Internet Engineering Task Force Q. Zhao Internet-Draft Huawei Technology Intended status: Standards Track L. Fang Expires: April 18, 2014 C. Zhou Cisco Systems L. Li China Mobile K. Raza Cisco Systems October 14, 2013 LDP Extensions for Multi Topology Routing draft-ietf-mpls-ldp-multi-topology-09.txt Abstract Multi-Topology (MT) routing is supported in IP networks with the use of MT aware IGPs. In order to provide MT routing within Multiprotocol Label Switching (MPLS) Label Distribution Protocol (LDP) networks new extensions are required. This document describes the LDP protocol extensions required to support MT routing in an MPLS environment. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on April 20, 2014. 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 Zhao, et al. Expires April 20, 2014 [Page 1] Internet-Draft LDP Multi Topology Extensions October 2013 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. Zhao, et al. Expires April 20, 2014 [Page 2] Internet-Draft LDP Multi Topology Extensions October 2013 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Signaling Extensions . . . . . . . . . . . . . . . . . . . . . 5 3.1. Topology-Scoped Forwarding Equivalence Class (FEC) . . . . 5 3.2. New Address Families: MT IP . . . . . . . . . . . . . . . 5 3.3. LDP FEC Elements with MT IP AF . . . . . . . . . . . . . . 6 3.4. IGP MT-ID Mapping and Translation . . . . . . . . . . . . 7 3.5. LDP MT Capability Advertisement . . . . . . . . . . . . . 7 3.5.1. Protocol Extension . . . . . . . . . . . . . . . . . . 7 3.5.2. Procedures . . . . . . . . . . . . . . . . . . . . . . 9 3.6. LDP Sessions . . . . . . . . . . . . . . . . . . . . . . . 10 3.7. Reserved MT ID Values . . . . . . . . . . . . . . . . . . 10 4. MT Applicability on FEC-based features . . . . . . . . . . . . 10 4.1. Typed Wildcard FEC Element . . . . . . . . . . . . . . . . 10 4.2. End-of-LIB . . . . . . . . . . . . . . . . . . . . . . . . 11 4.3. LSP Ping . . . . . . . . . . . . . . . . . . . . . . . . . 11 4.3.1. New FEC Sub-Types . . . . . . . . . . . . . . . . . . 11 4.3.2. MT LDP IPv4 FEC Sub-TLV . . . . . . . . . . . . . . . 12 4.3.3. MT LDP IPv6 FEC Sub-TLV . . . . . . . . . . . . . . . 12 4.3.4. Operation Considerations . . . . . . . . . . . . . . . 13 5. Error Handling . . . . . . . . . . . . . . . . . . . . . . . . 13 5.1. MT Error Notification for Invalid Topology ID . . . . . . 13 6. Backwards Compatibility . . . . . . . . . . . . . . . . . . . 13 7. MPLS Forwarding in MT . . . . . . . . . . . . . . . . . . . . 14 8. Security Consideration . . . . . . . . . . . . . . . . . . . . 14 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 10. Manageability Considerations . . . . . . . . . . . . . . . . . 16 10.1. Control of Function and Policy . . . . . . . . . . . . . . 16 10.2. Information and Data Models . . . . . . . . . . . . . . . 16 10.3. Liveness Detection and Monitoring . . . . . . . . . . . . 16 10.4. Verify Correct Operations . . . . . . . . . . . . . . . . 16 10.5. Requirements On Other Protocols . . . . . . . . . . . . . 16 10.6. Impact On Network Operations . . . . . . . . . . . . . . . 16 11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 16 12. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 18 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18 13.1. Normative References . . . . . . . . . . . . . . . . . . . 18 13.2. Informative References . . . . . . . . . . . . . . . . . . 19 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19 Zhao, et al. Expires April 20, 2014 [Page 3] Internet-Draft LDP Multi Topology Extensions October 2013 1. Introduction Multi-Topology (MT) routing is supported in IP networks with the use of MT aware IGPs. It would be advantageous for communications Service Providers (CSP) to support Multiple Topologies (MT) within MPLS environments (MPLS-MT). The benefits of MPLS-MT enabled networks include: o A CSP may want to assign varying Quality of Service (QoS) profiles to traffic, based on a specific MT. o Separate routing and MPLS domains may be used to isolated multicast and IPv6 islands within the backbone network. o Specific IP address space could be routed across an MT based on security or operational isolation requirements. o Low latency links could be assigned to an MT for delay sensitive traffic. o Management traffic could be separated from customer traffic using multiple MTs, where the management traffic MT does not use links that carries customer traffic. This document describes the Label Distribution Protocol (LDP) procedures and protocol extensions required to support MT routing in an MPLS environment. This document also updates RFC4379 by defining two new FEC types for Label Switched Path (LSP) ping. 2. Terminology This document uses MPLS terminology defined in [RFC5036]. Additional terms are defined below: o MT-ID: A 16 bit value used to represent the Multi-Topology ID. o Default MT Topology: A topology that is built using the MT-ID default value of 0. o MT Topology: A topology that is built using the corresponding MT-ID. 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]. Zhao, et al. Expires April 20, 2014 [Page 4] Internet-Draft LDP Multi Topology Extensions October 2013 3. Signaling Extensions 3.1. Topology-Scoped Forwarding Equivalence Class (FEC) LDP assigns and binds a label to a Forwarding Equivalence Class (FEC), where a FEC is a list of one of more FEC elements. To setup LSPs for unicast IP routing paths, LDP assigns local labels for IP prefixes, and advertises these labels to its peers so that an LSP is setup along the routing path. To setup MT LSPs for IP prefixes under a given topology scope, the LDP "prefix-related" FEC element must be extended to include topology information. This implies that MT-ID becomes an attribute of Prefix-related FEC element, and all FEC-Label binding operations are performed under the context of given topology (MT-ID). The following Subsection 3.2(New Address Families (AF): MT IP) defines the extension required to bind "prefix-related" FEC to a topology. 3.2. New Address Families: MT IP The LDP base specification [RFC5036] (Section 4.1) defines the "Prefix" FEC Element. The "Prefix" encoding is defined for a given "Address Family" (AF), and has length (in bits) specified by the "PreLen" field. To extend IP address families for MT, two new Address Families named "MT IP" and "MT IPv6" are used to specify IPv4 and IPv6 prefixes within a topology scope. The format of data associated with these new Address Families are described below: 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 Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | MT-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: MT IP Address Family Format Where "IP Address" is an IPv4 and IPv6 address/prefix for "MT IP" and "MT IPv6" AF respectively, and the field "MT-ID" corresponds to 16- bit Topology ID for given address. Zhao, et al. Expires April 20, 2014 [Page 5] Internet-Draft LDP Multi Topology Extensions October 2013 Where 16-bit "MT-ID" field defines the Topology ID, and the definition and usage of the rest fields in the FEC Elements are same as defined for IP/IPv6 AF. The value of MT-ID 0 corresponds to default topology and MUST be ignored on receipt so as to not cause any conflict/confusion with existing non-MT procedures. The defined FEC Elements with "MT IP" Address Family can be used in any LDP message and procedures that currently specify and allow the use of FEC Elements with IP/IPv6 Address Family. 3.3. LDP FEC Elements with MT IP AF The following section specifies the format extensions of the existing LDP FEC Elements. The "Address Family" of these FEC elements will be set to "MT IP" or "MT IPv6". The MT Prefix FEC element encoding 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Prefix (2) | Address Family (MT IP/MT IPv6)| PreLen | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Prefix | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | MT-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: MT Prefix FEC Element Format Similarly, the MT mLDP FEC elements encoding is as follows, where the mLDP FEC Type can be P2MP(6), MP2MP-up(7), and MP2MP-down(8): Zhao, et al. Expires April 20, 2014 [Page 6] Internet-Draft LDP Multi Topology Extensions October 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | mLDP FEC Type | Address Family (MT IP/MT IPv6)| Address Length| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ Root Node Address ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | MT-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Opaque Length | Opaque Value ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + ~ ~ | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: MT mLDP FEC Element Format The MT Typed Wildcard FEC element encoding 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Typed Wcard (5)| FEC Type | Len = 6 | AF = MT IP ..| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |... or MT IPv6 | MT ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4: MT Typed Wildcard FEC Element 3.4. IGP MT-ID Mapping and Translation The non-reserved non-special IGP MT-ID values can be used and carried in LDP without the need for translation. However, there is a need for translating reserved or special IGP MT-ID values to corresponding LDP MT-IDs. The corresponding special and reserved LDP MT-ID values are requested In Section 9. (IANA Considerations). 3.5. LDP MT Capability Advertisement 3.5.1. Protocol Extension We specify a new LDP capability, named "Multi-Topology (MT)", which is defined in accordance with LDP Capability definition guidelines [RFC5561]. The LDP "MT" capability can be advertised by an LDP speaker to its peers either during the LDP session initialization or Zhao, et al. Expires April 20, 2014 [Page 7] Internet-Draft LDP Multi Topology Extensions October 2013 after the LDP session is setup to announce LSR capability to support MT for the given IP address family. An LDP speaker MUST NOT send an MT AF unless the peer has said it can handle it. The MT capability is specified using "Multi-Topology Capability" TLV. The "Multi-Topology Capability" TLV format is in accordance with LDP capability guidelines as defined in [RFC5561]. To be able to specify IP address family, the capability specific data (i.e. "Capability Data" field of Capability TLV) is populated using "Typed Wildcard FEC Element" as defined in [RFC5918]. The format of "Multi-Topology Capability" 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |U|F| Multi-Topology Cap.(IANA) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |S| Reserved | | +-+-+-+-+-+-+-+-+ | ~ Typed Wildcard FEC element(s) ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 5: Multi-Topology Capability TLV Format Where: o U- and F-bits: MUST be 1 and 0, respectively, as per Section 3. (Signaling Extensions) of LDP Capabilities [RFC5561]. o Multi-Topology Capability: Capability TLV type (IANA assigned) o 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. o Typed Wildcard FEC element(s): One or more elements specified as the "Capability data". o Length: length of Value field, starting from S bit, in octets. o The encoding of Typed Wildcard FEC element, as defined in [RFC5918], is defined in the section 3.3 (Typed Wildcard FEC Element) of this document. In the case that the LDP initialization message can not hold all the MTs to be advertised, dynamic "Capability" message to advertise the Zhao, et al. Expires April 20, 2014 [Page 8] Internet-Draft LDP Multi Topology Extensions October 2013 capability" must be supported. 3.5.2. Procedures To announce its MT capability for an IP address family, LDP FEC type, and Multi Topology, an LDP speaker an LDP speaker sends an "MT Capability" including the exact Typed Wildcard FEC element with corresponding "AddressFamily" field (i.e., set to "MT IP" for IPv4 and set to "MT IPv6" for IPv6 address family), corresponding "FEC Type" field (i.e., set to "P2P", "P2MP", "MP2MP"), and corresponding "MT-ID". To announce its MT capability for both IPv4 and IPv6 address family, or for multiple FEC types, or for multiple Multi Topologies, an LDP speaker an LDP speaker sends "MT Capability" with one or more MT Typed FEC elements in it. o The capability for supporting multi-topology in LDP can be advertised during LDP session initialization stage by including the LDP MT capability TLV in LDP Initialization message. After an LDP session is established, the MT capability can also be advertised or withdrawn using Capability message (only if "Dynamic Announcement" capability [RFC5561] has already been successfully negotiated). o If an LSR has not advertised MT capability, its peer MUST NOT send label mapping messages that include MT identifier to this LSR. o If an LSR receives a Label Mapping message with an MT parameter from downstream LSR-D and its upstream LSR-U has not advertised MT capability, an LSP for the MT will not be established. o If an LSR is changed from non-MT capable to MT capable, it sets the S bit in MT capability TLV and advertises via the Capability message. The existing LSP is treated as LSP for default MT (ID 0). o If an LSR is changed from LDP-MT capable to non-MT capable, it initiates withdraw of all label mapping for existing LSPs of all non-default MTs. It also cleanup all the LSPs of all non-default MTs locally. Then it clears the S bit in MT capability TLV and advertises via the Capability message. When an LSR knows the peer node is changed from LDP-MT capable to non-MT capable, it cleanup all the LSPs of all non-default MTs locally and initiate withdraw of all label mapping for existing LSPs of all non-default MTs. Both sides of the nodes send label release to its peer once they receive the label release messages even both sides have already cleaned up all the LSPs locally. Zhao, et al. Expires April 20, 2014 [Page 9] Internet-Draft LDP Multi Topology Extensions October 2013 o If an LSR is changed from IGP-MT capable to non-MT capable, it may wait until the routes update to withdraw FEC and release the label mapping for existing LSPs of specific MT. 3.6. LDP Sessions Since using different label spaces for different topologies would imply significant changes to the data plane, a single global label space is supported in this solution. There will be one session supported for each pair of peer, even there are multiple topologies supported between these two peers. 3.7. Reserved MT ID Values Certain MT topologies are assigned to serve predetermined purposes. In Section 9. (IANA Considerations), this document defines a new IANA registry "LDP Multi-Topology ID Name Space" under IANA "LDP Parameter" namespace to keep an LDP MT-ID reserved value. If an LSR receives a FEC element with an "MT-ID" value that is "Reserved" for future use (and not IANA allocated yet), the LSR must abort the processing of the FEC element, and SHOULD send a notification message with status code "Invalid MT-ID" to the sender. 4. MT Applicability on FEC-based features 4.1. Typed Wildcard FEC Element [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/action for given type of FEC. The MT extensions defined in document do not require any extension to procedures for Typed Wildcard FEC element, and these procedures apply as-is to MT 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 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. The defined format in Section 3.3 (Typed Wildcard FEC Element) allows an LSR to perform wildcard FEC operations under the scope of a topology. If an LSR wishes to perform wildcard operation that applies to all topologies, it can use a "Wildcard Topology" MT-ID. For example, upon local configuration of topology "x", an LSR may send a wildcard label withdraw request with MT-ID "x" to withdraw all Zhao, et al. Expires April 20, 2014 [Page 10] Internet-Draft LDP Multi Topology Extensions October 2013 its labels from the peer that advertised under the scope of topology "x". Additionally, upon a global configuration change, an LSR may send a wildcard label withdraw with the MT-ID set to "Wildcard Topology" to withdraw all its labels under all topologies from the peer. 4.2. End-of-LIB [RFC5919] specifies extensions and procedures for an LDP speaker to signal its convergence for a given FEC type towards a peer. The procedures defined in [RFC5919] applies as-is to an MT FEC element. This allows an LDP speaker to signal its IP convergence using Typed Wildcard FEC element, and its MT IP convergence per topology using a MT Typed Wildcard FEC element. 4.3. LSP Ping [RFC4379] defines procedures to detect data-plane failures in MPLS LSPs via LSP ping. That specification defines a "Target FEC Stack" TLV that describes the FEC stack being tested. This TLV is sent in an MPLS echo request message towards LSPs egress LSR, and is forwarded along the same data path as other packets belonging to the FEC. "Target FEC Stack" TLV contains one or more sub-TLVs pertaining to different FEC types. Section 3.2 of [RFC4379] defines Sub-Types and format for the FEC. To support LSP ping for MT LDP LSPs, this document defines following extensions to [RFC4379]. 4.3.1. New FEC Sub-Types We define two new FEC types for LSP ping: o MT LDP IPv4 FEC o MT LDP IPv6 FEC We also define following new sub-types for sub-TLVs to specify these FECs in the "Target FEC Stack" TLV of [RFC4379]: Sub-Type Length Value Field -------- ------ ----------------- TBA5 8 MT LDP IPv4 prefix TBA6 20 MT LDP IPv6 prefix Figure 6: new sub-types for sub-TLVs Zhao, et al. Expires April 20, 2014 [Page 11] Internet-Draft LDP Multi Topology Extensions October 2013 The rules and procedures of using these sub-TLVs in an MPLS echo request message are same as defined for LDP IPv4/IPv6 FEC sub-TLV types in [RFC4379]. 4.3.2. MT LDP IPv4 FEC Sub-TLV The format of "MT LDP IPv4 FEC" sub-TLV to be used in a "Target FEC Stack" [RFC4379] 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = TBA5(MT LDP IPv4 FEC) | Length = 8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv4 prefix | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Prefix Length | MBZ | MT-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 7: MT LDP IPv4 FEC sub-TLV The format of this sub-TLV is similar to LDP IPv4 FEC sub-TLV as defined in [RFC4379]. In addition to "IPv4 prefix" and "Prefix Length" fields, this new sub-TLV also specifies MT-ID (Multi-Topology ID). The Length for this sub-TLV is 5. 4.3.3. MT LDP IPv6 FEC Sub-TLV The format of "MT LDP IPv6 FEC" sub-TLV to be used in a "Target FEC Stack" [RFC4379] 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = TBA6(MT LDP IPv6 FEC) | Length = 20 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | IPv6 prefix | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Prefix Length | MBZ | MT-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 8: MT LDP IPv6 FEC sub-TLV The format of this sub-TLV is similar to LDP IPv6 FEC sub-TLV as Zhao, et al. Expires April 20, 2014 [Page 12] Internet-Draft LDP Multi Topology Extensions October 2013 defined in [RFC4379]. In addition to "IPv6 prefix" and "Prefix Length" fields, this new sub-TLV also specifies MT-ID (Multi-Topology ID). The Length for this sub-TLV is 17. 4.3.4. Operation Considerations To detect data plane failures using LSP Ping for a specific topology, the router will initiate an LSP Ping request with the target FEC stack TLV containing LDP MT IP Prefix Sub-TLV in the Echo Request packet. The Echo Request packet is sent with the label bound to the IP Prefix in the topology. Once the echo request packet reaches the target router, it will process the packet and perform checks for the LDP MT IP Prefix sub-TLV present in the Target FEC Stack as described in [RFC4379] and respond according to [RFC4379] processing rules. For the case that the LSP ping with return path not specified , the reply packet must go through the default topology instead of the topology where the Echo Request goes through. 5. Error Handling The extensions defined in this document utilize the existing LDP error handling defined in [RFC5036]. If an LSR receives an error notification from a peer for a session, it terminates the LDP session by closing the TCP transport connection for the session and discarding all MT-ID label mappings learned via the session. 5.1. MT Error Notification for Invalid Topology ID If an LSR has advertised an MT Capability TLV using the Initialization message or Capability message, which includes Typed Wildcard FEC elements with specific MT-IDs, and it receives an MT message with a MT-ID which is not included in the supported list, it should response this "Invalid Topology ID" status code. 6. Backwards Compatibility The MPLS-MT solution is backwards compatible with existing LDP enhancements defined in [RFC5036], including message authenticity, integrity of message, and topology loop detection. The legacy node which does not support MT should not receive any MT related LDP messages. In case the bad things does happen, according to [RFC5036], processing of such message should be aborted. Zhao, et al. Expires April 20, 2014 [Page 13] Internet-Draft LDP Multi Topology Extensions October 2013 7. MPLS Forwarding in MT Although forwarding is out of the scope of this draft, we include some forwarding consideration for informational purpose here. The specified signaling mechanisms allow all the topologies to share the platform-specific label space; this is the feature that allows the existing data plane techniques to be used; and there is no way for the data plane to associate a received packet with any one topology, meaning that topology-specific label spaces cannot be used. 8. Security Consideration No specific security issues with the defined solutions are known. The defined extensions in this document do not introduce any new security considerations beyond that already apply to the base LDP specification [RFC5036] and [RFC5920]. 9. IANA Considerations The document introduces following new protocol elements that require IANA consideration and assignments: o New LDP Capability TLV: "Multi-Topology Capability" TLV (requested code point: TBA1 from LDP registry "TLV Type Name Space"). o New Status Code: "Multi-Topology Capability not supported" (requested code point: TBA2 from LDP registry "Status Code Name Space"). This status code is only used by node that supports MT when decided to withdraw this capability. o New Status Code: "Invalid Topology ID" (requested code point: TBA3 from LDP registry "Status Code Name Space"). Registry: Range/Value Description -------------- ------------------------------ TBA1 Multi-Topology Capability TBA2 Multi-Topology Capability not supported TBA3 Invalid Topology ID Zhao, et al. Expires April 20, 2014 [Page 14] Internet-Draft LDP Multi Topology Extensions October 2013 Figure 9: New Code Points for LDP Multi Topology Extensions 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) Figure 10: Address Family Numbers o New registry "LDP Multi-Topology (MT) ID Name Space" under "LDP Parameter" namespace. The allocation policies for this registry are: Range/Value Purpose Reference ----------- ------------------------------------- --------- 0 Default/standard topology 1 IPv4 in-band management 2 IPv6 routing topology 3 IPv4 multicast topology 4 IPv6 multicast topology 5 IPv6 in-band management 6-3995 Reserved for future IGP topologies 3996-4095 Reserved for IGP experimental topologies 4096-4127 Reserved for LDP topologies 4128-65534 Reserved for LDP experimental topologies 65535 Wildcard Topology Figure 11: LDP Multi-Topology (MT) ID Name Space o New Sub-TLV Types for LSP ping: Following new sub-type values under TLV type 1 (Target FEC Stack) from "Multi-Protocol Label Switching (MPLS) Label Switched Paths (LSPs) Ping Parameters" registry, and "TLVs and sub-TLVs" sub-registry. Sub-Type Value Field -------- ----------- TBA4 MT LDP IPv4 prefix TBA5 MT LDP IPv6 prefix Figure 12: New Sub-TLV Types for LSP ping Zhao, et al. Expires April 20, 2014 [Page 15] Internet-Draft LDP Multi Topology Extensions October 2013 IANA should allocate the next available numbers for these TBAs. 10. Manageability Considerations 10.1. Control of Function and Policy There are capabilities that should be configurable to enable good manageability. One such example is to allow enable or disable LDP Multi-Topology capability. It is assumed that the mapping of the LDP MT ID and IGP MT ID is manually configured on every router by default. If an automatic mapping between IGP MT IDs and LDP MT IDs is needed, there must be explicit configuration to do so. 10.2. Information and Data Models draft-li-mpls-ldp-mt-mib.txt describes the PCEP MIB, there is no new MIB Objects for this document. 10.3. Liveness Detection and Monitoring Mechanisms defined in this document do not imply any new liveness detection and monitoring requirements. 10.4. Verify Correct Operations If an operator is trying to debug LDP MT enabled network and wants to make the association between the LDP label advertisement and the IGP routing advertisement, then the user must understand the mapping mechanism to convert the IGP MT ID to the LDP MT ID. This type of mapping mechanisms is out of the scope of this document. 10.5. Requirements On Other Protocols If the LDP MT ID has an implicit dependency on IGP MT ID, then the corresponding IGP MT feature/s need to be supported. 10.6. Impact On Network Operations Mechanisms defined in this document do not have any impact on network operations. 11. Contributors Ning So Tata Communications Zhao, et al. Expires April 20, 2014 [Page 16] Internet-Draft LDP Multi Topology Extensions October 2013 2613 Fairbourne Cir. Plano, TX 75082 USA Email: ning.so@tatacommunications.com Raveendra Torvi Juniper Networks 10, Technoogy Park Drive Westford, MA 01886-3140 US Email: rtorvi@juniper.net Huaimo Chen Huawei Technology 125 Nagog Technology Park Acton, MA 01719 US Email: huaimochen@huawei.com Emily Chen 2717 Seville Blvd, Apt 1205, Clearwater, FL 33764 US Email: emily.chen220@gmail.com Chen Li China Mobile 53A, Xibianmennei Ave. Xunwu District, Beijing 01719 China Email: lichenyj@chinamobile.com Lu Huang China Mobile 53A, Xibianmennei Ave. Xunwu District, Beijing 01719 China Email: huanglu@chinamobile.com Daniel King Old Dog Consulting Zhao, et al. Expires April 20, 2014 [Page 17] Internet-Draft LDP Multi Topology Extensions October 2013 Email: E-mail: daniel@olddog.co.uk Zhenbin Li Huawei Technology 2330 Central Expressway Santa Clara, CA 95050 US Email: zhenbin.li@huawei.com 12. Acknowledgement The authors would like to thank Dan Tappan, Nabil Bitar, Huang Xin, Eric Rosen, IJsbrand Wijnands, Dimitri Papadimitriou, Yiqun Chai,pranjal Dutta, George Swallow, Curtis Villamizar, Adrian Farrel, Alia Atlas and Loa Anderson for their valuable comments on this draft. 13. References 13.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC4379] Kompella, K. and G. Swallow, "Detecting Multi-Protocol Label Switched (MPLS) Data Plane Failures", RFC 4379, February 2006. [RFC5036] Andersson, L., Minei, I., and B. Thomas, "LDP Specification", RFC 5036, October 2007. [RFC5561] Thomas, B., Raza, K., Aggarwal, S., Aggarwal, R., and JL. Le Roux, "LDP Capabilities", RFC 5561, July 2009. [RFC5918] Asati, R., Minei, I., and B. Thomas, "Label Distribution Protocol (LDP) 'Typed Wildcard' Forward Equivalence Class (FEC)", RFC 5918, August 2010. [RFC5919] Asati, R., Mohapatra, P., Chen, E., and B. Thomas, "Signaling LDP Label Advertisement Completion", RFC 5919, August 2010. Zhao, et al. Expires April 20, 2014 [Page 18] Internet-Draft LDP Multi Topology Extensions October 2013 13.2. Informative References [RFC5920] Fang, L., "Security Framework for MPLS and GMPLS Networks", RFC 5920, July 2010. Authors' Addresses Quintin Zhao Huawei Technology 125 Nagog Technology Park Acton, MA 01719 US Email: quintin.zhao@huawei.com Luyuan Fang Cisco Systems 300 Beaver Brook Road Boxborough, MA 01719 US Email: lufang@cisco.com Chao Zhou Cisco Systems 300 Beaver Brook Road Boxborough, MA 01719 US Email: czhou@cisco.com Lianyuan Li China Mobile 53A, Xibianmennei Ave. Xunwu District, Beijing 01719 China Email: lilianyuan@chinamobile.com Zhao, et al. Expires April 20, 2014 [Page 19] Internet-Draft LDP Multi Topology Extensions October 2013 Kamran Raza Cisco Systems 2000 Innovation Drive Kanata, ON K2K-3E8, MA Canada Email: E-mail: skraza@cisco.com Zhao, et al. Expires April 20, 2014 [Page 20]