Internet Engineering Task Force Y. Shen, Ed. Internet-Draft Juniper Networks Intended status: Standards Track R. Aggarwal Expires: December 27, 2012 Arktan, Inc W. Henderickx Alcatel-Lucent June 25, 2012 PW Endpoint Fast Failure Protection draft-shen-pwe3-endpoint-fast-protection-02 Abstract This document specifies a fast protection mechanism for pseudowires (PWs) against egress attachment circuit failure, egress PE failure (including multi-segment PW terminating PE failure), and multi- segment PW switching PE failure. Designed on the basis of multi- homed CE, PW redundancy, upstream label assignment and context specific label switching, the mechanism enables local repair to be performed by a router adjacent to a failure. In particular, the router can restore PW traffic in the order of tens of milliseconds, by transmitting the traffic to a protector through a pre-established bypass tunnel. Therefore, the mechanism is usable to reduce the packet loss that may happen before any global repair mechanism reacts to the failure or routers converge on the topology changes due to the failure. 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 December 27, 2012. Copyright Notice Copyright (c) 2012 IETF Trust and the persons identified as the Shen, et al. Expires December 27, 2012 [Page 1] Internet-Draft PW Endpoint Fast Failure Protection June 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 . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Specification of Requirements . . . . . . . . . . . . . . . . 4 3. Reference Models and Failure Cases . . . . . . . . . . . . . . 4 3.1. Single-Segment PW . . . . . . . . . . . . . . . . . . . . 5 3.2. Multi-Segment PW . . . . . . . . . . . . . . . . . . . . . 7 4. Theory of Operation . . . . . . . . . . . . . . . . . . . . . 8 4.1. Local Repair and Protector . . . . . . . . . . . . . . . . 8 4.2. Context Identifier . . . . . . . . . . . . . . . . . . . . 11 4.2.1. Uses of Context Identifier . . . . . . . . . . . . . . 11 4.2.2. Advertisement and Path Computation . . . . . . . . . . 12 4.3. Protection Models . . . . . . . . . . . . . . . . . . . . 14 4.4. Transport Tunnel . . . . . . . . . . . . . . . . . . . . . 17 4.5. Bypass Tunnel . . . . . . . . . . . . . . . . . . . . . . 18 4.6. PW Forwarding State on Protector . . . . . . . . . . . . . 18 4.6.1. Co-located Protector . . . . . . . . . . . . . . . . . 19 4.6.2. Centralized Protector . . . . . . . . . . . . . . . . 20 4.7. PW Label Distribution from Primary PE to Protector . . . . 22 4.7.1. Protection FEC Element Encoding for PWid . . . . . . . 24 4.7.2. Protection FEC Element Encoding for Generalized PWid . . . . . . . . . . . . . . . . . . . . . . . . . 25 4.8. PW Label Distribution from Backup PE to Protector . . . . 26 4.9. Revertive Behavior . . . . . . . . . . . . . . . . . . . . 27 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 28 6. Security Considerations . . . . . . . . . . . . . . . . . . . 28 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 28 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 28 8.1. Normative References . . . . . . . . . . . . . . . . . . . 28 8.2. Informative References . . . . . . . . . . . . . . . . . . 30 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 30 Shen, et al. Expires December 27, 2012 [Page 2] Internet-Draft PW Endpoint Fast Failure Protection June 2012 1. Introduction Per RFC 3985, RFC 4447 and RFC 5659, a pseudowire (PW) or PW segment can be thought of as a connection between a pair of forwarders hosted by two PEs, carrying an emulated layer-2 service over a packet switched network (PSN). In the single-segment PW (SS-PW) case, a forwarder binds a PW to an attachment circuit (AC). In the multi- segment PW (MS-PW) case, a forwarder on a terminating PE (T-PE) binds a PW segment to an AC, while a forwarder on a switching PE (S-PE) binds one PW segment to another PW segment. In each direction between the PEs, PW packets are transported by a PSN tunnel, which is called a transport tunnel. In order to protect a layer-2 service against network failures, it is necessary to protect every link and node along the entire data path, including ingress AC, ingress (T-)PE, intermediate routers of transport tunnel, S-PEs, egress (T-)PE, and egress AC. To minimize service disruption, it is also desirable that each of these components is protected by a fast protection mechanism based on local repair. Such a mechanism generally involves a bypass path that is pre-computed and pre-installed on a router adjacent to a failure. The bypass path has the property that it can guide traffic around the failure, while remaining unaffected by the topology changes resulting from the failure. When the failure happens, the router can invoke the bypass path to redirect the traffic, achieving fast restoration for the service. Today, fast protection against ingress AC failure and ingress (T-)PE failure is achievable by using a multi-homed CE and redundant PWs, where the CE can detect the failures and move traffic onto a backup ingress AC. Fast protection against failure of intermediate routers is achievable through RSVP fast-reroute (RFC 4090) and IP fast- reroute (RFC 5714 and RFC 5286). However, there is a lack of such protection against egress AC failure, egress (T-)PE failure, and S-PE failure. In these cases, service restoration has to rely on a global repair or control plane repair. Global repair is normally driven by ingress CE or ingress (T-)PE, and dependent on end-to-end OAM. Control plane repair is dependent on protocol convergence. Therefore, both mechanisms are relatively slow in reacting to failures and restoring traffic. This document specifies a fast protection mechanism for PWs based on local repair technique. It can protect PWs against the following types of failures. a. Egress AC failure. Shen, et al. Expires December 27, 2012 [Page 3] Internet-Draft PW Endpoint Fast Failure Protection June 2012 b. Egress PE failure: Node failure of egress PE of a SS-PW; Node failure of T-PE of an MS-PW. c. Switching PE failure: Node failure of S-PE of an MS-PW. The mechanism is relevant to networks with redundant PWs and multi- homed CEs. It is designed on the basis of MPLS upstream label assignment and context specific label switching (RFC 5331). Fast protection refers to the ability to restore traffic upon a failure in the order of tens of milliseconds. This is achieved by establishing local protection at the router adjacent to the failure. Compared with the existing global repair and control plane repair mechanisms, this mechanism can provide faster restoration. However, it is intended to complement those mechanisms, rather than replacing them in any way. The mechanism is applicable to LDP signaled PWs. 2. Specification of Requirements 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. 3. Reference Models and Failure Cases This document refers to the following topologies to describe PW endpoint failures and protection procedures. These topologies are commonly seen in an environment with multi-homed CEs and redundant PWs for global repair. In this document the fast protection mechanism also use them for the local repair purposes. This SHALL enable local repair and global repair to work in tandem to achieve broader scope of protection with better performance. Shen, et al. Expires December 27, 2012 [Page 4] Internet-Draft PW Endpoint Fast Failure Protection June 2012 3.1. Single-Segment PW |<-------------- PW1 --------------->| - PE1 -------------- P1 ---------------- PE2 - / \ / \ CE1 CE2 \ / \ / - PE3 -------------- P2 ---------------- PE4 - |<-------------- PW2 --------------->| Figure 1 In Figure 1, the IP/MPLS network consists of PE-routers and P-routers. It provides an emulation of a layer-2 service between CE1 and CE2. Each CE is multi-homed to two PEs. Hence, there are two divergent paths between the CEs. The first path uses PW1 established between PE1 and PE2, connecting the AC CE1-PE1 and the AC CE2-PE2. The second path uses PW2 established between PE3 and PE4, connecting the AC CE1-PE3 and the AC CE2-PE4. The operational states of all the PWs and ACs are up. The transport tunnels of the PWs are not shown in this figure for clarity. At any given time, each CE sends traffic via only one AC and receives traffic via only one AC. The two ACs MAY or MAY NOT be the same. The AC used to send traffic is determined by the CE, and MAY rely on an end-to-end OAM mechanism between the CEs. The AC used for the CE to receive traffic is determined by the state of the network and the protection mechanism in use, as described later in this document. From the perspective of traffic towards a given CE, the set of PWs, PEs and ACs involved can be viewed to serve primary and backup (or active and standby) roles. When the network is in a steady state, the PW that is intended to carry the traffic is referred to as a primary PW. The PE at the egress of the primary PW is a primary PE. The AC connecting the CE and the primary PE is a primary AC. The other PW that may be used to carry the traffic upon a network failure are referred to as a backup PW. The PE at the egress of the backup PW is a backup PE. The AC connecting the CE and the backup PE is a backup AC. In this document, the following primary and backup roles are assigned Shen, et al. Expires December 27, 2012 [Page 5] Internet-Draft PW Endpoint Fast Failure Protection June 2012 for the traffic going from CE1 to CE2: Primary PW: PW1 Primary PE: PE2 Primary AC: CE2-PE2 Backup PW: PW2 Backup PE: PE4 Backup AC: CE2-PE4 In this case, an egress AC failure refers to the failure of the primary AC, i.e. the AC CE2-PE2. An egress node failure refers to the failure of the primary PE, i.e. PE2. The backup PE, backup PW and backup AC may be used to carry the traffic when CE1 and CE2 switches traffic to PW2 during a global repair, or when a local repair takes effect, as described later in this document. |<-------------- PW1 --------------->| ------------- P1 ---------------- PE2 - / \ / \ CE1 -- PE1 CE2 \ / \ / ------------- P2 ---------------- PE4 - |<-------------- PW2 --------------->| Figure 2 Figure 2 shows another possible scenario, where CE1 is single-homed to PE1, while CE2 remains multi-homed to PE2 and PE4. From the perspective of egress protection for the traffic from CE1 to CE2, this topology is not much different than Figure 1. However, for the traffic in the opposite direction, i.e. from CE2 to CE1, PE1 must anticipate the traffic on PW1 and PW2, and sends it to CE1 over the AC CE1-PE1 in both cases. Shen, et al. Expires December 27, 2012 [Page 6] Internet-Draft PW Endpoint Fast Failure Protection June 2012 3.2. Multi-Segment PW |<--------------- PW1 --------------->| |<----- SEG1 ----->|<----- SEG2 ----->| - TPE1 -------------- SPE1 --------------- TPE2 - / \ / \ CE1 CE2 \ / \ / - TPE3 -------------- SPE2 --------------- TPE4 - |<----- SEG3 ----->|<----- SEG4 ----->| |<--------------- PW2 --------------->| Figure 3 Figure 3 shows a topology that is similar to Figure 1 but in an MS-PW environment. PW1 and PW2 are both MS-PWs. PW1 is established between TPE1 and TPE2, and switched between segments SEG1 and SEG2 at SPE1. PW2 is established between TPE3 and TPE4, and switched between segments SEG3 and SEG4 at SPE2. CE1 is multi-homed to TPE1 and TPE3. CE2 is multi-homed to TPE2 and TPE4. The transport tunnels of the PW segments are not shown in this figure for clarity. In this document, the following primary and backup roles are assigned for the traffic going from CE1 to CE2: Primary PW: PW1 Primary T-PE: TPE2 Primary S-PE: SPE1 Primary AC: CE2-TPE2 Backup PW: PW2 Backup T-PE: TPE4 Backup S-PE: SPE2 Backup AC: CE2-TPE4 In this case, an egress AC failure refers to the failure of the primary AC, i.e. the AC CE2-TPE2. An egress node failure refers to Shen, et al. Expires December 27, 2012 [Page 7] Internet-Draft PW Endpoint Fast Failure Protection June 2012 the failure of the primary T-PE, i.e. TPE2. In addition, an switching node failure refers to the failure of the primary S-PE, i.e. SPE1. The backup T-PE, backup PW and backup AC are used for protecting the primary PW against egress AC failure and egress node failure. The backup S-PE and the backup PW are used for protecting the primary PW against switching node failure, as described later in this document. For consistency with the SS-PW scenario, primary T-PEs and a primary S-PEs may simply be referred to as primary PEs in this document, where specifics is not required. Similarly, backup T-PEs and backup S-PEs may be referred to as backup PEs. 4. Theory of Operation The fast protection mechanism in this document provides three types of protection for PWs, corresponding to the three types of failures described in Section 1. a. Egress AC protection b. Egress (T-)PE node protection c. S-PE node protection The mechanism is only relevant when the target CE is multi-homed to a primary PE and a backup PE, and when there is a backup PW in the network. In S-PE node protection, it is also assumed that there is a backup S-PE on the backup PW. 4.1. Local Repair and Protector The mechanism relies on local repair to be performed by routers adjacent to failures. Each of these routers is referred to as a "point of local repair" (PLR). A PLR MUST be able to detect a failure by using a rapid mechanism, such as physical layer failure detection, Bidirectional Failure Detection (BFD) (RFC 5880), etc. In anticipation of the failure, the PLR MUST also pre-establish a bypass PSN tunnel to a "protector", and pre-install a bypass route in the FIB (forwarding information base). The bypass tunnel has the property that it is not affected by the topology changes caused by the failure. Upon detecting the failure, the PLR MUST invoke the bypass route and forward traffic to the protector through the bypass tunnel. The protector MUST in turn forward the traffic towards the target CE, which may or may not be directly attached to the protector. This procedure is referred to as local repair. Shen, et al. Expires December 27, 2012 [Page 8] Internet-Draft PW Endpoint Fast Failure Protection June 2012 Different routers may serve as PLRs and protectors in different scenarios. o In egress AC protection, the PLR is the primary PE that hosts the primary AC, and the protector is the backup PE (Figure 4). |<-------------- PW1 --------------->| - PE1 -------------- P1 ---------------- PE2 - / PLR \ / | \ CE1 bypass| CE2 \ | / \ | / - PE3 -------------- P2 ---------------- PE4 - protector |<-------------- PW2 --------------->| Figure 4 o In egress PE node protection, the PLR is the penultimate hop router of transport tunnel of primary PW, and the protector is the backup PE (Figure 5). |<-------------- PW1 --------------->| - PE1 -------------- P1 ------- P3 ----- PE2 - / PLR \ \ / \ \ CE1 bypass\ CE2 \ \ / \ \ / - PE3 -------------- P2 ---------------- PE4 - protector |<-------------- PW2 --------------->| Figure 5 o In S-PE node protection, the PLR is the penultimate hop router of transport tunnel of primary PW segment, and the protector is the backup S-PE (Figure 6). Shen, et al. Expires December 27, 2012 [Page 9] Internet-Draft PW Endpoint Fast Failure Protection June 2012 |<--------------- PW1 --------------->| |<----- SEG1 ----->|<----- SEG2 ----->| - TPE1 ----- P4 ----- SPE1 -------------- TPE2 - / PLR \ \ / \ \ CE1 bypass\ CE2 \ \ / \ \ / - TPE3 --------------- SPE2 -------------- TPE4 - protector |<----- SEG3 ----->|<----- SEG4 ----->| |<--------------- PW2 --------------->| Figure 6 When a PLR forwards traffic through a bypass tunnel to a protector, it MUST keep the original PW label intact. In particular, it SHOULD NOT forward the traffic based on the PW label or modify the PW label. Such forwarding state on the PLR has the advantages that it represents simple forwarding operations and it is easy to set up. The PLR does not need to learn PW labels or install bypass routes on a per PW label basis. This also means that the protector MUST forward the traffic based on a PW label that is assigned by the primary PE, and ensure that the traffic can eventually reach the target CE. From the protector's perspective, this PW label is an upstream assigned label (RFC 5331). This is accomplished by learning the PW label from the primary PE, installing the proper forwarding state for the PW label in the label space associated with the primary PE, and performing PW label lookup in this label space. A protector MAY be a backup (S-)PE as illustrated in the above examples, or a dedicated router that assumes such a role. In the later case, the protector is not necessarily the backup (S-)PE of a given primary PW. During a local repair, the PLR still forwards traffic to the protector through a bypass tunnel, and the protector MUST then forward the traffic to the backup (S-)PE, which finally forwards the traffic to the target CE via a backup AC or a backup PW segment. More detail will be provided in Section 4.3. A protector MAY protect primary PWs for one or multiple primary PEs. The protector MUST maintain a separate label space for each primary PE. Likewise, the primary PWs hosted by a primary PE MAY be protected by multiple protectors, each for a subset of the PWs. In any case, a primary PW is associated with one and only one pair of Shen, et al. Expires December 27, 2012 [Page 10] Internet-Draft PW Endpoint Fast Failure Protection June 2012 {primary PE, protector}. 4.2. Context Identifier An IPv4/v6 address is assigned to each ordered pair of {primary PE, protector} to facilitate protection establishment. This address is referred to as a "context identifier". It MUST be globally unique, or unique within the address space of the network where the primary PE and the protector reside. 4.2.1. Uses of Context Identifier A context identifier serves two purposes. o It identifies a primary PE and an associated protector. In other words, it identifies a primary PE on a per protector basis. A given primary PE may be protected by multiple protectors, each for a subset of the primary PWs hosted by the primary PE. Therefore, a distinct context identifier MUST be assigned to the primary PE for each protector. For a primary PW, its transport tunnel MUST be destined for the context identifier of its {primary PE, protector}, rather than an IP address of the primary PE. This not only enables the transport tunnel to follow a path to the primary PE, but also indicates the protector to the PLR(s). o It indicates the primary PE's label space to a protector. The protector may protect primary PWs for multiple primary PEs. It MUST maintain a separate label space for each primary PE. PW labels assigned by a given primary PE MUST be associated with the label space indicated by the context identifier of the {primary PE, protector}. The association is accomplished as below. When the primary PE advertises the label of a primary PW to the protector, it MUST attach the information of the context identifier (Section 4.7). Upon receiving the advertisement, the protector MUST install the PW label in the label space corresponding to the context identifier. A bypass tunnel MUST be destined for the context identifier, rather than an IP address of the protector. Therefore, the bypass tunnel (either MPLS tunnel label or IP tunnel destination address) is equivalent to the context identifier. All packets received on the bypass tunnel MUST be forwarded in the label space indicated by the bypass tunnel. Shen, et al. Expires December 27, 2012 [Page 11] Internet-Draft PW Endpoint Fast Failure Protection June 2012 4.2.2. Advertisement and Path Computation Using a context identifier as destination for both transport and bypass tunnels imposes the following requirements on path computation for these tunnels. o On the ingress PE, path computation for a transport tunnel MUST choose the primary PE as the endpoint. o On a PLR, path computation for a bypass tunnel MUST avoid the primary PE and choose the protector as the endpoint. The path MUST NOT traverse the primary PE. In order to satisfy these requirements, a context identifier SHOULD be advertised by IGP and/or IGP-TE in the routing domain and/or the TE domain, depending on the tunnel technologies of the network. o If RSVP-TE is used to establish both transport and bypass tunnels, the context identifier MUST be advertised by IGP-TE. o If IP or LDP is used to establish both transport and bypass tunnels, the context identifier MUST be advertised by IGP. o If IP or LDP is used for transport tunnels while RSVP-TE is used for bypass tunnels, or vice versa, the context identifier MUST be advertised by both IGP and IGP-TE. In any case, it is recommended that the context identifier SHOULD be advertised as a proxy node that is dual-attached to the primary PE and the protector via unnumbered point-to-point interfaces, as shown in Figure 7. This schema ensures that the CSPF (constrained shortest path first), LFA (loop free alternate; RFC 5286) and MRT (maximally redundant trees; [IP-LDP-FRR-MRT]) algorithms can compute the expected paths for the transport tunnel and bypass tunnel, whether the tunnels are MPLS tunnels or IP tunnels. Shen, et al. Expires December 27, 2012 [Page 12] Internet-Draft PW Endpoint Fast Failure Protection June 2012 primary PE - \ metric 1, TE metric 1, bandwidth max \ \ \ \ metric max, TE metric max, bandwidth 0 | proxy node | / metric max, TE metric max, bandwidth 0 / / / / metric X, TE metric Y, bandwidth max protector - Figure 7 o The primary PE advertises an unnumbered link to the proxy node, with metric 1, TE metric 1, and maximum bandwidth. o The protector advertises an unnumbered link to the proxy node, with metric X, TE metric Y, and maximum bandwidth. X SHOULD be carefully chosen so that the path from any given source node (ingress PE or PLR) via the protector to the proxy node will have a higher metric than the corresponding path from the source node via the primary PE to the proxy node. The same requirement applies to Y as well for TE paths. o The primary PE advertises the proxy node with two unnumbered links to the primary PE and the protector, respectively. The router ID of the proxy node is the context identifier. Both unnumbered links are advertised with maximum metric, maximum TE metric, and zero bandwidth. This ensures that the proxy node does not serve as a transit node for any paths. In the case of ISIS [ISO10589], the system ID is derived from the context identifier with Binary Coded Decimal (BCD) encoding. The resulting system-ID MUST be unique. The LSP (Link State Packet) MUST include an Area Address TLV, and MAY include a Dynamic Hostname TLV. The area addresses MUST be a subset of or preferably identical to those advertised by the primary PE at the corresponding level. The hostname MAY be derived from the context identifier and the primary PE's hostname. The Overload bit MUST be set to 1. The Attached and the Partition Repair bits MUST be set to 0. In the case of OSPF (RFC 2328), the Advertising Router and Link Shen, et al. Expires December 27, 2012 [Page 13] Internet-Draft PW Endpoint Fast Failure Protection June 2012 State ID of the router LSA (Link State Advertisement) MUST both be the context identifier. All options bits in the router LSA MUST be set to zero. With this schema, the proxy node is reachable via both the primary PE and the protector in the routing domain and the TE domain. For any given ingress PE or PLR, the path via the primary PE to the proxy node is considered to have a higher preference than the path via the protector, due to the lower metric. Therefore, in path computation for a transport tunnel, a path via the primary PE SHOULD always be selected. However, in path computation for a bypass tunnel, where the primary PE must be avoided, a path via the protector SHOULD be selected. 4.3. Protection Models There are two protection models based on the location and role of a protector. A network MAY use either protection model, or a combination of both. 1. Co-located protector In this model, the protector is a backup PE that is directly connected to the target CE via a backup AC, or it is a backup S-PE on a backup PW. That is, the protector is co-located with the backup (S-)PE. Examples of this model have been introduced in Figure 4, Figure 5 and Figure 6 in Section 4.1. In egress AC protection and egress PE node protection, when a protector receives traffic from the PLR, it forwards the traffic to the CE via the backup AC. This is shown in Figure 8, where PE2 is the PLR for egress AC failure, P3 is the PLR for PE2 failure, and PE4 (the backup PE) is the protector. Shen, et al. Expires December 27, 2012 [Page 14] Internet-Draft PW Endpoint Fast Failure Protection June 2012 |<-------------- PW1 --------------->| - PE1 -------------- P1 ------- P3 ----- PE2 ---- / PLR \ PLR \ / \ | \ CE1 bypass\ |bypass CE2 \ \ | / \ \ | / - PE3 -------------- P2 ---------------- PE4 ---- protector |<-------------- PW2 --------------->| Figure 8 In S-PE node protection, when a protector receives traffic from the PLR, it MUST forward the traffic via the next segment of the backup PW. The T-PE of the backup PW MUST forward the traffic to the CE via a backup AC. This is shown in Figure 9, where P4 is the PLR for SPE1 failure, and SPE2 (the backup S-PE) is the protector for SPE1 (the primary S-PE). |<--------------- PW1 --------------->| |<----- SEG1 ----->|<----- SEG2 ----->| - TPE1 ----- P4 ----- SPE1 -------------- TPE2 - / PLR \ \ / \ \ CE1 bypass\ CE2 \ \ / \ \ / - TPE3 --------------- SPE2 -------------- TPE4 - protector |<----- SEG3 ----->|<----- SEG4 ----->| |<--------------- PW2 --------------->| Figure 9 In the co-located protector model, the number of context identifiers required by a network is the number of distinct {primary PE, backup PE} pairs. Therefore, the model is suitable for scenarios where the number backup PEs for any given primary PE is relatively small. Shen, et al. Expires December 27, 2012 [Page 15] Internet-Draft PW Endpoint Fast Failure Protection June 2012 2. Centralized protector In this model, the protector is a dedicated P router or PE router that protects all the primary PWs for one or multiple primary PEs. In egress AC protection and egress PE node protection, the protector MAY or MAY NOT be a backup PE with a direct connection to the target CE. In S-PE node protection, it MAY or MAY NOT be a backup S-PE of the backup PW. In egress AC protection and egress PE node protection, when the protector receives traffic from the PLR, if the protector has a direct connection (i.e. backup AC) to the CE, it MUST forward the traffic to the CE via the backup AC, which is similar to Figure 8. Otherwise, it MUST forward the traffic to a backup PE, which MUST then forward the traffic to the CE via a backup AC. This is shown in Figure 10, where the protector receives traffic from P3 or PE2 (the PLRs) and forwards the traffic to PE4 (the backup PE). The protector may be protecting other PWs as well, which are not shown in this figure. |<------------- PW1 --------------->| - PE1 ------------- P1 ------- P3 ----- PE2 -- / PLR \ PLR \ / \ / \ / bypass\ /bypass \ / \ / \ CE1 protector CE2 \ \ / \ \ / \ \ / \ \ / - PE3 ------------- P2 -----------------PE4 -- |<------------- PW2 --------------->| Figure 10 In S-PE node protection, when the protector receives traffic from the PLR, if the protector is a backup S-PE of the backup PW, it MUST forward the traffic via the next segment of the backup PW, and the T-PE of the backup PW MUST forward the traffic to the CE via a backup AC, which is similar to Figure 9. Otherwise, the protector MUST first forward the traffic to the backup S-PE, which MUST then forward the traffic via the next segment of the backup PW. Finally, the T-PE of the backup PW MUST forward the Shen, et al. Expires December 27, 2012 [Page 16] Internet-Draft PW Endpoint Fast Failure Protection June 2012 traffic to the CE via a backup AC. This is shown in Figure 11, where the protector forwards traffic to SPE2 (the backup S-PE). The protector may be protecting other PW segments as well, which are not shown in this figure. |<--------------- PW1 --------------->| |<----- SEG1 ----->|<----- SEG2 ----->| - TPE1 ----- P4 ----- SPE1 -------------- TPE2 - / PLR \ \ / \ \ / bypass\ \ / \ \ CE1 protector CE2 \ \ / \ \ / \ \ / \ \ / - TPE3 --------------- SPE2 -------------- TPE4 - |<----- SEG3 ----->|<----- SEG4 ----->| |<--------------- PW2 --------------->| Figure 11 In the centralized protector model, each primary PE MAY only need one protector to protect all of its PWs. Therefore, the number of context identifiers required by a network can be as low as the number of primary PEs. 4.4. Transport Tunnel The ingress PE of a primary PW (or PW segment) associates the PW with the primary egress PE through LDP signaling. The ingress PE MUST also associate the transport tunnel of the PW with the context identifier of the {primary PE, protector} of the PW. In particular, the destination of the transport tunnel MUST be the context identifier (Section 4.2.1). This not only ensures PW traffic to be transported to the primary PE, but also facilitates bypass tunnel establishment for PLR(s), as the context identifier implies both the primary PE and the protector. The association between the transport tunnel and the context identifier MAY be achieved by configuration or an auto-discovery mechanism. In the later case, the ingress PE MAY learn the context identifier from the primary PE, if the primary PE advertises the Shen, et al. Expires December 27, 2012 [Page 17] Internet-Draft PW Endpoint Fast Failure Protection June 2012 context identifier as "third party next hop" in an IPv4/v6 Interface_ID TLV (RFC 3471, RFC 3472) in LDP Label Mapping message. 4.5. Bypass Tunnel A PLR may provide protection for multiple primary PWs associated with one or multiple pairs of {primary PE, protector}. The PLR MUST establish a bypass tunnel to each protector for each distinct context identifier associated with the protector. The destination of the bypass tunnel MUST be the context identifier, as described in Section 4.2.1. The association between the destination and the context identifier can be achieved by PLR learning or inheriting destination address from the transport tunnel. For examples, in Figure 8 and Figure 10, a bypass tunnel is established from PE2 (PLR for egress AC failure) to the protector, and another bypass tunnel is established from P3 (PLR for egress node failure) to the protector. In Figure 9 and Figure 11, a bypass tunnel is established from P4 (PLR for switching node failure) to the protector. During a local repair, the PLR forwards traffic to the protector through the bypass tunnel with PW label intact. This normally involves pushing an MPLS label to the label stack, if the bypass tunnel is an MPLS tunnel, or pushing an IP header to the packet, if the bypass tunnel is an IP tunnel. The protector MUST then forward the traffic based on this PW label, i.e. an upstream assigned label. In order to perform such forwarding, the protector MUST treat the bypass tunnel as a context to determine the primary PE's label space. Specifically, if the bypass tunnel is an MPLS tunnel, the protector MUST assign a non-reserved label for the bypass tunnel, and use this label as the context. If the bypass tunnel is an IP tunnel, the destination address in its IP header should be the context identifier. A bypass tunnel MUST have the property that it is not affected by the topology changes caused by the failure that the bypass tunnel protects against. Therefore, it can be used to transmit traffic during the convergence period of routing protocols and the delay of global repair. It will remain effective, until the current transport tunnel is rerouted around the failure, or the traffic is moved to another PW or transport tunnel. 4.6. PW Forwarding State on Protector A protector MUST be able to forward traffic based on the PW label assigned by a primary PE. Therefore, it MUST learn the PW labels from all the primary PEs that it protects (Section 4.7), and maintain Shen, et al. Expires December 27, 2012 [Page 18] Internet-Draft PW Endpoint Fast Failure Protection June 2012 the PW labels in separate label spaces for the primary PEs. In the control plane, a primary PE's label space is identified by the context identifier of the {primary PE, protector}. When the protector learns a PW label from the primary PE, it MUST associate the PW label with the label space via this context identifier. In the forwarding plane, the label space is indicated by bypass tunnels that are destined for the context identifier. 4.6.1. Co-located Protector In Figure 12, PE4 is a co-located protector that protects PW1 against egress AC failure and egress node failure. It maintains a label space for PE2, which is identified by the context identifier of {PE2, PE4}. It learns from PE2 the label that PE2 has assigned to PW1, and installs an forwarding entry for the label in the label space. The nexthop of the forwarding entry indicates a label pop with outgoing interface pointing to the backup AC CE2-PE4. |<-------------- PW1 --------------->| - PE1 -------------- P1 ------- P3 ----- PE2 ---- / PLR \ PLR \ / \ | \ CE1 bypass\ |bypass CE2 \ \ | / \ \ | / - PE3 -------------- P2 ---------------- PE4 ---- protector |<-------------- PW2 --------------->| Figure 12 In Figure 13, SPE2 is a co-located protector that protects PW1 against switching node failure. It maintains a label space for SPE1, which is identified by the context identifier of {SPE1, SPE2}. It learns the label that SPE1 has assigned to the PW segment SEG1, and installs a forwarding entry in the label space. The nexthop of the forwarding entry indicates a label swap to the label of the PW segment SEG4. Shen, et al. Expires December 27, 2012 [Page 19] Internet-Draft PW Endpoint Fast Failure Protection June 2012 |<--------------- PW1 --------------->| |<----- SEG1 ----->|<----- SEG2 ----->| - TPE1 ----- P4 ----- SPE1 --------------- TPE2 - / PLR \ \ / \ \ CE1 bypass\ CE2 \ \ / \ \ / - TPE3 --------------- SPE2 --------------- TPE4 - protector |<----- SEG3 ----->|<----- SEG4 ----->| |<--------------- PW2 --------------->| Figure 13 4.6.2. Centralized Protector In the centralized protector model, for each primary PW of which the protector is not a backup (S-)PE, the protector MUST also learn the label of the backup PW from the backup (S-)PE (Section 4.8). This is the backup (S-)PE that the protector will forward traffic to. The protector MUST use the label as the outgoing label for the forwarding entry of the primary PW label. In Figure 14, the protector is a centralized protector that protects PW1 against egress AC failure and egress node failure. It maintains a label space for PE2, which is identified by the context identifier of {PE2, protector}. It learns from PE2 the label that PE2 has assigned to PW1, and learns from PE4 the label that PE4 has assigned to PW2. It installs a forwarding entry for PW1's label in the label space. The nexthop of the forwarding entry indicates a label swap to PW2's label. Shen, et al. Expires December 27, 2012 [Page 20] Internet-Draft PW Endpoint Fast Failure Protection June 2012 |<------------- PW1 --------------->| - PE1 ------------- P1 ------- P3 ----- PE2 -- / PLR \ PLR \ / \ / \ / bypass\ /bypass \ / \ / \ CE1 protector CE2 \ \ / \ \ / \ \ / \ \ / - PE3 ------------- P2 -----------------PE4 -- |<------------- PW2 --------------->| Figure 14 In Figure 15, the protector is a centralized protector that protects the PW segment SEG1 of PW1 against switching node failure of SPE1. It maintains a label space for SPE1, which is identified by the context identifier of {SPE1, protector}. It learns from SPE1 the label that SPE1 has assigned to SEG1, and learns from SPE2 the label that SPE2 has assigned to SEG3. It installs a forwarding entry for SEG1's label in the label space. The nexthop of the forwarding entry indicates a label swap to SEG3's label. Shen, et al. Expires December 27, 2012 [Page 21] Internet-Draft PW Endpoint Fast Failure Protection June 2012 |<--------------- PW1 --------------->| |<----- SEG1 ----->|<----- SEG2 ----->| - TPE1 ----- P4 ----- SPE1 -------------- TPE2 - / PLR \ \ / \ \ / bypass\ \ / \ \ CE1 protector CE2 \ \ / \ \ / \ \ / \ \ / - TPE3 --------------- SPE2 -------------- TPE4 - |<----- SEG3 ----->|<----- SEG4 ----->| |<--------------- PW2 --------------->| Figure 15 4.7. PW Label Distribution from Primary PE to Protector A primary PE MUST distribute the label of each primary PW to the protector that protects the PW. To achieve this, the primary PE MUST establish a targeted LDP session with the protector. For each primary PW, the primary PE SHOULD advertise over that session a Protection FEC Element via Label Mapping message. The Protection FEC Element is a new LDP FEC, and its encoding is described below. The PW's label is encoded in the message using the Upstream-Assigned Label TLV defined in (RFC 6389). The Protection FEC Element and the PW label combined represent the primary PE's forwarding state for the PW. The Label Mapping message SHOULD also carry an IPv4/v6 Interface_ID TLV (RFC 6389, RFC 3471) encoded with the context identifier of the {primary PE, protector}. The protector that receives this Label Mapping message SHOULD install a forwarding entry for the PW label in the label space identified by the context identifier. The nexthop of the forwarding entry SHOULD allow packets to be sent towards the target CE via a backup AC or a backup (S-)PE, depending on the protection model and SS-PW or MS-PW scenario involved. The Protection FEC Element has type 0x83. It is defined as below: Shen, et al. Expires December 27, 2012 [Page 22] Internet-Draft PW Endpoint Fast Failure Protection June 2012 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type(0x83) | Reserved | Encoding Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | | ~ PW Information ~ | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 16 - Encoding Type Type of format that PW Information field is encoded. - Length Length of PW Information field in octets. - PW Information Field of variable length that specifies a PW For Encoding Type, 1 is defined for the PWid FEC Element format, and 2 is defined for the Generalized PWid FEC Element format (RFC 4447). Shen, et al. Expires December 27, 2012 [Page 23] Internet-Draft PW Endpoint Fast Failure Protection June 2012 4.7.1. Protection FEC Element Encoding for PWid 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type(0x83) | Reserved | Enc Type(1) | Length(16) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Ingress PE Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Egress PE Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Group ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | PW ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |C| PW Type | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 17 - Ingress PE Address IP address of the ingress PE of PW. - Egress PE Address IP address of the egress PE of PW. - Group ID An arbitrary 32-bit value that represents a group of PWs and that is used to create groups in the PW space. - PW ID A non-zero 32-bit connection ID that, together with the PW Type field, identifies a particular PW. - Control word bit (C) A bit that flags the presence of a control word on this PW. If C = 1, control word is present; If C = 0, control word is not present. - PW Type Shen, et al. Expires December 27, 2012 [Page 24] Internet-Draft PW Endpoint Fast Failure Protection June 2012 A 15-bit quantity that represents the type of PW. 4.7.2. Protection FEC Element Encoding for Generalized PWid 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type(0x83) | Reserved | Enc Type(2) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Ingress PE Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Egress PE Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |C| PW Type | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | AGI Type | Length | Value | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ AGI Value (contd.) ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | AII Type | Length | Value | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ SAII Value (contd.) ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | AII Type | Length | Value | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ TAII Value (contd.) ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 18 - Ingress PE Address IP address of the ingress PE of PW. - Egress PE Address IP address of the egress PE of PW. - Control word bit (C) A bit that flags the presence of a control word on this PW. If C = 1, control word is present; If C = 0, control word is not present. Shen, et al. Expires December 27, 2012 [Page 25] Internet-Draft PW Endpoint Fast Failure Protection June 2012 - PW Type A 15-bit quantity that represents the type of PW. - AGI Type, Length, Value, AGI Value Attachment Group Identifier of PW. - SAII Type, Length, Value, SAII Value Source Attachment Individual Identifier of PW. - TAII Type, Length, Value, TAII Value Target Attachment Individual Identifier of PW. 4.8. PW Label Distribution from Backup PE to Protector In the centralized protector model, a protector may not be a backup (S-)PE for some primary PWs. For these PWs, in addition to learning PW labels from the primary PEs, the protector MUST also learn the labels of backup PWs and backup PW segments from backup (S-)PEs. To achieve this, each backup (S-)PE MUST establish a targeted LDP session with the protector. The backup PE SHOULD advertise over that session a Protection FEC Element for the backup PW via Label Mapping message. The content of this Protection FEC Element MUST match the Protection FEC Element that the primary PE advertises to the protector (section 4.8). The Label Mapping message SHOULD also include a Generic Label TLV encoded with the backup PW's label. The context identifier SHOULD NOT be encoded in Interface_ID TLV in this message. The Protection FEC Element and the backup PW's label combined represent the backup PE's forwarding state for the backup PW. The protector that receives this Label Mapping message SHOULD associate the backup PW with the primary PW, based on the common Protection FEC Element. It SHOULD distinguish between the message from the primary PE and the message from the backup PE based on the presence and absence of context identifier in Interface_ID TLV. It SHOULD install a forwarding entry for the primary PW's label in the label space identified by the context identifier. The nexthop of the forwarding entry SHOULD indicate a label swap to the backup PW's label. Shen, et al. Expires December 27, 2012 [Page 26] Internet-Draft PW Endpoint Fast Failure Protection June 2012 4.9. Revertive Behavior After a local repair takes effect, PW traffic is redirected from a PLR to a protector and then to target CE. There are three strategies for restoring the traffic to a fully working PW. o Global revertive mode If the ingress CE is multi-homed (Figure 1), it MAY switch the traffic to a backup AC which is bound to a backup PW. Or, if the ingress PE hosts a backup PW (Figure 2), it MAY switch the traffic to the backup PW. These procedures are referred to as global repairs, and are driven by ingress CE or ingress PE. Possible triggers of a global repair include PW status, OAM, and BFD. o Control plane revertive mode In egress PE node protection and S-PE node protection, it is possible that the failure is limited to the link between the PLR and the primary (S-)PE, while the primary (S-)PE is still up. In this case, if the PLR or an upstream router along the transport tunnel can reach the primary (S-)PE via an alternative route, it MAY reroute the transport tunnel around the failed link, so that the transport tunnel can continue to carry the PW traffic to the primary (S-)PE. This procedure is driven by control plane convergence, and is referred to as control plane repair. o Local revertive mode The PLR MAY move traffic back to the primary PW, after the failure is resolved. In egress AC protection, upon detecting that the primary AC is restored, the PLR MAY start forwarding traffic via the AC again. Likewise, in egress PE node protection and switching node protection, upon detecting that the primary PE is restored, the PLR MAY re-establish the primary transport tunnel, move the traffic back to the tunnel. These procedures are referred to as local reversion. The fast protection mechanism in this document SHOULD always be used in tandem with the globally revertive mode. Particularly in the case of egress (S-)PE failure, if the ingress PE or the protector loses communication with the (S-)PE for an extensive period of time, the LDP session between them may go down. Consequently, the ingress PE may bring down the primary PW, or the protector may delete the forwarding entry of the primary PW label from the label space. In either case, the service will be disrupted. In other words, although the fast protection can temporarily repair traffic, control plane states may eventually time out if the failure persists. Therefore, Shen, et al. Expires December 27, 2012 [Page 27] Internet-Draft PW Endpoint Fast Failure Protection June 2012 it is recommended that the global revertive mode SHOULD always be established in advance, so that it can move traffic to a fully working backup PW shortly after the local repair. The control plane revertive mode is optional, because it only applies to the specific scenarios of egress PE failure and S-PE failure. The local revertive mode is optional. In the circumstances where the failure is caused by resource flapping, local reversion MAY be dampened to limit potential disruptions. Local revertive mode MAY be disabled completely by configuration. 5. IANA Considerations IANA maintains a registry of LDP FECs at the registry "Label Distribution Protocol" in the sub-registry called "Forwarding Equivalence Class (FEC) Type Name Space". This document defines a new LDP Protection FEC Element in Section 4.7. IANA has assigned the type value 0x83 to it. 6. Security Considerations The security considerations discussed in RFC 5036, RFC 5331, RFC 3209, and RFC 4090 apply to this document. 7. Acknowledgements This document leverages work done by Hannes Gredler, Yakov Rekhter, Minto Jeyananth and several others on MPLS edge protection. Thanks to Nischal Sheth, Bhupesh Kothari, and Kevin Wang for their contribution. Thanks to Yakov Rekhter and John E Drake for reviewing the document. 8. References 8.1. Normative References [RFC3985] Bryant, S. and P. Pate, "Pseudo Wire Emulation Edge-to- Edge (PWE3) Architecture", RFC 3985, March 2005. [RFC5659] Bocci, M. and S. Bryant, "An Architecture for Multi- Segment Pseudowire Emulation Edge-to-Edge", RFC 5659, October 2009. Shen, et al. Expires December 27, 2012 [Page 28] Internet-Draft PW Endpoint Fast Failure Protection June 2012 [RFC4447] Martini, L., Rosen, E., El-Aawar, N., Smith, T., and G. Heron, "Pseudowire Setup and Maintenance Using the Label Distribution Protocol (LDP)", RFC 4447, April 2006. [RFC5331] Aggarwal, R., Rekhter, Y., and E. Rosen, "MPLS Upstream Label Assignment and Context-Specific Label Space", RFC 5331, August 2008. [RFC5036] Andersson, L., Minei, I., and B. Thomas, "LDP Specification", RFC 5036, October 2007. [RFC2205] Braden, B., Zhang, L., Berson, S., Herzog, S., and S. Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1 Functional Specification", RFC 2205, September 1997. [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels", RFC 3209, December 2001. [RFC4090] Pan, P., Swallow, G., and A. Atlas, "Fast Reroute Extensions to RSVP-TE for LSP Tunnels", RFC 4090, May 2005. [RFC5286] Atlas, A. and A. Zinin, "Basic Specification for IP Fast Reroute: Loop-Free Alternates", RFC 5286, September 2008. [RFC5714] Shand, M. and S. Bryant, "IP Fast Reroute Framework", RFC 5714, January 2010. [RFC3471] Berger, L., "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Functional Description", RFC 3471, January 2003. [RFC3472] Ashwood-Smith, P. and L. Berger, "Generalized Multi- Protocol Label Switching (GMPLS) Signaling Constraint- based Routed Label Distribution Protocol (CR-LDP) Extensions", RFC 3472, January 2003. [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol Label Switching Architecture", RFC 3031, January 2001. [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998. [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection (BFD)", RFC 5880, June 2010. [RFC6389] Aggarwal, R. and JL. Le Roux, "MPLS Upstream Label Assignment for LDP", RFC 6389, November 2011. Shen, et al. Expires December 27, 2012 [Page 29] Internet-Draft PW Endpoint Fast Failure Protection June 2012 [IP-LDP-FRR-MRT] Atlas, A. and R. Kebler, "An Architecture for IP/LDP Fast- Reroute Using Maximally Redundant Trees", draft-ietf-rtgwg-mrt-frr-architecture (work in progress), 2011. 8.2. Informative References [RFC5920] Fang, L., "Security Framework for MPLS and GMPLS Networks", RFC 5920, July 2010. Authors' Addresses Yimin Shen (editor) Juniper Networks 10 Technology Park Drive Westford, MA 01886 USA Phone: +1 9785890722 Email: yshen@juniper.net Rahul Aggarwal Arktan, Inc Email: raggarwa_1@yahoo.com Wim Henderickx Alcatel-Lucent Copernicuslaan 50 2018 Antwerp Belgium Email: wim.henderickx@alcatel-lucent.be Shen, et al. Expires December 27, 2012 [Page 30]