L3VPN Working Group IJsbrand Wijnands Internet Draft Eric C. Rosen Intended Status: Proposed Standard Cisco Systems, Inc. Updates: 6514 Expires: August 24, 2012 Uwe Joorde Deutsche Telekom February 24, 2012 Encoding mLDP FECs in the NLRI of BGP MCAST-VPN Routes draft-rosen-l3vpn-mvpn-mldp-nlri-00.txt Abstract Many service providers offer "BGP/MPLS IP VPN" service to their customers. Existing IETF standards specify the procedures and protocols that a service provider uses in order to offer this service to customers who have IP unicast and IP multicast traffic in their VPNs. It is also desirable to be able to support customers who have MPLS multicast traffic in their VPNs. This document specifies the procedures and protocol extensions that are needed to support customers who use the Multicast Extensions to Label Distribution Protocol (mLDP) as the control protocol for their MPLS multicast traffic. Existing standards do provide some support for customers who use mLDP, but only under a restrictive set of circumstances. This document generalizes the existing support to include all cases where the customer uses mLDP, without any restrictions. 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." Wijnands, et al. [Page 1] Internet Draft draft-rosen-l3vpn-mvpn-mldp-nlri-00.txt February 2012 The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Copyright and License Notice Copyright (c) 2012 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1 Introduction .......................................... 3 2 Why This Document is Needed ........................... 4 3 Encoding an mLDP FEC in the MCAST-VPN NLRI ............ 5 4 Wildcards ............................................. 7 5 IANA Considerations ................................... 8 6 Security Considerations ............................... 9 7 Acknowledgments ....................................... 9 8 Authors' Addresses .................................... 9 9 Normative References .................................. 10 10 Informative References ................................ 10 Wijnands, et al. [Page 2] Internet Draft draft-rosen-l3vpn-mvpn-mldp-nlri-00.txt February 2012 1. Introduction Many service providers (SPs) offer "BGP/MPLS IP VPN" service to their customers. When a customer has IP multicast traffic in its VPN, the service provider needs to signal the customer multicast states across the backbone. A customer with IP multicast traffic is typically using PIM ("Protocol Independent Multicast") [PIM] and/or IGMP ("Internet Group Management Protocol") [IGMP] as the multicast control protocol in its VPN. The IP multicast states of these protocols are commonly denoted as "(S,G)" and/or "(*,G)" states, where "S" is a multicast source address and "G" is a multicast group address. [MVPN-BGP] specifies the way an SP may use BGP to signal a customer's IP multicast states across the SP backbone. This is done by using "Multiprotocol BGP" Updates whose "Subsequent Address Family" value is "MCAST-VPN" (5). The NLRI ("Network Layer Reachability Information") field of these Updates includes a customer Multicast Source field and a customer Multicast Group field, thus enabling the customer's (S,G) or (*,G) states to be encoded in the NLRI. It is also desirable for the BGP/MPLS IP VPN service to be able to support customers who are using MPLS multicast, either instead of, or in addition to, IP multicast. This document specifies the procedures and protocol extensions needed to support customers who use mLDP ("Multicast Extensions to Label Distribution Protocol") [mLDP] to create and maintain Point-to-Multipoint (P2MP) and/or Multipoint-to- Multipoint (MP2MP) Label Switched Paths (LSPs). While mLDP is not the only protocol that can be used to create and maintain multipoint LSPs, consideration of other MPLS multicast control protocols is outside the scope of this document. When a customer is using mLDP in its VPN, the customer multicast states associated with mLDP are denoted by an mLDP "FEC Element" ("Forwarding Equivalance Class element", see [mLDP]), instead of by an (S,G) or (*,G). Thus it is necessary to have a way to encode a customer's mLDP FEC Elements in the NLRI field of the BGP MCAST-VPN routes. While [MVPN-BGP] does specify a way of encoding an mLDP FEC Element in the MCAST-VPN NLRI field, the encoding specified therein makes a variety of restrictive assumptions about the customer's use of mLDP. (These assumptions are described in section 2 of this document.) The purpose of this document is to update [MVPN-BGP] so that customers using mLDP in their VPNs can be supported even when those assumptions do not hold. The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this Wijnands, et al. [Page 3] Internet Draft draft-rosen-l3vpn-mvpn-mldp-nlri-00.txt February 2012 document are to be interpreted as described in [RFC2119]. 2. Why This Document is Needed An mLDP FEC Element consists of a FEC Type, a Root Node, and an Opaque Value. mLDP uses several FEC types, and in particular, uses the FEC type to distinguish between P2MP LSPs and MP2MP LSPs. Section 11.1.2 of [MVPN-BGP] ("Originating routes: mLDP as the C- multicast control protocol") states: Whenever a PE receives from one of its CEs a P2MP Label Map over interface I, where X is the Root Node Address, Y is the Opaque Value, and L is an MPLS label ... the PE constructs a Source Tree Join C-multicast route whose MCAST-VPN NLRI contains X as the Multicast Source field, and Y as the Multicast Group field. In other words, the Root Node of the mLDP FEC Element appears in the Multicast Source Field, and the Opaque Value of the mLDP FEC Element appears in the Multicast Group field. This method of encoding an mLDP FEC in an MCAST-VPN NLRI can only be used if all of the following conditions hold: 1. A customer using mLDP is not also using PIM/IGMP. The encoding in [MVPN-BGP] does not specify any way in which one can determine, upon receiving a BGP Update, whether the Multicast Group field contains an IP address or whether it contains an mLDP FEC Element Opaque Value. Therefore it may not uniquely identify a customer multicast state if the customer is using both PIM/IGMP and mLDP in its VPN. 2. A customer using mLDP is using only the mLDP P2MP FEC Element, and is not using the mLDP MP2MP FEC Element. The encoding in [MVPN-BGP] does not specify any way to encode the type of the mLDP FEC Element; it just assumes it to be a P2MP FEC Element. 3. A customer using mLDP is using only an mLDP Opaque Value type for which the Opaque Value is exactly 32 bits or 128 bits long. The use of Multicast Group fields that have other lengths is declared by [MVPN-BGP] to be "out of scope" of that document (see, e.g., section 4.3 of that document). Wijnands, et al. [Page 4] Internet Draft draft-rosen-l3vpn-mvpn-mldp-nlri-00.txt February 2012 This condition holds if the customer uses only the mLDP "Generic LSP Identifier" Opaque Value type (defined in [mLDP]). However, mLDP supports many other Opaque Value types whose length is not restricted to be 32 or 128 bits. The purpose of this document is to update [MVPN-BGP] so that customers using mLDP can be supported, even when these conditions do not hold. In addition, neither [MVPN-BGP] nor [MVPN-WILDCARDS] addresses the use of "wild cards" when the MCAST-VPN NLRI encodes an MLDP FEC. This document specifies a way to encode mLDP FEC Element wild cards in the NLRI of the relevant BGP MCAST-VPN routes. 3. Encoding an mLDP FEC in the MCAST-VPN NLRI This section specifies the way to encode an mLDP FEC element in the NLRI of the following three MCAST-VPN route types defined in [MVPN- BGP]: - C-multicast Source Tree Join, - S-PMSI A-D route, and - Leaf A-D route. The other four MCAST-VPN route types defined in [MVPN-BGP] do not ever need to carry mLDP FEC Elements. The C-multicast Shared Tree Join route and the Source Active A-D route are used to communicate state about unidirectional shared trees; since mLDP does not have unidirectional shared trees, these routes are not used to signal mLDP states. The Intra-AS I-PMSI A-D route and the Inter-AS I-PMSI A-D route do not identify specific customer multicast states, and hence do not carry any information that is specific to the customer's multicast control protocol. Per [MVPN-BGP], the first octet of the NLRI of an MCAST-VPN route is a "route type". Only values 1-7 are defined. The high order 5 bits of that octet are thus always zero. This document updates [MVPN-BGP] by specifying a use for the high order 2 bits of the "route type" octet. The following two values are defined: Wijnands, et al. [Page 5] Internet Draft draft-rosen-l3vpn-mvpn-mldp-nlri-00.txt February 2012 - If the two high order bits are both zero, the NLRI is as specified in [MVPN-BGP] and/or [MVPN-WILDCARDS]. - If the two high order bits have the value 01, the NLRI encoding is modified as follows: the "Multicast Source Length", "Multicast Source", "Multicast Group" length, and "Multicast Group" fields are omitted, and in their place is a single mLDP FEC Element, as defined in [mLDP]. See section 2.2 of [mLDP] for a diagram of the mLDP FEC element. The other two possible values (11 and 10) for the two high order bits may be used at a later time to identify other multicast control protocols. As a result, the NLRI of an S-PMSI A-D route with an mLDP FEC in its NLRI will consist of a Route Distinguisher, followed by the mLDP FEC, followed by the "Originating Router's IP Address Field". The NLRI of a C-multicast Source Tree Join route with an mLDP FEC in its NLRI will consist of a Route Distinguisher, followed by the Source AS, followed by the mLDP FEC. In a Leaf A-D route that has been derived from an S-PMSI A-D route, the "route key" field remains the NLRI of the S-PMSI A-D route from which it was derived. In a Leaf A-D route that has not been derived from an S-PMSI A-D route, the "route key" field is as specified in [SEGMENTED-MVPN], except that the "Multicast Source Length", "Multicast Source", "Multicast Group" length, and "Multicast Group" fields are omitted, and in their place is a single mLDP FEC Element. Thus the route key field consists of a Route Distinguisher, an MLDP FEC element, and the IP address of the Ingress PE router. An mLDP FEC element contains an "address family" field from IANA's "Address Family Numbers" registry. This identifies the address family of the "root node address" field of the FEC element. When an mLDP FEC element is encoded into the NLRI of an a BGP update whose SAFI is MCAST-VPN, the address family of the root node (as indicated in the FEC element) MUST "correspond to" the address family that is identified in the AFI field of that BGP update. These two "address family" fields are considered to "correspond" under the following conditions: - they contain identical values, or Wijnands, et al. [Page 6] Internet Draft draft-rosen-l3vpn-mvpn-mldp-nlri-00.txt February 2012 - the BGP update's AFI field identifies IPv4 as the address family, and the mLDP FEC element identifies "Multi-Topology IPv4" as the address family of the root node, or - the BGP update's AFI field identifies IPv6 as the address family, and the mLDP FEC element identifies "Multi-Topology IPv6" as the address family of the root node. For more information about the "multi-topology" address families, see [LDP-MT] and [mLDP-MT]. 4. Wildcards [MVPN-WILDCARDS] specifies encodings and procedures that allow "wildcards" to be specified in the NLRI of S-PMSI A-D routes. A set of rules are given that specify when a customer multicast flow "matches" a given S-PMSI A-D route whose NLRI contains wildcards. However, the use of these wildcards is defined only for the case where the customer is using PIM as its multicast control protocol. In this section, we define the wildcard encodings for the case where the customer is using mLDP as its multicast control protocol. Customer mLDP Multipoint LSPs do NOT ever match S-PMSI A-D routes containing the wildcards specified in [MVPN-WILDCARDS]. To specify a wildcard that can be matched by a customer mLDP Multipoint LSP, one encodes an mLDP "typed wildcard FEC" [LDP-WC] into the NLRI of the S-PMSI A-D route. The mLDP typed wildcard FEC is specified in section 9 of [mLDP], which includes the following diagram: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Typed Wcard | Type | Len = 2 | AFI ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ | +-+-+-+-+-+-+-+-+ The field "Typed Wcard" contains the value in the IANA LDP Registry "Forwarding Equivalence Class (FEC) Type Name Space" that is assigned to "Typed Wildcard FEC Element" (i.e., 5). The AFI field contains an address family identifier, from IANA's Wijnands, et al. [Page 7] Internet Draft draft-rosen-l3vpn-mvpn-mldp-nlri-00.txt February 2012 "Address Family Numbers" registry. The "Type" field MUST either be set to zero, or contain one of the following values from the IANA LDP Registry "Forwarding Equivalence Class (FEC) Type Name Space": - P2MP FEC (6) - MP2MP-Up FEC (7) - MP2MP-Down FEC (8) If the type field is set to "P2MP-FEC", the wildcard FEC element means "any P2MP FEC whose root node address is of the specified address family". If the type field is set to "MP2MP-Up" or "MP2MP-Down", the wildcard FEC element means "any MP2MP FEC" whose root node address is of the specified address family. When generating this wildcard FEC, the value "MP2MP-Down" SHOULD be used. If the type field is set to 0, the wildcard FEC element means "any P2MP or MP2MP" FEC whose root node address is of the specified address family. A future revision of this document will discuss use cases, and provide a more detailed set of procedures for using these wildcards. 5. IANA Considerations [MVPN-BGP] does not create a registry for the allocation of new MCAST-VPN Route Type values. In retrospect, it seems that it should have done so. IANA should create a registry called "MCAST-VPN Route Types", referencing this document and [MVPN-BGP]. The allocation policy should be "Standards Action with Early Allocation", and the assignable values are in the range 0-0xFF. The following values should be assigned: - 0x00: Reserved - 0x01: Intra-AS I-PMSI A-D route (reference: [MVPN-BGP]) - 0x02: Inter-AS I-PMSI A-D route (reference: [MVPN-BGP]) Wijnands, et al. [Page 8] Internet Draft draft-rosen-l3vpn-mvpn-mldp-nlri-00.txt February 2012 - 0x03: S-PMSI A-D route for PIM as the C-multicast control protocol (reference: [MVPN-BGP]) - 0x43: S-PMSI A-D route for mLDP as the C-multicast control protocol (reference: this document) - 0x04: Leaf A-D route for PIM as the C-multicast control protocol (reference: [MVPN-BGP]) - 0x44: Leaf A-D route for mLDP as the C-multicast control protocol (reference: this document) - 0x05: Source Active A-D route for PIM as the C-multicast control protocol (reference: [MVPN-BGP]) - 0x06: Shared Tree Join route for PIM as the C-multicast control protocol (reference: [MVPN-BGP]) - 0x07: Source Tree Join route for PIM as the C-multicast control protocol (reference: [MVPN-BGP]) - 0x47: Source Tree Join route for mLDP as the C-multicast control protocol (reference: this document) 6. Security Considerations No new security issues. 7. Acknowledgments The authors wish to think Pradosh Mohapatra and Saquib Najam for their ideas and comments. We also thank Yakov Rekhter for his comments. 8. Authors' Addresses IJsbrand Wijnands Cisco Systems, Inc. De kleetlaan 6a Diegem 1831 Belgium E-mail: ice@cisco.com Wijnands, et al. [Page 9] Internet Draft draft-rosen-l3vpn-mvpn-mldp-nlri-00.txt February 2012 Eric C. Rosen Cisco Systems, Inc. 1414 Massachusetts Avenue Boxborough, MA, 01719 E-mail: erosen@cisco.com Uwe Joorde Deutsche Telekom Hammer Str. 216-226 D-48153 Muenster, Germany E-mail: Uwe.Joorde@telekom.de 9. Normative References [LDP-WC] Asati, R., Minei, I., and B. Thomas, "Label Distribution Protocol (LDP) 'Typed Wildcard' Forward Equivalence Class (FEC)", RFC 5918, August 2010. [mLDP] "Label Distribution Protocol Extensions for Point-to- Multipoint and Multipoint-to-Multipoint Label Switched Paths", Wijnands, Minei, Kompella, Thomas, RFC 6388, November 2011 [MVPN-BGP] "BGP Encodings and Procedures for Multicast in MPLS/BGP IP VPNs", Aggarwal, Rosen, Morin, Rekhter, RFC 6514, February 2012 [MVPN-WILDCARDS], "Wildcards in Multicast VPN Auto-Discovery Routes", draft-ietf-l3vpn-mvpn-wildcards-02.txt, February 2012 [RFC2119] "Key words for use in RFCs to Indicate Requirement Levels.", Bradner, March 1997 10. Informative References [IGMP] "Internet Group Management Protocol, Version 3", Cain, Deering, Kouvelas, Fenner, Thyagarajan, RFC 3376, October 2002 [LDP-MT] "LDP Extension for Multi-Topology Support", Zhao, et. al., draft-ietf-mpls-ldp-multi-topology-02.txt, November 2011 [mLDP-MT] "mLDP Extensions for Multi Topology Routing", Wijnands, Raza, draft-iwijnand-mpls-mldp-multi-topology-01.txt, January 2012 [PIM] "Protocol Independent Multicast - Sparse Mode (PIM-SM)", Fenner, Handley, Holbrook, Kouvelas, August 2006, RFC 4601 Wijnands, et al. [Page 10] Internet Draft draft-rosen-l3vpn-mvpn-mldp-nlri-00.txt February 2012 [SEGMENTED-MVPN] "Inter-Area P2MP Segmented LSPs", Rekhter, Aggarwal, Morin, Grosclaude, Leymann, Saad, draft-ietf-mpls-seamless- mcast-03.txt, December 2011 Wijnands, et al. [Page 11]