MPLS Working Group IJsbrand Wijnand Internet Draft Cisco Systems, Inc. Intended status: Standards Track Expires: May 13, 2012 Kamran Raza Cisco Systems, Inc. November 14, 2011 mLDP Extensions for Multi Topology Routing draft-iwijnand-mpls-mldp-multi-topology-00.txt Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. This document may not be modified, and derivative works of it may not be created, except to publish it as an RFC and to translate it into languages other than English. 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/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html This Internet-Draft will expire on May 13, 2012. Copyright Notice Copyright (c) 2011 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 Wijnands, et. al Expires May 2012 [Page 1] Internet-Draft mLDP Extensions for Multi-Topology Routing November 2011 carefully, as they describe your rights and restrictions with respect to this document. Abstract The Multi-Topology Routing (MTR) enables service differentiation through class-based forwarding. IGP protocols (OSPF and IS-IS) have already been extended to setup MTR. In order to deploy mLDP in an MTR setup, mLDP is also required to become topology-aware. This document specifies extensions to mLDP to support Multi-Topology Routing. Table of Contents 1. Glossary ..........................................................2 2. Introduction ......................................................3 3. Conventions used in this document .................................4 4. MT-Scoped mLDP FEC ................................................4 4.1.1 New MT IP Address Families .................................4 4.1.2 MT MP FEC Element ..........................................5 4.2 Topology IDs ...................................................6 5. Multipoint MT Capability...........................................7 6. MT Applicability on FEC-based features ............................8 6.1 Typed Wildcsrd MP FEC Elements ................................8 6.2 End-of-LIB .....................................................8 7. Topology-Scoped Forwarding ........................................9 7.1 Upstream LSR selection .........................................9 7.2 Downstream forwarding interface ................................9 8. Security Considerations ...........................................9 9. IANA Considerations ..............................................10 10. References ......................................................10 9.1. Normative References .........................................10 9.2. Informative References .......................................11 10. Acknowledgments .................................................11 1. Glossary MT - - Multi-Topology MT-ID Multi-Topology Identifier Wijnands, et. al Expires May 2012 [Page 2] Internet-Draft mLDP Extensions for Multi-Topology Routing November 2011 MTR - - Multi-Topology Routing IGP - - Interior Gateway Protocol mLDP - - Multi-point LDP P2MP - - Point-to-Multipoint MP2MP - - Multipoint-to-Multipoint MP - Multi-point (P2MP or MP2MP) LSP - - Label Switched Path 2. Introduction The Multi-Topology Routing (MTR) enables service differentiation through class-based forwarding. For example, MTR can be used to define separate IP topologies for voice, video, and data traffic classes. To support MTR, an IGP maintains independent IP topologies, termed as "Multi-Topologies" (MT), and computes/installs routes per topology. OSPF extensions [RFC4915] and ISIS extensions [RFC5120] specify the MT extensions under respective IGP. To support IGP MT, similar extensions [MT-LDP] have been proposed in LDP to make LDP MT-aware, and be able to setup unicast Label Switched Paths (LSPs) along IGP MT routing paths. Multi-point LDP (mLDP) refers to extensions in LDP to setup multi- point LSPs, point-to-multipoint (P2MP) or multipoint-to-multipoint (MP2MP), by means of set of extensions and procedures defined in [RFC6388]. In order to work in an MTR setup to take advantage of MTs, it is a natural extension to make mLDP become MT-aware. This document specifies the extensions to mLDP to support IGP Multi- Topology Routing (MTR). [Editor Note: This document will be updated and synchronized with MT LDP [MT-LDP] specification as/when MT LDP specification is updated] 3. 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]. 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. Wijnands, et. al Expires May 2012 [Page 3] Internet-Draft mLDP Extensions for Multi-Topology Routing November 2011 4. MT-Scoped mLDP FECs The Multi-Topology Identifier (MTID) is an identifier that is used to associate an MP LSP with a certain MTR topology. This identifier is part of the mLDP FEC encoding. It is part of the FEC encoding because LDP peers may want to setup an MP LSP via their own defined MTR policy. In order to avoid conflicting MTR policies for the same mLDP FEC, the MTID needs to be a part of the FEC, so that different MTID values will result in unique MP-LSP FEC elements. Since the MTID is part of the FEC, it will apply to all the LDP messages that potentially include an mLDP FEC element. Following subsections propose the extensions to bind an mLDP FEC to a topology. 4.1.1. New MT IP Address Families To extend IP address families for MT, we propose two new Address Families named "MT IP" and "MT IPv6" that can be used to specify IP prefixes within a topology scope. The format of the data associated with these new Address Family is: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | (IP) Prefix | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | MT-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: MT IP Address Families Data Format Where "(IP) Prefix" is an IPv4 and IPv6 address for "MT IP" and "MT IPv6" AF respectively, and the field "MT-ID" corresponds to 16-bit Topology ID for given prefix. The Address Family length incorporates both the (IP) Prefix field, as well as following 4-octets for MT. For MT IP and MT IPv6 AF, the AF length is 8 and 20 octets respectively. 4.1.2. MT MP FEC Element Base mLDP specification [RFC6388] defines MP FEC Element as follows: Wijnands, et. al Expires May 2012 [Page 4] Internet-Draft mLDP Extensions for Multi-Topology Routing November 2011 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MP FEC type | AF (IP/IPv6) | AF Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Root Node Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Opaque Length | Opaque Value | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: MP FEC Element Format [RFC6388] Where "Root Node Address" encoding is as defined for given "Address Family", and whose length (in octets) is specified by the "AF Length" field. To extend MP FEC elements for MT, the MTID is an identifier that is relevant in the context of the root address of the MP LSP. The MTID identifier determines in which topology the root address needs to be resolved. Since the MTID should be considered part of the mLDP FEC, the most natural place to encode the MTID is as part of the root address. For that reason we are proposing to use new MT IP Address Family as defined in Section 4.1.1. For MT mLDP, the MP FEC element's "Address Family" field will be set to "MT IP" or "MT IPv6", and the FEC element will be encoded as follows: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MP FEC type | AF (MT IP/ MTIPv6) | AF Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Root Node Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | MT-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Opaque Length | Opaque Value | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: MT-Scoped MP FEC Element Format Wijnands, et. al Expires May 2012 [Page 5] Internet-Draft mLDP Extensions for Multi-Topology Routing November 2011 In the context of this document, the applicable LDP FECs for MT mLDP include: o MP FEC Elements: o P2MP (0x6) o MP2MP Upstream (0x7) o MP2MP Downstream (0x8) o Typed Wildcard FEC Element(0x5) In case of "Typed Wildcard FEC Element", the sub FEC MUST be one of the MP FECs listed above. This specification allows the use of Topology-scoped mLDP FECs in LDP label and notification messages, as applicable. 4.2. Topology IDs This document assumes the same definitions and procedures associated with MT-ID as defined in [MT-LDP] specification. Additionally, it defines following special topology values: Default Topology (0x0): Used for backward compatibility) Wildcard Topology (0xffff): Used for wildcard label operations. 5. Multipoint MT Capability "Multipoint MT Capability" is a new LDP capability, defined in accordance with LDP Capability definition guidelines [RFC5561], that is to be advertised to its peers by an mLDP speaker to announce its capability to support MTR and the procedures specified in this document. This capability MAY be sent either in an Initialization message at the session establishment time, or in a Capability message dynamically during the lifetime of a session (only if "Dynamic Announcement" capability [RFC5561] has been successfully negotiated with the peer). The format of this capability is as follows: Wijnands, et. al Expires May 2012 [Page 6] Internet-Draft mLDP Extensions for Multi-Topology Routing November 2011 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |U|F| Multipoint MT Cap.(IANA) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |S| Reserved | +-+-+-+-+-+-+-+-+ Figure 1 : "Multipoint MT Capability" TLV Format Where: U- and F-bits: MUST be 1 and 0, respectively, as per Section 3 of LDP Capabilities [RFC5561]. Multipoint MT: TLV type (IANA assigned). Length: The length (in octets) of TLV. The value of this field MUST be 1 as there is no Capability-specific data [RFC5561] that follows in the TLV. S-bit: MUST be 1 if used in LDP Initialization message. MAY be set to 0 or 1 in dynamic Capability message to advertise or withdraw the capability respectively. An mLDP speaker that has successfully advertised and negotiated "Multipoint MT" capability MUST support the following: 1. Topology-scoped mLDP FECs in LDP messages ( Section 4. ) 2. Topology-scoped mLDP forwarding setup ( Section 7. ) 6. MT Applicability on FEC-based features 6.1. Typed Wildcard MP FEC Elements RFC5918 extends base LDP and defines Typed Wildcard FEC Element framework [RFC5918]. Typed Wildcard FEC element can be used in any LDP message to specify a wildcard operation/action for given type of FEC. The MT extensions proposed in document do not require any extension in procedures for Typed Wildcard Prefix FEC element, and these procedures apply as-is to Multipoint MT FEC wildcarding. The MT extensions, though, allow use of "MT IP" or "MT IPv6" in the Address Family field of the Typed Wildcard FEC element in order to use Wijnands, et. al Expires May 2012 [Page 7] Internet-Draft mLDP Extensions for Multi-Topology Routing November 2011 wildcard operations in the context of a given topology. The use of MT-scoped address family also allows us to specify MT-ID in these operations. This document extends Typed Wildcard MP FEC element encoding for MT as follows: 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 (5)| Type = MP FEC | Len = 6 | AF = MT IP ..| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |... or MT IPv6 | Reserved | MT ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |MT ID (contd.) | +-+-+-+-+-+-+-+-+ Fig 6: "Typed Wildcard MP FEC Element" for MT The proposed format allows an LSR to perform wildcard MP FEC operations under the scope of a topology. 6.2. End-of-LIB [RFC5919] specifies extensions and procedures for an LDP speaker to signal its convergence for given FEC type towards a peer. The procedures defined in [RFC5919] apply as-is to MT MP FEC element. This means that an mLDP speaker MAY signal its mLDP convergence using Typed Wildcard MP FEC element, and its MT mLDP convergence per topology using MT Typed Wildcard MP FEC element (as defined in earlier section). 7. Topology-Scoped Forwarding Since the MTID is part of the mLDP FEC, there is no need to support the concept of multiple topology tables in mLDP. Each MP LSP will be unique due to the MTID being part of the FEC. There is also no need to have specific Label Forwarding Tables per topology. Each MP LSP will have its own unique local label in the LFT. In order to satisfy the MTR in mLDP, the upstream LSR and downstream forwarding interface procedures must be changed. 7.1. Upstream LSR selection The procedures as described in draft-ietf-mpls-ldp-p2mp-15 section- 2.4.1.1 depend on the best path to reach the root. When the MTID is signaled as part of the FEC, the MTID is used to select the topology Wijnands, et. al Expires May 2012 [Page 8] Internet-Draft mLDP Extensions for Multi-Topology Routing November 2011 that must to be used to find the best path to the root address. Using the next-hop from this best path, a LDP peer is selected following the procedures as defined in draft-ietf-mpls-ldp-p2mp-15. 7.2. Downstream forwarding interface The procedures as described in draft-ietf-mpls-ldp-p2mp-15 section- 2.4.1.2 describe how a downstream forwarding interface is selected. In these procedures any interface leading to the downstream LDP neighbor can be considered as candidate forwarding interface. When the MTID is part of the FEC, this is no longer true. An interface must only be selected if it is part of the same topology that was signaled in the mLDP FEC element. Besides this restriction, the other procedures in draft-ietf-mpls-ldp-p2mp-15 section-2.4.1.2 apply. 8. Security Considerations This extension to mLDP does not introduce any new security considerations beyond that already apply to the base LDP specification [RFC5036], base mLDP specification [RFC6388], and MPLS security framework [RFC5920]. 9. IANA Considerations The document introduces following new protocol elements that require IANA consideration and code point assignment: o New LDP Capability TLV: "Multipoint MT Capability" TLV (requested code point: 0x50F from LDP registry "TLV Type Name Space") o New address families under IANA registry "Address Family Numbers": - MT IP: Multi-Topology IP version 4 (requested codepoint: 26) - MT IPv6: Multi-Topology IP version 6 (requested codepoint: 27) o New registry "LDP Multi-Topology (MT) ID Name Space" under "LDP Parameter" namespace. The registry is defined as: Range/Value Name ----------- ------------------------ 0 Default Topology 1-4095 Unassigned Wijnands, et. al Expires May 2012 [Page 9] Internet-Draft mLDP Extensions for Multi-Topology Routing November 2011 4096-65534 Reserved (for future allocation) 65535 Wildcard Topology 10. References 10.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC4915] P. Psenak, S. Mirtorabi, A. Roy, L. Nguyen, P. Pillay- Esnault, "Multi-Topology Routing in OSPF", RFC 4915, June 2007. [RFC5120] T. Przygienda, Z2 Sagl, N. Shen, N., "M-ISIS: Multi- Topology Routing in IS-IS", RFC 5120, February 2008. [MT-LDP] Q. Zhao, L. Fang, C. Zhou, L. Li, N. So, R. Torvi, "LDP Extension for Multiple Topology Support", draft-zhao-mpls- ldp-multi-topology-02, Work in progress, July 2011. [RFC6388] I. Minei, I. Wijnand, K. Kompella, B., "LDP Extensions for P2MP and MP2MP LSPs", RFC 6388, November 2011. 10.2. Informative References [RFC5036] L. Andersson, I. Minei, B. Thomas, "LDP Specification", RFC 5036, October 2007. [RFC5561] Thomas, B., Raza, K., Aggarwal, S., Aggarwal, R., and Le Roux, JL., "LDP Capabilities", RFC 5561, July 2009. [RFC5919] R. Asati, P. Mohapatra, E. Chen, B. Thomas, "Signaling LDP Label Advertisement Completion", RFC 5919, August 2010. [RFC5918] Asati, R., Minei, I., and Thomas, B. "Label Distribution Protocol Typed Wildcard FEC", RFC 5918, August 2010. [RFC5920] L. Fang, L. et al., "Security Framework for MPLS and GMPLS Networks", RFC 5920, July 2010. 11. Acknowledgments The authors would like to acknowledge Eric Rosen for his input on this specification. This document was prepared using 2-Word-v2.0.template.dot. Wijnands, et. al Expires May 2012 [Page 10] Internet-Draft mLDP Extensions for Multi-Topology Routing November 2011 Authors' Addresses IJsbrand Wijnand Cisco Systems, Inc. De kleetlaan 6a, Diegem 1831 Belgium. Email: ice@cisco.com Kamran Raza Cisco Systems, Inc. 2000 Innovation Drive, Ottawa, Ontario K2K-3E8, Canada. Email: skraza@cisco.com Wijnands, et. al Expires May 2012 [Page 11]