs.", Internet-Draft draft-marques-sdnp-flow-spec-01, April 2012. [IEEE.802-1Q] Institute of Electrical and Electronics Engineers, "Local and Metropolitan Area Networks: Virtual Bridged Local Area Networks", IEEE Std 802.1Q-2005, May 2006. Authors' Addresses Pedro Marques Contrail Systems 2350 Mission College Blvd. Santa Clara, CA 95054 Email: roque@contrailsystems.com Luyuan Fang Cisco Systems 111 Wood Avenue South Iselin, NJ 08830 Email: lufang@cisco.com Ping Pan Infinera Corp 140 Caspian Ct. Sunnyvale, CA 94089 Email: ppan@infinera.com Amit Shukla Juniper Networks 1194 N. Mathilda Av. Sunnyvale, CA 94089 Email: amit@juniper.net Maria Napierala AT&T Labs 200 Laurel Avenue Middletown, NJ 07748 Email: mnapierala@att.com Marques, et al. Expires April 02, 2013 [Page 20] Internet-Draft BGP-signaled end-system IP/VPNs October 2012 Nabil Bitar Verizon 40 Sylvan Rd. Waltham, MA 02145 Email: nabil.bitar@verizon.com Marques, et al. Expires April 02, 2013 [Page 21]