Network Working Group A. Bashandy Internet Draft Cisco Systems Intended status: Standards Track October 26, 2011 Expires: April 2012 Scalable BGP FRR Protection against Edge Node Failure draft-bashandy-bgp-edge-node-frr-01.txt Abstract Consider a BGP free core scenario. Suppose the edge BGP speakers PE1, PE2,..., PEn know about a prefix P/p via the external routers CE1, CE2,..., CEm. If the edge router PEi crashes or becomes totally disconnected from the core, it desirable for a penultimate hop route "P" carrying traffic to the failed edge router PEi to immediately restore traffic by re-tunneling packets originally tunneled to PEi and destined to the prefix P/p to one of the other edge routers that advertised P/p, say PEj, until BGP re-converges. In doing so, it is highly desirable to keep the core BGP-free while not imposing restrictions on external connectivity. Thus (1) a core router should not be required to learn any BGP prefix, (2) the size of the forwarding and routing tables in the core routers should be independent of the number of BGP prefixes,(3) there should be no special router (or group of routers) that handles restoring traffic, and (4) there should be no restrictions on what edge routers advertise what prefixes. For labeled prefixes, (5) the penultimate hop router must swap the label advertised by the failed edge router PEi for the prefix P/p with the label advertised for the same prefix by the edge router PEj before re-tunneling the packet to PEj Status of this Memo 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. 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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...................................................3 1.1. Problem definition........................................4 1.2. Conventions used in this document.........................5 1.3. Terminology...............................................5 2. Control Plane Operation........................................6 2.1. Control plane Operation for unlabeled prefixes............6 2.1.1. Step 1: Calculation of the Repair PE.................7 2.1.2. Step 2: Assigning and Advertising the BGP Next-hop...7 2.1.3. Step 3: Informing Core Routers about the Repair PE...7 2.1.4. Step 4: How a P router (a core router) Programs its Forwarding Plane............................................8 Bashandy Expires April 26, 2012 [Page 2] Internet-Draft BGP FRR using Repair Label October 2011 2.2. Control plane Operation for Labeled Prefixes..............8 2.2.1. Step 1: Calculation of the Repair PE.................9 2.2.2. Step 2: Assigning and Advertising the BGP Next-hop...9 2.2.3. Step 3: Informing core routers about the repair path.9 2.2.4. Step 4: How a P router (a core router) programs its forwarding plane...........................................10 2.3. Rules for a choosing Repair path.........................11 2.3.1. General Rules for Choosing and Programming the Repair Path.......................................................11 2.3.2. Rules for Choosing the Repair Path for Labeled Prefixes ...........................................................11 2.4. Forwarding Plane Operation...............................12 2.4.1. For unlabeled prefix................................12 2.4.2. For Labeled prefix..................................13 3. Example.......................................................14 4. Security Considerations.......................................16 5. IANA Considerations...........................................16 6. Conclusions...................................................16 7. References....................................................16 7.1. Normative References.....................................16 7.2. Informative References...................................16 8. Acknowledgments...............................................17 1. Introduction In a BGP free core, where traffic is tunneled between edge routers, BGP speakers advertise reachability information about prefixes. For labeled address families, namely AFI/SAFI 1/4, 2/4, 1/128, and 2/128, an edge router assigns local labels to prefixes and associates the local label with each advertised prefix such as L3VPN [6], 6PE [7], and Softwire [5]. Suppose that a given edge router is chosen as the best next-hop for a prefix P/p. An ingress router that receives a packet from an external router and destined for the prefix P/p "tunnels" the packet across the core to that egress router. If the prefix P/p is a labeled prefix, the ingress router pushes the label advertised by the egress router before tunneling the packet to the egress router. Upon receiving the packet from the core, the egress router takes the appropriate forwarding decision based on the content of the packet or the label pushed on the packet. In modern networks, it is not uncommon to have a prefix reachable via multiple edge routers. One example is the best external path [4]. Another more common and widely deployed scenario is L3VPN [6][6] with multi-homed VPN sites. As an example, consider the L3VPN topology depicted in Figure 1. Bashandy Expires April 26, 2012 [Page 3] Internet-Draft BGP FRR using Repair Label October 2011 PE1 \ \ \ \ CE1....... VPN prefix / (10.0.0.0/8) / / / BGP free core P--------PE0 \ \ \ \ CE2....... VPN prefix / (20.0.0.0/8) / / / PE2 Figure 1 VPN prefix reachable via multiple PEs As illustrated in Figure 1, the edge router PE0 is the primary NH for both 10.0.0.0/8 and 20.0.0.0/8. At the same time, both 10.0.0.0/8 and 20.0.0.0/8 are reachable through the other edge routers PE1 and PE2, respectively. 1.1. Problem definition The problem that we are trying to solve is as follows o Even though multiple prefixes may share the same egress router, they have different backup edge router. In Figure 1 above, both 10.0.0.0/8 and 20.0.0.0/8 share the same primary next hop PE0, the routing protocol(s) must identify that the node protecting loop free alternate for 10.0.0.0/8 is PE1 while the node protecting loop free alternate for 11.0.0.0/8 is PE2 o On loosing connection to the edge router, the core router "P" needs to redirect traffic towards the "correct" backup edge router without waiting for IGP or BGP to re-converge and update the routing tables. On the failure of PE0 illustrated in Figure 1, the core router P MUST reroute traffic for 10.0.0.0/8 towards PE1 and traffic for 11.0.0.0/8 towards PE2 Bashandy Expires April 26, 2012 [Page 4] Internet-Draft BGP FRR using Repair Label October 2011 o The core router P MUST NOT be forced to learn about the BGP prefixes on any of the edge routers. The same applies for all core routers. o There SHOULD NOT be a need for a special router or group of routers to handle rerouting traffic on edge node failure. o The size of the routing table on any core router MUST be independent of the number of BGP prefixes in the network. o For labeled prefixes, the core router MUST swap the label advertised by egress edge router (PE0 in Figure 1) with the label advertised by the backup router (PE1 and PE2 in Figure 1). 1.2. Conventions used in this document 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 [1]. In this document, these words will appear with that interpretation only when in ALL CAPS. Lower case uses of these words are not to be interpreted as carrying RFC-2119 significance. 1.3. Terminology This section outlines the terms used in this document. For ease of use, we will use terms similar to those used by L3VPN [6] o BGP-Free core: A network where BGP prefixes are only known to the edge routers and traffic is tunneled between edge routers o Protected prefix: It is a prefix P/p (of any AFI) that a BGP speaker has an external path to. The BGP speaker may learn about the prefix from an external peer through BGP, some other protocol, or manual configuration. The protected prefix is advertised to some or all the internal peers. o Primary egress PE: It is an IBGP peer that can reach the protected prefix P/p through an external path and advertised the prefix to the other IBGP peers. The primary egress PE was chosen as the best path by one or more internal peers. In other words, the primary egress PE is an egress PE that will normally be used by some ingress PEs when there is no failure. Referring to Figure 1, PE0 is a primary egress PE. Bashandy Expires April 26, 2012 [Page 5] Internet-Draft BGP FRR using Repair Label October 2011 o Primary next-hop: It is an IPv4 or IPv6 host address belonging to the primary egress PE. If the prefix is advertised via BGP, then the primary next-hop is the next-hop attribute in the BGP update message [2][3]. o CE: It is an external router through which an egress PE can reach a prefix P/p. The routers "CE1" and "CE2" in Figure 1 are examples of such CE. o Ingress PE: It is a BGP speaker that learns about a prefix through another IBGP peer and chooses that IBGP peer as the next-hop for the prefix. o Repairing P router: A core router that attempts to restore traffic when the primary egress PE is no longer reachable without waiting for IGP or BGP to re-converge. The repairing P router restores the traffic by rerouting the traffic (through a tunnel) towards the pre-calculated repair PE when it detects that the primary egress PE is no longer reachable. Referring to Figure 1, the router "P" is the repairing P router. o Repair egress PE: It is an egress PE other than the primary egress PE that can reach the protected prefix P/p through an external neighbor. The repair PE is pre-calculated via other PEs prior to any failure. Referring to Figure 1, PE1 is the repair PE for 10.0.0.0/8 while PE2 is the repair PE for 20.0.0.0/8. o Protected egress PE: Any primary egress PE protected by a repairing P router. o Protected edge router: Any protected egress PE. o Repair path: It is the repair egress PE. If the protected prefix is a labeled prefix, the repair path is the repair egress PE together with the label that will be pushed when the repairing P router reroutes traffic to the repair PE. 2. Control Plane Operation This section specifies the control plane operation needed to solve the problem mentioned in the Introduction. 2.1. Control plane Operation for unlabeled prefixes This section specifies the operation of the control plane for AFI/SAFI 1/1, 2/1, 1/2, and 2/2 The control plane operation can be summarized in 4 steps: Bashandy Expires April 26, 2012 [Page 6] Internet-Draft BGP FRR using Repair Label October 2011 1. Calculation of the repair PE 2. Assigning and advertising the next-hop for protected prefixes 3. Informing core routers about repair PEs 4. How a P router (a core router) programs its forwarding plane 2.1.1. Step 1: Calculation of the Repair PE 1. Consider the prefix P/p learnt by an egress edge router PEi via an external neighbor. The edge router advertises the prefix P/p to some or all of its IBGP peers 2. The edge router PEi MAY choose a repair PE for the external prefix P/p. Section 2.3. specifies the rules for choosing the repair edge router PEj. 3. In the end, an egress edge route PEi will have a repair edge router PEj for some or all prefixes that PEi has external path(s) to. 2.1.2. Step 2: Assigning and Advertising the BGP Next-hop 1. An edge router PEi groups the set of prefixes that have a repair PE as follows: Two prefixes belong to the same group if they share the same repair PE 2. For each group, the PE assigns a local next-hop. Thus if a prefix P/p belongs to group Gi, its primary next-hop is NHi. For example, the PE assigns a different loopback interface address as the next-hop for each of the groups of prefixes. 3. When advertising the prefix and its primary next-hop to its IBGP peers, the PE router uses NHi as the next-hop attribute of prefixes belonging to the group Gi 2.1.3. Step 3: Informing Core Routers about the Repair PE 1. In step 2 (Section 2.1.2. ) the egress PE assigns a primary next-hop NHi for protected prefixes belonging to group Gi. 2. The primary next-hop NHi is advertised to the core using IGP as usual Bashandy Expires April 26, 2012 [Page 7] Internet-Draft BGP FRR using Repair Label October 2011 3. The repair next-hop is the next-hop attribute advertised for the prefix P/p by the repair edge router PEj. Let's denote the repair next-hop for prefixes belonging to group Gi by "rNHi". Because rNHi is the next-hop advertised by the repair PE, rNHi will also be known to all core routers via IGP 4. The egress PE MUST advertise the pair (NHi,rNHi) to all directly connected core routers. 5. The egress PE MAY advertise the pair (NHi,rNHi) to all core routers in the network. 6. The structure and method of advertising the pair (NHi,rNHi) is beyond the scope of this document. For example, the pair (NHi,rNHi) may be advertised through an ISIS optional TLV. 7. The semantics of the pair (NHi,rNHi) are: If the next-hop NHi becomes unreachable, then traffic destined to the next-hop NHi SHOULD be re-tunneled to the next-hop rNHi because rNHi can reach prefixes reachable via the primary next-hop NHi. 8. Because of the previous steps, core routers that are directly connected to the egress PE (and possibly other core routers) are aware of the repair next-hop for protected BGP prefixes reachable via the egress PE. Note that a core router is totally unaware of the BGP prefixes. 2.1.4. Step 4: How a P router (a core router) Programs its Forwarding Plane 1. Through usual IGP mechanism, the P router has a prefix matching every BGP next-hop. Let the next-hop NHi match the route Ri 2. The next-hop of prefix Ri is on the path towards the primary egress PE. 3. Thus the FIB entry for Ri is programmed as follows: a. Primary next-hop: the next router on the path towards NHi b. Repair next-hop: the next-router on the path towards rNHi 2.2. Control plane Operation for Labeled Prefixes This section specifies the operation of the control plane for AFI/SAFI 1/4, 2/4, 1/128, and 2/128. Bashandy Expires April 26, 2012 [Page 8] Internet-Draft BGP FRR using Repair Label October 2011 2.2.1. Step 1: Calculation of the Repair PE 1. As usual, each PE allocates a local label for each prefix it can reach through an external neighbor CE. A PE may also allocate a repair label is specified in [11]. 2. Each edge router advertises the prefix together with the local label and possibly the repair label [11] to some or all of its IBGP peers. 3. As a result, an edge router PEi having an external path to the prefix P/p may learn about the prefix through other IBGP peers. 4. The edge router PEi MAY choose a repair PE for the external prefix P/p. Rules for choosing the repair PE are specified in Section 2.3. 5. The edge router PEi chooses the one of labels advertised by the other edge router PEj for the prefix P/p as the "repair label". The algorithm for choosing the repair label is specified in Section 2.3. 6. In the end, if the edge router PEi can reach the prefix P/p through and external path and the prefix P/p is advertised by at least one other PE, the edge router PEi will have o a primary path towards the CE from which it learnt the prefix, and o a repair path consisting of a repair PE and a repair label advertised by the chosen repair PE. 2.2.2. Step 2: Assigning and Advertising the BGP Next-hop 1. The edge router PEi groups all BGP prefixes for which PEi has an external path and a repair path as follows: Two prefixes belong to the same group Gi if they share the same repair PE and repair label 2. The remaining steps are identical to the steps used by unlabeled prefixes in section 2.2.2. . 2.2.3. Step 3: Informing core routers about the repair path 1. In step 2 (Section 2.2.2. ) the egress PE assigns a primary next-hop NHi and a repair path (consisting of a repair next-hop and repair label) for protected prefixes belonging to group Gi. 2. The primary next-hop NHi is advertised into IGP as usual Bashandy Expires April 26, 2012 [Page 9] Internet-Draft BGP FRR using Repair Label October 2011 3. The repair next-hop is the next-hop advertised for the prefix P/p by the repair edge router PEj. Denote the repair next-hop for prefixes belonging to group Gi by "rNHi". Denote the repair label for prefixes belonging to group Gi by "rLi". Because rNHi is the next-hop attribute advertised by the repair PE, rNHi will also be known to all core routers via IGP 4. The repairing egress PE MUST advertise the triplet (NHi, rNHi, rLi) to all directly connected core routers. 5. The repairing egress PE MAY advertise the triplet (NHi, rNHi, rLi) to all core routers in the network 6. The triplet (NHi,rNHi, rLi) may be advertised through various means, such as ISIS optional TLV. The structure and method of advertising the triplet (NHi,rNHi,rLi) is beyond the scope of this document. 7. The semantics of the pair (NHi,rNHi,rLi) are: If the next-hop NHi becomes unreachable, then traffic destined to the next-hop NHi should be re-tunneled to the next-hop rNHi and the label pushed by the ingress PE MUST be swapped with the label rLi 8. Because of the previous steps, core routers that are directly connected to the egress edge router (and possibly other core routers) are aware of the repair path for protected BGP prefixes reachable via the egress edge router. Note that a core router is totally unaware of the BGP prefixes themselves 2.2.4. Step 4: How a P router (a core router) programs its forwarding plane 1. Through usual IGP mechanism, the P router has a prefix matching every BGP next-hop. Let the primary next-hop NHi match the route Ri 2. The next-hop of prefix Ri is on the path towards the protected egress edge router PEi. The next-hop of the prefix Ri is considered the primary path for the prefix Ri 3. Thus the FIB entry for Ri is programmed as follows a. Primary path: the next router on the path towards NHi b. Repair path: i. Pop label in the packet right under the tunnel header (irrespective of the value of that label) Bashandy Expires April 26, 2012 [Page 10] Internet-Draft BGP FRR using Repair Label October 2011 ii. Push the repair label rLi iii. Re-tunnel the packet towards the repair next-hop rNHi 2.3. Rules for a choosing Repair path This section specifies rules governing how an egress edge router PEi chooses the repair path. Other than the rules in this section, the method of choosing the repair path is beyond the scope of this document. 2.3.1. General Rules for Choosing and Programming the Repair Path This section specifies general rules for choosing the repair path for both labeled and unlabeled prefixes. 1. A repair PE MUST be another edge router PEj that advertises the same prefix to the edge router PEi via IBGP peering. 2. If the repairing "P" router determines that the path taken by the tunnel from the repairing "P" router to repair edge router PEj passes through the protected edge router PEi, then the repairing router "P" SHOULD NOT install the repair path in its forwarding plane. Instead the repair path MAY use a different FRR protection mechanism such as that specified in [8], [9], and [10]. The reason for this rule is that the tunnel to the repair edge router PEj does not provide protection against the failure of the edge node PEi. Instead it provides core protection against the failure of the path through the core leading to the protected edge node PEi. Thus existing core FRR protection mechanisms such as those specified in [8], [9], and [10] can be used 2.3.2. Rules for Choosing the Repair Path for Labeled Prefixes This section specifies additional rules by which an egress edge router PEi chooses the repair path for an external labeled prefix P/p. 1. A primary edge router PEi SHOULD only choose the edge router PEj and the repair label rLi as a repair path for the prefix P/p if label advertised for the prefix P/p by the repair edge router PEj is allocated on per-VPN or per-CE/per-next-hop basis. Bashandy Expires April 26, 2012 [Page 11] Internet-Draft BGP FRR using Repair Label October 2011 The reason for this is as follows. As mentioned in the abstract and Introduction, the core of the network SHOULD remain BGP-free and the size of the routing table on a core router SHOULD remain independent of the number of BGP prefixes. BGP prefix grouping in section 2.2.2. requires two prefixes to belong to two different groups if the labels advertised by the repair PE for the two prefixes are different. Thus if the repair edge router allocates labels on per-prefix basis, protected edge router PEi will advertise a different primary next-hop for each protected prefix. This is equivalent to having core router "P" knowing about every BGP prefix. In addition the size of the routing table of the "P" router becomes comparable to the number of BGP prefixes. 2. If the repair edge router PEj advertises a repair label as described in [11], then the protected edge router PEi MAY choose the repair label advertised by PEj as the repair label for the prefix P/p. Using the repair label specified in [11] has two advantages: o A repairing edge router PEj need not change the primary label allocation policy (which may be per-prefix) but can be chosen as repair PE if the repair labels are allocated on per-CE or per-VRF basis. o As mentioned in [11], an edge router does NOT repair a packet arriving with a repair label. Hence using the repair label when re-tunneling the packet towards PEj guarantees loop freedom in case of PE-CE link failure. 2.4. Forwarding Plane Operation This section specifies the forwarding plane operation on the core router "P" when it detects that the protected edge router PEi is no longer reachable. We assume that the core router has pre-programmed its forwarding plane according to Sections 2.1. and 2.2. . 2.4.1. For unlabeled prefix The forwarding table for the route Ri is programmed according to section 2.1.4. . As soon as the "P" router detects that the primary next-hop for Ri is not reachable it does the following for any packet destined to the protected edge router PEi. 1. Decapsulate tunnel header of the arriving packet 2. Tunnel the packet towards the repair egress PE identified by the repair next-hop rNHj Bashandy Expires April 26, 2012 [Page 12] Internet-Draft BGP FRR using Repair Label October 2011 2.4.2. For Labeled prefix The forwarding table for the route Ri is programmed according to section 2.2. . Remember that packets tunneled to the egress edge PEi have a label under the tunnel encapsulation. As soon as the "P" router detects that the primary next-hop for Ri is not reachable it does the following for any arriving labeled packet destined to the protected edge router PEi 1. Decapsulate the tunnel header to expose the labeled packet 2. Swap the label on the top of the packet (irrespective of the value of that label) with the repair label rLi 3. Tunnel the packet towards the repair egress PE identified by rNHj Bashandy Expires April 26, 2012 [Page 13] Internet-Draft BGP FRR using Repair Label October 2011 3. Example We will use and LDP core as an example. Consider the diagram depicted in Figure 2 below. We assume that the PEs advertise repair labels as specified in [11] +-----------------------------------+ | | | LDP Core | | | | PE1 | |\ | | \ | | \ | | \ | | CE1....... VPN prefix | | / (10.0.0.0/8) | | / (11.0.0.0/8) | | / | |/ PEx P--------PE0 Lo1 = 1.1.1.1/32 | |\ Lo2 = 2.2.2.2/32 | | \ | | \ | | \ | | CE2....... VPN prefix | | / (20.0.0.0/8) | | / (21.0.0.0/8) | | / | |/ | PE2 | | | | +-----------------------------------+ Figure 2 : Edge node BGP FRR in LDP core 1. As we can see, PE0 has 4 prefixes: 10.0.0.0/8, 11.0.0.0/8, 20.0.0.0/8, and 21.0.0.0/8. PE0 may assign a separate label to each prefix. The method and policy of assigning primary labels to each prefixes is irrelevant to this document. 2. PE1 advertises the repair label rL1 for prefixes 10.0.0.0/8 and 11.0.0.0/8 3. PE2 advertises the repair label rL2 for prefixes 20.0.0.0/8 and 21.0.0.0/8 Bashandy Expires April 26, 2012 [Page 14] Internet-Draft BGP FRR using Repair Label October 2011 4. As such, PE0 divides its prefixes into two groups G1 = {10.0.0.0/8, 11.0.0.0/8} G2 = {20.0.0.0/8, 21.0.0.0/8} 5. When advertising the next-hop to its IBGP peer, PE0 advertises 1.1.1.1 as the next-hop for prefixes belonging to group G1 and 2.2.2.2 as the next-hop for prefixes belonging to group G2. 6. PE0 advertises the prefixes 1.1.1.1/32 and 2.2.2.2/32 using the usual IGP mechanism. 7. When advertising 1.1.1.1/32 into the core, PE0 advertises rL1 and PE1 as a repair path. When advertising 2.2.2.2/32 into the core, PE0 advertises rL2 and PE2 as a repair path. The mechanism by which a repair path is advertised is beyond the scope of the proposal. 8. On the penultimate hop router "P", LDP assigns a different LDP label to 1.1.1.1/32 and 2.2.2.2/32. Core routers other than penultimate hop routers may employ some sort of label aggregation to reduce the number of LDP labels 9. Assume that the penultimate hop router "P" assigns the local LDP label L1 for prefix 1.1.1.1/32 and L2 for prefix 2.2.2.2/32 10.On the penultimate router P, the forwarding entry for L1 will be as follows Primary path: - nexthop is PE0. - swap the incoming outer label with the LDP label towards 1.1.1.1 Repair path - Pop the incoming LDP label - Swap the internal label with the repair label rL1 - Push the LDP label towards PE1 - Forward the packet 11.On the core router P, the forwarding entry for L2 will be as follows Primary path: Same as L1 Repair Path - Pop the incoming LDP label - Swap the internal label with the repair label rL2 - Push the LDP label towards PE2 - Forward the packet Bashandy Expires April 26, 2012 [Page 15] Internet-Draft BGP FRR using Repair Label October 2011 12.If the P router detects that PE0 is no longer reachable, it can use the repair path already pre-programmed in the forwarding plane as described above. Because the repair path is pre- programmed as in the case of TE and IP FRR, the P router can re- route traffic very fast 4. Security Considerations No additional security risk is introduced by using the mechanisms proposed in this document 5. IANA Considerations No requirements for IANA 6. Conclusions This document proposes a method that allows fast re-route protection against edge node failure or complete disconnected from the core in a BGP-free core 7. References 7.1. Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [2] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway Protocol 4 (BGP-4), RFC 4271, January 2006 [3] Bates, T., Chandra, R., Katz, D., and Rekhter Y., "Multiprotocol Extensions for BGP", RFC 4760, January 2007 7.2. Informative References [4] Marques,P., Fernando, R., Chen, E, Mohapatra, P., Gredler, H., "Advertisement of the best external route in BGP", draft-ietf- idr-best-external-04.txt, April 2011. [5] Wu, J., Cui, Y., Metz, C., and E. Rosen, "Softwire Mesh Framework", RFC 5565, June 2009. [6] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private Networks (VPNs)", RFC 4364, February 2006. [7] De Clercq, J. , Ooms, D., Prevost, S., Le Faucheur, F., Connecting IPv6 Islands over IPv4 MPLS Using IPv6 Provider Edge Routers (6PE)", RFC 4798, February 2007 Bashandy Expires April 26, 2012 [Page 16] Internet-Draft BGP FRR using Repair Label October 2011 [8] Atlas, A. and A. Zinin, "Basic Specification for IP Fast Reroute: Loop-Free Alternates", RFC 5286, September 2008. [9] Shand, S., and Bryant, S., "IP Fast Reroute", RFC5714, January 2010 [10] Shand, M. and S. Bryant, "A Framework for Loop-Free Convergence", RFC 5715, January 2010. [11] Bashandy, A., Pithawala, P., and Heitz, J., "Scalable, Loop- Free BGP FRR using Repair Label, "draft-bashandy-idr-bgp- repair-label-02.txt", July 2011 8. Acknowledgments Special thanks to Keyur Patel for the valuable comments This document was prepared using 2-Word-v2.0.template.dot. Authors' Addresses Ahmed Bashandy Cisco Systems 170 West Tasman Dr, San Jose, CA 95134 Email: bashandy@cisco.com Bashandy Expires April 26, 2012 [Page 17]