mLDP Extensions for Multi Topology Routing
Author(s): Kamran Raza, IJsbrand Wijnands
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....
MPLS Working Group IJsbrand Wijnands Internet Draft Cisco Systems, Inc. Intended status: Standards Track Expires: December 19, 2013 Kamran Raza Cisco Systems, Inc. June 20, 2013 mLDP Extensions for Multi Topology Routing draft-iwijnand-mpls-mldp-multi-topology-03.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 December 19, 2013. Copyright Notice Copyright (c) 2013 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 December 2013 [Page 1] Internet-Draft mLDP Extensions for Multi-Topology Routing June 2013 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 .......................... 4 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. MT MP FEC Element .............................. 6 4.2. Topology IDs .......................................... 7 5. MT Multipoint Capability .................................... 7 6. MT Applicability on FEC-based features ...................... 8 6.1. Typed Wildcard 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 selection .............. 9 8. LSP Ping Extensions ......................................... 9 9. Security Considerations .................................... 10 10. IANA Considerations ....................................... 10 11. References ................................................ 11 11.1. Normative References ................................ 11 11.2. Informative References .............................. 11 12. Acknowledgments ........................................... 12 Wijnands, et. al Expires December 2013 [Page 2] Internet-Draft mLDP Extensions for Multi-Topology Routing June 2013 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). Wijnands, et. al Expires December 2013 [Page 3] Internet-Draft mLDP Extensions for Multi-Topology Routing June 2013 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 [RFC 2119]. 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: Wijnands, et. al Expires December 2013 [Page 4] Internet-Draft mLDP Extensions for Multi-Topology Routing June 2013 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. 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] Wijnands, et. al Expires December 2013 [Page 5] Internet-Draft mLDP Extensions for Multi-Topology Routing June 2013 Where "(IP) Prefix" is an IPv4 or IPv6 address corresponding to "MT IP" and "MT IPv6" address families respectively. 4.1.3. MT MP FEC Element We extend MP FEC Element for 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: 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. Wijnands, et. al Expires December 2013 [Page 6] Internet-Draft mLDP Extensions for Multi-Topology Routing June 2013 4.2. Topology IDs This document assumes the same definitions and procedures associated with MT-ID as defined in [MT-LDP] specification. 5. MT Multipoint Capability "MT Multipoint 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: 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| MT Multipoint Cap.(IANA) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |S| Reserved | +-+-+-+-+-+-+-+-+ Figure 4: "MT Multipoint Capability" TLV Format Where: U- and F-bits: MUST be 1 and 0, respectively, as per Section 3 of LDP Capabilities [RFC5561]. MT Multipoint Capaility: 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 "MT Multipoint" capability MUST support the following: Wijnands, et. al Expires December 2013 [Page 7] Internet-Draft mLDP Extensions for Multi-Topology Routing June 2013 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. 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 message to specify a wildcard operation for a 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 MT MP FEC Element" Where: Type: One of MP FEC Element type (P2MP, MP2MPup, MP2MP-down). 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 that allows an LDP speaker to signal its End-of-LIB (i.e. convergence) for a given FEC Wijnands, et. al Expires December 2013 [Page 8] Internet-Draft mLDP Extensions for Multi-Topology Routing June 2013 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 MT Typed Wildcard MP FEC element. 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 network, the selection procedures for upstream LSR and downstream forwarding interface need be changed. 7.1. Upstream LSR selection The procedures as described in RFC6388 section-184.108.40.206 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 RFC6388 section-220.127.116.11 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. LSP Ping Extensions [RFC6425] defines procedures to detect data plane failures in Multipoint MPLS LSPs. Section 3.1.2 of [RFC6425] defines new Sub- Types and Sub-TLVs for Multipoint LDP FECs to be sent in "Target FEC Stack" TLV of an MPLS echo request message [RFC4379]. To support LSP ping for MT Multipoint LSPs, this document uses existing sub-types "P2MP LDP FEC Stack" and "MP2MP LDP FEC Stack" defined in [RFC6425]. The proposed extension is to specify "MT IP" or "MT IPv6" in the "Address Family" field, set the "Address Length" Wijnands, et. al Expires December 2013 [Page 9] Internet-Draft mLDP Extensions for Multi-Topology Routing June 2013 field to 8 (for MT IP) or 20 (for MT IPv6), and encode the sub-TLV with additional MT-ID information as an extension to the "Root LSR Address" field. The resultant format of sub-tlv 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Address Family (MT IP/MT IPv6) | Address Length| | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ~ Root LSR Address (Cont.) ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | MT-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Opaque Length | Opaque Value ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + ~ ~ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 6: Multipoint LDP FEC Stack Sub-TLV Format for MT The rules and procedures of using this new sub-TLV in an MPLS echo request message are same as defined for P2MP/MP2MP LDP FEC Stack Sub-TLV in [RFC6425] with only difference being that Root LSR address is now topology scoped. 9. 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]. 10. IANA Considerations This document defines a new LDP capability parameter TLV. IANA is requested to assign the lowest available value after 0x0500 from "TLV Type Name Space" in the "Label Distribution Protocol (LDP) Parameters" registry within "Label Distribution Protocol (LDP) Name Spaces" as the new code point for the LDP TLV code point. Wijnands, et. al Expires December 2013 [Page 10] Internet-Draft mLDP Extensions for Multi-Topology Routing June 2013 +-----+------------------+---------------+-------------------------+ |Value| Description | Reference | Notes/Registration Date | +-----+------------------+---------------+-------------------------+ | TBA | MT Multipoint | This document | | | | Capability | | | +-----+------------------+---------------+-------------------------+ 11. References 11.1. Normative References [RFC 2119] S. Bradner, "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", RFC4915, June 2007. [RFC5120] T. Przygienda, Z2 Sagl, N. Shen, N. Sheth, "M-ISIS: Multi- Topology Routing in IS-IS", RFC5120, February 2008. [MT-LDP] Q. Zhao, L. Fang, C. Zhou, L. Li, K. Raza, "LDP Extensions for Multiple Topology Routing", draft-ietf-mpls-ldp-multi- topology-08, Work in progress, May 2013. [RFC6388] I. Minei, I. Wijnands, K. Kompella, B. Thomas, "LDP Extensions for P2MP and MP2MP LSPs", RFC6388, November 2011. [RFC4379] S. Sexana, G. Swallow, Z. Ali, A. Farrel, S. Yasukawa, T. Nadeau, "Detecting Multi-Protocol Label Switched (MPLS) Data Plane Failures", RFC4379, February 2006. [RFC6425] Kompella, K. and G. Swallow, "Detecting Data-Plane Failures in Point-to-Multipoint MPLS - Extensions to LSP Ping", RFC6425, November 2011. 11.2. Informative References [RFC5036] L. Andersson, I. Minei, B. Thomas, "LDP Specification", RFC5036, October 2007. [RFC5919] R. Asati, P. Mohapatra, E. Chen, B. Thomas, "Signaling LDP Label Advertisement Completion", RFC5919, August 2010. [RFC5918] R. Asati, I. Minei, B. Thomas, "Label Distribution Protocol Typed Wildcard FEC", RFC5918, August 2010. Wijnands, et. al Expires December 2013 [Page 11] Internet-Draft mLDP Extensions for Multi-Topology Routing June 2013 [RFC5920] L. Fang, et al., "Security Framework for MPLS and GMPLS Networks", RFC5920, July 2010. [RFC5561] B. Thomas, K. Raza, S. Aggarwal, R. Aggarwal, JL. Le Roux, "LDP Capabilities", RFC5561, July 2009. 12. 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. Authors' Addresses IJsbrand Wijnands Cisco Systems, Inc. De kleetlaan 6a, Diegem 1831 Belgium. Email: email@example.com Kamran Raza Cisco Systems, Inc. 2000 Innovation Drive, Kanata, Ontario K2K-3E8, Canada. Email: firstname.lastname@example.org Wijnands, et. al Expires December 2013 [Page 12]