INTERNET-DRAFT Mingui Zhang Intended Status: Proposed Standard Peng Zhou Expires: April 24, 2014 Huawei Russ White Verisign October 21, 2013 Label Sharing for Fast PE Protection draft-zhang-l3vpn-label-sharing-01.txt Abstract This document describes a method to be used by Service Providers to provide fast protection of VPN connections for a CE. Egress PEs in a redundant group always assign the same label for VPN routes from a VRF. These egress PEs create a BGP virtual Next Hop (vNH) in the domain of the IP/MPLS backbone network as an agent of the CE router. Primary and backup tunnels terminated at the vNH are set up by the BGP/MPLS IP VPN based on IGP FRR. If the primary egress PE fails, the backup egress PEs can recognize the "shared" VPN route label, so that the failure affected traffic can be smoothly switched to the backup PE for delivery without changing its VPN route label. Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/1id-abstracts.html The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html Copyright and License Notice Copyright (c) 2013 IETF Trust and the persons identified as the Mingui Zhang Expires April 24, 2014 [Page 1] INTERNET-DRAFT Label Sharing for Fast PE Protection October 21, 2013 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 1.1. Conventions used in this document . . . . . . . . . . . . . 3 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3 2. The Label Sharing Method . . . . . . . . . . . . . . . . . . . 3 2.1. The Virtual Next Hop . . . . . . . . . . . . . . . . . . . 4 2.2. Link Costs Set Up for IGP FRR . . . . . . . . . . . . . . . 5 2.3 Label Assignment and Processing . . . . . . . . . . . . . . 6 2.3.1. The VPN Route Label . . . . . . . . . . . . . . . . . . 6 2.3.2. The Tunnel Label . . . . . . . . . . . . . . . . . . . 6 3. Security Considerations . . . . . . . . . . . . . . . . . . . . 7 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7 5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7 5.1. Normative References . . . . . . . . . . . . . . . . . . . 7 5.2. Informative References . . . . . . . . . . . . . . . . . . 8 Appendix A: Generating OSPF LSAs . . . . . . . . . . . . . . . . . 8 Appendix B: Generating ISIS LSPs . . . . . . . . . . . . . . . . . 10 Author's Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13 Mingui Zhang Expires April 24, 2014 [Page 2] INTERNET-DRAFT Label Sharing for Fast PE Protection October 21, 2013 1. Introduction For the sake of reliability, ISPs usually connect one CE to multiple PEs. When the primary egress PE fails, a backup egress PE continues to offer VPN connectivity to the CE. If local repair is performed by the upstream neighbor of the primary egress PE on the data path, it's possible to achieve a 50msec switchover. VPN routes learnt from CEs are distributed by egress PEs to ingress PEs that need to know these VPN routes. Egress PEs in a redundant group (RG) MUST allocate the same VPN route label for routes of the same VPN. When the primary egress PE fails, data packets are redirected to a backup egress PE by the PLR (Point of Local Repair) router, the backup PE can recognize the VPN route label in these data packets and deliver them correctly. The method developed in this document is so called "Label Sharing for Fast PE Protection". This document supposes BGP/MPLS IP VPN is deployed on the backbone and Label Distribution Protocol (LDP) is used to distribute MPLS labels. Through generating virtual LSAs/LSPs in OSPF/ISIS, egress PEs in an RG create a virtual router (the vNH) in the domain of IP/MPLS backbone to represent the CE router. When the VPN route is distributed, those egress PEs use vNH as the "BGP next hop". The vNH will be treated as the egress point of the tunnel by other routers. Metrics for the virtual links attached to the vNH are set up in a way that the IGP FRR mechanism defined in [LFA] can be leveraged to achieve local protection when the PLR detects the primary egress PE fails. 1.1. 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 [RFC2119]. 1.2. Terminology VRF: Virtual Routing and Forwarding table FRR: Fast ReRouting PLR: Point of Local Repair LFA: loop-free alternate 2. The Label Sharing Method Mingui Zhang Expires April 24, 2014 [Page 3] INTERNET-DRAFT Label Sharing for Fast PE Protection October 21, 2013 +====================================+ +---+ | +---+ +--+ +---+ M | |CE1+----+PE1+----+P1+----+PE3+-------+ | +---+ | +-+-+ +-++ +---+ 1100| | | | | | +-+-+ | +---+ | | | | +vNH+----+CE2| | | | | +-+-+ | +---+ +---+ | +-+-+ +-++ +---+ 1100| | |CE3+----+PE2+----+P2+----+PE4+-------+ | +---+ | +---+ +--+ +---+ S | | | | IP/MPLS Backbone Network | +====================================+ Figure 2.1: Egress PE routers share the same VPN route label 1100. A CE router is usually connected to multiple PE routers of the IP/MPLS backbone network for the sake of reliability. Figure 2.1 shows such a scenario. In this document, PE1 and PE2 are defined as ingress routers and PE3 and PE4 are defined as egress routers. Suppose PE3 is the primary PE while PE4 is the backup egress PE. Those egress PE routers may discover each other as in the same RG from the CE routes learning process which can be a dynamic routing algorithm or a static routing configuration [RFC4364]. In this document, we suppose there are two PEs in one RG. It's possible to expand the method to support more than two PEs in one RG. 2.1. The Virtual Next Hop A vNH router is created in IGP to represent the set of CEs which are dual-homed to the same egress PEs in the Service Provider's backbone. A master PE is elected in the same way the DR is selected (see section 7.3 of [RFC2328]), or the DIS is selected [ISIS]. This master PE determines the loopback IP address for the vNH. This loopback IP address can be configured manually or assigned automatically. The SystemID of the vNH under ISIS is composed based on this loopback IP address. The master PE generates the router link state information (LSA/LSP) on behalf of the vNH. Links to each PE and each CE in the group are included in router link state information PDUs of the PE and CE. Multiple vNHs may be created for one CE. Then multiple tunnels can be set up from ingress PEs to the vNHs. Ingress PEs can choose from these tunnel routes to achieve load balance for the CE. The overload mode MUST be set so that the rest routers in the network will not route transit traffic through the vNH. In OSPF, the overload mode can be set up through setting the link weights from the vNH to Mingui Zhang Expires April 24, 2014 [Page 4] INTERNET-DRAFT Label Sharing for Fast PE Protection October 21, 2013 egress PEs to the maximum link weight which is 0xFFFF. In ISIS, this overload mode is realized as setting the overload bit in the LSP of the vNH. See Appendix A and B for the detail setting up of LSAs/LSPs. 2.2. Link Costs Set Up for IGP FRR |<------ Sxy3-------->| +-------Px(PLR)-------PE3 | | \ M | | \ Pxy C34| vNH | | / | | / S +---------------------PE4 |<------ Sxy4-------->| Figure 2.2: The illustration of equations. LSP tunnels are set up based on IGP routes through LDP signaling. If the IGP costs for the links between egress PEs and the vNH can be set up in a way that one egress PE appears on the primary path while the other PE appears on the backup path, the PLR can make use of the multiple egress PEs to achieve fast failure protection. Link weights can be set up according to the following rule in order to leverage the well supported [LFA] as the IGP FRR mechanism. 1. This document supposes bidirectional link weights are being used. As illustrated in Figure 2.2, assume the weight for the link between PE3 and vNH is "M" and the weight for the link between PE4 and vNH is "S". The weight for the link between PE3 and PE4 is C34. 2. Px is a neighbor of PE3. This Px will act as the PLR. Suppose Pxy is Px's neighbor with the shortest path to PE4, after PE3 is removed from the topology. The cost of this path is Sxy4. 3. Add PE3 back to the topology. The cost of the path from Pxy to PE3 is Sxy3. 4. "M" and "S" can be set up as long as the following two equations hold. eq1: Sxy4+S < Sxy3+M eq2: C34+S > M Mingui Zhang Expires April 24, 2014 [Page 5] INTERNET-DRAFT Label Sharing for Fast PE Protection October 21, 2013 The eq1 guarantees that Pxy is safe, i.e., no loop occurs, to be used as the next hop by the PLR for bypass. The eq2 is designed to insure that the primary path does not go through the primary egress PE and backup egress PE in series. Although this document designs the method based on [LFA] which is widely deployed, other IGP FRR mechanisms can also be utilized to achieve the protection. For example, [MRT] is applicable regardless of how the link weights are set up. 2.3 Label Assignment and Processing 2.3.1. The VPN Route Label Egress PEs use BGP to distribute to ingress PEs the routes that they learn from CEs [RFC4364]. When egress PEs in an RG distribute the routes of the VPN that the CE is in, they MUST assign the same "VPN route label" for one VPN (per VRF label assignment). This label will become the first label of a data packet. The IP address of the vNH is used as the "BGP next hop". For example, in Figure 2.1, both PE3 and PE4 use 1100 as the VPN route label for the routes learnt from CE2. The shared label may be manually configured or negotiated through signaling between egress PEs. [LS-ICCP] extends [ICCP] and defines application TLVs to achieve such kind of signaling. If global label is supported, egress PEs in the RG may use the global label as the shared label. For global label, see Section 3.2.2/[G-use] and [G- frame] for more information. Suppose PE3 fails and the packet with VPN route label 1100 is redirected to PE4. PE4 can recognize this shared label. It simply looks up the packet's destination address in the VRF identified by this label. As specified in Section 5 of [RFC4364], PE4 will be able to determine, the attachment circuit over which the packet should be transmitted (to the CE) as well as the data link layer header for that interface. In this way, the failed egress PE is smoothly protected. The handling of PE-CE link failure is out the scope of this document. When the PE-CE link on the primary path fails, the primary PE may resort to existing PE-CE protection mechanisms. It might require that the backup PE had advertised the route to CE using its own IP address as the BGP next hop. When this route is advertised, its preference should be turned down so that the route 'advertised' by the vNH always precedes. 2.3.2. The Tunnel Label Mingui Zhang Expires April 24, 2014 [Page 6] INTERNET-DRAFT Label Sharing for Fast PE Protection October 21, 2013 In this document, all operations on the tunnel label are widely supported on existing PEs. Suppose Label Distribution Protocol is being used to distribute MPLS labels. The LSP tunnel follows an IGP route from ingress PEs to the vNH. The backup path to vNH can be calculated according to existing IGP FRR mechanism, such as [MRT] and [LFA]. The ingress PE tunnels the data packet through the backbone network using the "tunnel label" as the second entry of the label stack. The "VPN route label" is not visible again until the MPLS packet reaches the egress PE. The egress PE pops the second label and deliver the packet according to the "VPN route label". 3. Security Considerations This document raises no new security issues. 4. IANA Considerations This document requires no IANA actions. RFC Editor: please remove this section before publication. 5. References 5.1. Normative References [LFA] Filsfils, C., Ed., Francois, P., Ed., Shand, M., Decraene, B., Uttaro, J., Leymann, N., and M. Horneffer, "Loop-Free Alternate (LFA) Applicability in Service Provider (SP) Networks", RFC 6571, June 2012. [RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private Networks (VPNs)", RFC 4364, February 2006. [ICCP] L. Martini, S. Salam, et al, "Inter-Chassis Communication Protocol for L2VPN PE Redundancy", draft-ietf-pwe3-iccp- 11.txt, work in progress. [ISIS] ISO, "Intermediate system to Intermediate system routeing information exchange protocol for use in conjunction with the Protocol for providing the Connectionless-mode Network Service (ISO 8473)," ISO/IEC 10589:2002. [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998. [RFC1213] McCloghrie, K. and M. Rose, "Management Information Base for Network Management of TCP/IP-based internets:MIB-II", STD 17, RFC 1213, March 1991. Mingui Zhang Expires April 24, 2014 [Page 7] INTERNET-DRAFT Label Sharing for Fast PE Protection October 21, 2013 [LS-ICCP] M. Zhang, P. Zhou, "ICCP Application TLVs for VPN Route Label Sharing", draft-zhang-pwe3-iccp-label-sharing-00.txt, work in progress 5.2. Informative References [MRT] A. Atlas, Ed., R. Kebler, et al, "An Architecture for IP/LDP Fast-Reroute Using Maximally Redundant Trees", draft-ietf-rtgwg-mrt-frr-architecture-03.txt, work in progress. [G-use] Z. Li and Q. Zhao, "Use Cases of MPLS Global Label", draft- li-mpls-global-label-usecases-00.txt, work in progress. [G-frame] Z. Li and Q. Zhao, and T. Yang, "A Framework of MPLS Global Label", draft-li-mpls-global-label-framework-00.txt, work in progress. Appendix A: Generating OSPF LSAs The following Type 1 Router-LSA is flooded by the egress PE with the highest priority. As defined in [RFC2328], this LSA can only be flooded throughout a single area. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LS age | Options | LS type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link State ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Advertising Router | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LS sequence number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LS checksum | length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 0 |V|E|B| 0 | # links | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link Data | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | # TOS | metric | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | TOS | 0 | TOS metric | Mingui Zhang Expires April 24, 2014 [Page 8] INTERNET-DRAFT Label Sharing for Fast PE Protection October 21, 2013 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link Data | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ... | LS age The time in seconds since the LSA was originated. (Set to 0x708 by default.) Options As defined in [RFC2328], options = (E-bit). LS type 1 Link State ID Same as the Advertising Router Advertising Router The Router ID of the vNH. LS sequence number As defined in [RFC2328]. LS checksum As defined and computed in [RFC2328]. length The length in bytes of the LSA. This includes the 20 byte LSA header. (As defined and computed in [RFC2328].) VEB As defined in [RFC2328], set its value to 000. #links The number of router links described in this LSA. It equals to the number of Egress PEs in the RG. The following fields are used to describe each router link connected to an egress PE. Each router link is typed as Type 1 Point-to-point connection to another router. Link ID The Router ID of one of the egress PEs in the RG. Link Data Mingui Zhang Expires April 24, 2014 [Page 9] INTERNET-DRAFT Label Sharing for Fast PE Protection October 21, 2013 It specifies the interface's MIB-II [RFC1213] ifIndex value. It ranges between 1 and the value of ifNumber. The ifNumber equals to the number of the PEs in the RG. The PE with the highest priority sorts the PEs according to their unsigned integer Router ID in the ascend order and assigns the ifIndex for each. Type Value 1 is used, indicating the router link is a point-to-point connection to another router. # TOS This field is set to 0 for this version. Metric It is set to 0xFFFF. The fields used here to describe the virtual router links are also included in the Router-LSA of each egress PEs. The Link ID is replaced with the Router ID of the vNH. The Link Data specifies the interface's MIB-II [RFC1213] ifIndex value. The "Metric" field is set as defined in Section 2.2. Appendix B: Generating ISIS LSPs The primary egress PE generates the following level 1 LSP to describe the vNH node. No. of octets +-------------------------+ | Intradomain Routeing | 1 | Protocol Discriminator | +-------------------------+ | Length Indicator | 1 +-------------------------+ | Version/Protocol ID | 1 | Extension | +-------------------------+ | ID Length | 1 +-------------------------+ |R|R|R| PDU Type | 1 +-------------------------+ | Version | 1 +-------------------------+ | Reserved | 1 +-------------------------+ | Maximum Area Address | 1 +-------------------------+ Mingui Zhang Expires April 24, 2014 [Page 10] INTERNET-DRAFT Label Sharing for Fast PE Protection October 21, 2013 | PDU Length | 2 +-------------------------+ | Remaining Lifetime | 2 +-------------------------+ | LSP ID | ID Length + 2 +-------------------------+ | Sequence Number | 4 +-------------------------+ | Checksum | 2 +-------------------------+ |P|ATT|LSPDBOL|IS Type | 1 +-------------------------+ : Variable Length Fields : Variable +-------------------------+ Intradomain Routeing Protocol Discriminator - 0x83 (as defined in [ISIS]) Length Indicator - Length of the Fixed Header in octets Version/Protocol ID Extension - 1 ID Length - As defined in [ISIS] PDU Type (bits 1 through 5) - 18 Version - 1 Reserved - transmitted as zero, ignored on receipt Maximum Area Address - same as the primary egress PE PDU Length - Entire Length of this PDU, in octets, including the header. Remaining Lifetime - Number of seconds before this LSP is considered expired. (Set to 0x384 by default.) LSP ID - the system ID of the source of the LSP. It is structured as follows: +-------------------------+ | Source ID | 6 +-------------------------+ | Pseudonode ID | 1 +-------------------------+ | LSP Number | 1 +-------------------------+ Mingui Zhang Expires April 24, 2014 [Page 11] INTERNET-DRAFT Label Sharing for Fast PE Protection October 21, 2013 Source ID - SystemID of the vNH Pseudonode ID - Transmitted as zero LSP Number - Fragment number Sequence Number - sequence number of this LSP (as defined in [ISIS]) Checksum - As defined and computed in [ISIS] P - Bit 8 - 0 ATT - Bit 7-4 - 0 LSDBOL - Bit 3 - 1 IS Type - Bit 1 and 2 - bit 1 set, indicating the vNH is a Level 1 Intermediate System In the Variable Length Field, each link outgoing from the vNH to an egress PE is depicted by a Type #22 Extended Intermediate System Neighbors TLV [RFC5305]. The egress PE is identified by the 6 octets SystemID plus one octet of all-zero pseudonode number. The 3 octets metric is set as that in Section 2.2. None sub-TLVs is used by this version, therefore the value of the one octet length of sub-TLVs is 0. The Type #22 TLV requires 11 octets. The Type #22 TLV is also included in the LSP of each egress PE to depict the incoming link of the vNH. Only the 6 octets SystemID is replaced with the SystemID of the vNH. Mingui Zhang Expires April 24, 2014 [Page 12] INTERNET-DRAFT Label Sharing for Fast PE Protection October 21, 2013 Author's Addresses Mingui Zhang Huawei Technologies No.156 Beiqing Rd. Haidian District, Beijing 100095 P.R. China Email: zhangmingui@huawei.com Peng Zhou Huawei Technologies No.156 Beiqing Rd. Haidian District, Beijing 100095 P.R. China Email: Jewpon.zhou@huawei.com Russ White Verisign 12061 Bluemont Way Reston, VA 20190 USA Email: riwhite@verisign.com Mingui Zhang Expires April 24, 2014 [Page 13]