MPLS Working Group IJsbrand Wijnand Internet Draft Cisco Systems, Inc. Intended status: Standards Track Expires: January 1, 2013 Kamran Raza Cisco Systems, Inc. July 2, 2012 mLDP Extensions for Multi Topology Routing draft-iwijnand-mpls-mldp-multi-topology-02.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 January 1, 2013. Copyright 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 Wijnands, et. al Expires Jan 2013 [Page 1] Internet-Draft mLDP Extensions for Multi-Topology Routing July 2012 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 network, mLDP is also required to become topology-aware. This document specifies extensions to mLDP to support Multi-Topology Routing. Table of Contents 1. Glossary .......................................................... 3 2. Introduction ...................................................... 3 3. Conventions used in this document ................................. 3 4. MT-Scoped mLDP FECs ............................................... 4 4.1. MP FEC Extensions for MT ....................................... 4 4.1.1. MP FEC Element ............................................. 4 4.1.2. MT IP Address Families ..................................... 5 4.1.3. IP MT MP FEC Element ....................................... 5 4.2. Topology IDs ................................................... 6 5. Multipoint MT Capability .......................................... 6 6. MT Applicability on FEC-based features ............................ 7 6.1. MT Typed Wildcard MP FEC Elements .............................. 7 6.2. MT End-of-LIB .................................................. 8 7. Topology-Scoped Forwarding ........................................ 9 7.1. Upstream LSR selection ......................................... 9 7.2. Downstream forwarding interface selection ...................... 9 8. Security Considerations ........................................... 9 9. IANA Considerations ............................................... 9 10. References ...................................................... 10 10.1. Normative References ......................................... 10 10.2. Informative References ....................................... 10 11. Acknowledgments ................................................. 10 Wijnands, et. al Expires Jan 2013 [Page 2] Internet-Draft mLDP Extensions for Multi-Topology Routing July 2012 1. Glossary MT - Multi-Topology MT-ID - Multi-Topology Identifier MTR - Multi-Topology Routing IGP - Interior Gateway Protocol MP - Multipoint (P2MP or MP2MP) mLDP - Multipoint LDP P2MP - Point-to-Multipoint MP2MP - Multipoint-to-Multipoint FEC - Forwarding Equivalence Class 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 IGPs. To support IGP MT, similar LDP extensions [MT-LDP] have been proposed to make LDP MT-aware and be able to setup unicast Label Switched Paths (LSPs) along IGP MT routing paths. Multipoint 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 network 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). 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]. Wijnands, et. al Expires Jan 2013 [Page 3] Internet-Draft mLDP Extensions for Multi-Topology Routing July 2012 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. 4. MT-Scoped mLDP FECs As defined in [MT-LDP], the Multi-Topology Identifier (MT-ID) is an identifier that is used to associate an LSP with a certain MTR topology. In the context of MP LSPs, this identifier is part of the mLDP FEC encoding so that LDP peers are able to setup an MP LSP via their own defined MTR policy. In order to avoid conflicting MTR policies for the same mLDP FEC, the MT-ID needs to be a part of the FEC, so that different MT-ID values will result in unique MP-LSP FEC elements. Since the MT-ID is part of the FEC, it will apply to all the LDP messages that potentially include an mLDP FEC element. 4.1. MP FEC Extensions for MT Following subsections propose the extensions to bind an mLDP FEC to a topology. The mLDP MT extensions reuse some of the extensions specified in [MT-LDP]. 4.1.1. MP FEC Element Base mLDP specification [RFC6388] defines MP FEC Element 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 | Address Family | AF Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Root Node Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Opaque Length | Opaque Value ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: 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. Wijnands, et. al Expires Jan 2013 [Page 4] Internet-Draft mLDP Extensions for Multi-Topology Routing July 2012 To extend MP FEC elements for MT, the MT-ID is an identifier that is relevant in the context of the root address of the MP LSP. The MT-ID identifier determines in which topology the root address needs to be resolved. Since the MT-ID should be considered part of the mLDP FEC, the most natural place to encode the MT-ID is as part of the root address. To encode MT-ID as part of the root address, we are proposing to use "MT IP" Address Families as described in following sub section. 4.1.2. MT IP Address Families [MT-LDP] specification proposes new address families, named "MT IP" and "MT IPv6", to allow specification of an IP prefix within a topology scope. The Figure 2 of [MT-LDP] specification defines the format of the data associated with these new Address Families 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | (IP) Prefix | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | MT-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: MT IP Address Families Data Format [MT-LDP] Where "(IP) Prefix" is an IPv4 or IPv6 address corresponding to "MT IP" and "MT IPv6" address families respectively. 4.1.3. IP MT MP FEC Element We extend MP FEC Element for IP MT by using MT IP Address Family (and its associated MT-ID) in an MP FEC Element. The resultant MT MP FEC element will be encoded as follows: Wijnands, et. al Expires Jan 2013 [Page 5] Internet-Draft mLDP Extensions for Multi-Topology Routing July 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MP FEC type | AF (MT IP/ MT IPv6) | AF Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Root Node Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | MT-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Opaque Length | Opaque Value ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: IP MT-Scoped MP FEC Element Format In the context of this document, the applicable LDP FECs for MT mLDP include: o MP FEC Elements: o P2MP (type 0x6) o MP2MP-up (type 0x7) o MP2MP-down (type 0x8) o Typed Wildcard FEC Element (type 0x5) In case of "Typed Wildcard FEC Element", the sub FEC Element type 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. 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 Wijnands, et. al Expires Jan 2013 [Page 6] Internet-Draft mLDP Extensions for Multi-Topology Routing July 2012 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: 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 4: "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 Capability: 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: Set to 1 to announce and 0 to withdraw the capability (as per [RFC5561]). 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 4.1. ) 2. Topology-scoped mLDP forwarding setup ( Section 7. ) 6. MT Applicability on FEC-based features 6.1. MT Typed Wildcard MP FEC Elements [RFC5918] extends base LDP and defines Typed Wildcard FEC Element framework. Typed Wildcard FEC element can be used in any LDP Wijnands, et. al Expires Jan 2013 [Page 7] Internet-Draft mLDP Extensions for Multi-Topology Routing July 2012 message to specify a wildcard operation for the given type of FEC. The MT extensions proposed in document do not require any extension in procedures for Typed Wildcard FEC Element support [RFC5918], and these procedures apply as-is to Multipoint MT FEC wildcarding. Like Typed Wildcard MT Prefix FEC Element, as defined in [MT-LDP], the MT extensions allow use of "MT IP" or "MT IPv6" in the Address Family field of the Typed Wildcard MP FEC element in order to use wildcard operations for MP FECs in the context of a given topology as identified by the MT-ID field. This document proposes following format and encoding for a Typed Wildcard MP FEC element: 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.) | +-+-+-+-+-+-+-+-+ Figure 5: "Typed Wildcard MP FEC Element" for IP MT Where: Type: One of MP FEC Element type (P2MP, MP2MP-up, MP2MP-down). The proposed format allows an LSR to perform wildcard MP FEC operations under the scope of a topology. 6.2. MT End-of-LIB [RFC5919] specifies extensions and procedures that allows an LDP speaker to signal its End-of-LIB (i.e. convergence) for a given FEC type towards a peer. MT extensions for MP FEC do not require any change in these procedures and they apply as-is to MT MP FEC elements. This means that an MT mLDP speaker MAY signal its convergence per topology using a MT Typed Wildcard MP FEC element. Wijnands, et. al Expires Jan 2013 [Page 8] Internet-Draft mLDP Extensions for Multi-Topology Routing July 2012 7. Topology-Scoped Forwarding Since the MT-ID is part of an 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 MT-ID being part of the FEC. There is also no need to have specific label forwarding tables per topology, and each MP LSP will have its own unique local label in the table. However, in order to implement MTR in an mLDP environment, the selection procedures for upstream LSR and downstream forwarding interface need to be changed. 7.1. Upstream LSR selection The procedures as described in RFC-6388 section 2.4.1.1 depend on the best path to reach the root. When the MT-ID is signaled as part of the FEC, the MT-ID is used to select the topology that must 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 [RFC6388]. 7.2. Downstream forwarding interface selection The procedures as described in RFC-6388 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 MT-ID 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 [RFC6388] 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 element that requires IANA consideration and code point assignment: Wijnands, et. al Expires Jan 2013 [Page 9] Internet-Draft mLDP Extensions for Multi-Topology Routing July 2012 o New LDP Capability TLV: "Multipoint MT Capability" TLV (requested code point: 0x511 from LDP registry "TLV Type Name Space") 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 Extensions for Multi Topology Routing", draft-ietf-mpls- ldp-multi-topology-03, Work in progress, March 2012. [RFC6388] I. Minei, I. Wijnand, K. Kompella, B., "LDP Extensions for P2MP and MP2MP LSPs", RFC 6388, November 2011. [RFC5561] Thomas, B., Raza, K., Aggarwal, S., Aggarwal, R., and Le Roux, JL., "LDP Capabilities", RFC 5561, July 2009. 10.2. Informative References [RFC5036] L. Andersson, I. Minei, B. Thomas, "LDP Specification", RFC 5036, October 2007. [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 Jan 2013 [Page 10] Internet-Draft mLDP Extensions for Multi-Topology Routing July 2012 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 Jan 2013 [Page 11]