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Network Working Group K. KompellaRequest for Comments: 3480 Y. RekhterCategory: Standards Track Juniper Networks A. Kullberg NetPlane Systems February 2003Signalling Unnumbered Links in CR-LDP(Constraint-Routing Label Distribution Protocol)Status of this Memo This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.Copyright Notice Copyright (C) The Internet Society (2003). All Rights Reserved.Abstract Current signalling used by Multi-Protocol Label Switching Traffic Engineering (MPLS TE) does not provide support for unnumbered links. This document defines procedures and extensions to Constraint-Routing Label Distribution Protocol (CR-LDP), one of the MPLS TE signalling protocols that are needed in order to support unnumbered links.Specification of Requirements 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 inBCP 14,RFC 2119 [RFC2119].1. Overview Supporting MPLS TE over unnumbered links (i.e., links that do not have IP addresses) involves two components: (a) the ability to carry (TE) information about unnumbered links in IGP TE extensions (ISIS or OSPF), and (b) the ability to specify unnumbered links in MPLS TE signalling. The former is covered in [GMPLS-ISIS,GMPLS-OSPF]. The focus of this document is on the latter.Kompella, et al. Standards Track [Page 1]

RFC 3480         Signalling Unnumbered Links in CR-LDP     February 2003   Current signalling used by MPLS TE does not provide support for   unnumbered links because the current signalling does not provide a   way to indicate an unnumbered link in its Explicit Route Objects.   This document proposes simple procedures and extensions that allow   CR-LDP signalling [CR-LDP] to be used with unnumbered links.2. Link Identifiers   An unnumbered link has to be a point-to-point link.  An LSR at each   end of an unnumbered link assigns an identifier to that link.  This   identifier is a non-zero 32-bit number that is unique within the   scope of the LSR that assigns it.  If one is using OSPF or ISIS as   the IGP in support of traffic engineering, then the IS-IS and/or OSPF   and CR-LDP modules on an LSR must agree on the identifiers.   There is no a priori relationship between the identifiers assigned to   a link by the LSRs at each end of that link.   LSRs at the two end points of an unnumbered link exchange with each   other the identifiers they assign to the link.  Exchanging the   identifiers may be accomplished by configuration, by means of a   protocol such as LMP ([LMP]), by means of CR-LDP (especially in the   case where a link is a Forwarding Adjacency, see below), or by means   of IS-IS or OSPF extensions ([ISIS-GMPLS], [OSPF-GMPLS]).   Consider an (unnumbered) link between LSRs A and B.  LSR A chooses an   identifier for that link.  So does LSR B.  From A's perspective, we   refer to the identifier that A assigned to the link as the "link   local identifier" (or just "local identifier"), and to the identifier   that B assigned to the link as the "link remote identifier" (or just   "remote identifier").  Likewise, from B's perspective, the identifier   that B assigned to the link is the local identifier, and the   identifier that A assigned to the link is the remote identifier.   In the context of this document, the term "Router ID" means a stable   IP address of an LSR that is always reachable if there is any   connectivity to the LSR.  This is typically implemented as a   "loopback address"; the key attribute is that the address does not   become unusable if an interface on the LSR is down.  In some cases,   this value will need to be configured.  If one is using OSPF or ISIS   as the IGP in support of traffic engineering, then it is RECOMMENDED   for the Router ID to be set to the "Router Address" as defined in   [OSPF-TE], or "Traffic Engineering Router ID" as defined in [ISIS-   TE].   This section is equally applicable to the case of unnumbered   component links (see [LINK-BUNDLE]).Kompella, et al.            Standards Track                     [Page 2]

RFC 3480         Signalling Unnumbered Links in CR-LDP     February 20033. Unnumbered Forwarding Adjacencies   If an LSR that originates an LSP advertises this LSP as an unnumbered   Forwarding Adjacency in IS-IS or OSPF (see [LSP-HIER]), or the LSR   uses the Forwarding Adjacency formed by this LSP as an unnumbered   component link of a bundled link (see [LINK-BUNDLE]), the LSR MUST   allocate an identifier to that Forwarding Adjacency (just like for   any other unnumbered link).  Moreover, the REQUEST message used for   establishing the LSP that forms the Forwarding Adjacency MUST contain   an LSP_TUNNEL_INTERFACE_ID TLV (described below), with the LSR's   Router ID set to the head end's Router ID, and the Interface ID set   to the identifier that the LSR allocated to the Forwarding Adjacency.   If the REQUEST message contains the LSP_TUNNEL_INTERFACE_ID TLV, then   the tail-end LSR MUST allocate an identifier to that Forwarding   Adjacency (just like for any other unnumbered link).  Furthermore,   the MAPPING message for the LSP MUST contain an   LSP_TUNNEL_INTERFACE_ID TLV, with the LSR's Router ID set to the   tail-end's Router ID, and the Interface ID set to the identifier   allocated by the tail-end LSR.   For the purpose of processing the Explicit Route TLV and the   Interface ID TLV, an unnumbered Forwarding Adjacency is treated as an   unnumbered (TE) link or an unnumbered component link as follows.  The   LSR that originates the Adjacency sets the link local identifier for   that link to the value that the LSR allocates to that Forwarding   Adjacency, and the link remote identifier to the value carried in the   Interface ID field of the Reverse Interface ID TLV (for the   definition of Reverse Interface ID TLV see below).  The LSR that is a   tail-end of that Forwarding Adjacency sets the link local identifier   for that link to the value that the LSR allocates to that Forwarding   Adjacency, and the link remote identifier to the value carried in the   Interface ID field of the Forward Interface ID TLV (for the   definition of Forward Interface ID see below).Kompella, et al.            Standards Track                     [Page 3]

RFC 3480         Signalling Unnumbered Links in CR-LDP     February 20033.1. LSP_TUNNEL_INTERFACE_ID TLV   The LSP_TUNNEL_INTERFACE ID TLV has Type 0x0836 and length 8.  The   format is given below.   Figure 1: LSP_TUNNEL_INTERFACE_ID TLV    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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |0|0|            Type           |            Length             |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                        LSR's Router ID                        |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                    Interface ID (32 bits)                     |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   This TLV can optionally appear in either a REQUEST message or a   MAPPING message.  In the former case, we call it the "Forward   Interface ID" for that LSP; in the latter case, we call it the   "Reverse Interface ID" for the LSP.4. Signalling Unnumbered Links in Explicit Route TLV   A new Type of ER-Hop TLV of the Explicit Route TLV is used to specify   unnumbered links.  This Type is called Unnumbered Interface ID, and   has the following format:   The Type is 0x0837, and the Length is 12.  The L bit is set to   indicate a loose hop, and cleared to indicate a strict hop.   The Interface ID is the identifier assigned to the link by the LSR   specified by the router ID.   Figure 2: Unnumbered Interface ID    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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |0|0|          Type             |            Length = 12        |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |L|                         Reserved                            |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                           Router ID                           |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                     Interface ID (32 bits)                    |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+Kompella, et al.            Standards Track                     [Page 4]

RFC 3480         Signalling Unnumbered Links in CR-LDP     February 20034.1. Processing the IF_ID TLV   When an LSR receives a REQUEST message containing the IF_ID   (Interface ID) TLV (see [GMPLS-CRLDP]) with the IF_INDEX TLV, the LSR   processes this TLV as follows.  The LSR must have information about   the identifiers assigned by its neighbors to the unnumbered links   between the neighbors and the LSR.  The LSR uses this information to   find a link with tuple <Router ID, local identifier> matching the   tuple <IP Address, Interface ID> carried in the IF_INDEX TLV.  If the   matching tuple is found, the match identifies the link for which the   LSR has to perform label allocation.   Otherwise, the LSR SHOULD return an error.4.2. Processing the Unnumbered Interface ID ER-Hop TLV   The Unnumbered Interface ID ER-Hop is defined to be a part of a   particular abstract node if that node has the Router ID that is equal   to the Router ID field in the Unnumbered Interface ID ER-Hop, and if   the node has an (unnumbered) link or an (unnumbered) Forwarding   Adjacency whose local identifier (from that node's point of view) is   equal to the value carried in the Interface ID field of the   Unnumbered Interface ID ER-Hop.   With this in mind, the Explicit Route TLV processing in the presence   of the Unnumbered Interface ID ER-Hop follows the rules specified in   section 4.8.1 of [CR-LDP].   As part of the Explicit Route TLV processing, or to be more precise,   as part of the next hop selection, if the outgoing link is   unnumbered, the REQUEST message that the node sends to the next hop   MUST include the IF_ID TLV, with the IP address field of that TLV set   to the Router ID of the node, and the Interface ID field of that TLV   set to the identifier assigned to the link by the node.5. IANA ConsiderationsRFC 3036 [LDP] defines the LDP TLV name space.RFC 3212 [CD-LDP]   further subdivides the range of that TLV space for TLVs associated   with the CR-LDP in the range 0x0800 - 0x08FF, and defines the rules   for the assignment of TLVs within that range using the terminology ofBCP 26,RFC 2434, "Guidelines for Writing an IANA Considerations   Section in RFCs".  Those rules apply to the assignment of TLV Types   for the Unnumbered Interface ID and LSP_TUNNEL_INTERFACE_ID TLVs   defined in this document.Kompella, et al.            Standards Track                     [Page 5]

RFC 3480         Signalling Unnumbered Links in CR-LDP     February 20036. Security Considerations   This document extends CR-LDP and raises no new security issues.  CR-   LDP inherits the same security mechanism described in Section 4.0 of   [LDP] to protect against the introduction of spoofed TCP segments   into LDP session connection streams.7. Acknowledgments   Thanks to Rahul Aggarwal for his comments on the text.  Thanks also   to Bora Akyol, Vach Kompella, and George Swallow.8. References8.1. Normative References   [CR-LDP]      Jamoussi, B., Andersson, L., Callon, R., Dantu, R., Wu,                 L., Doolan, P., Worster, T., Feldman, N., Fredette, A.,                 Girish, M., Gray, E., Heinanen, J., Kilty, T. and A.                 Malis, "Constraint-Based LSP Setup using LDP",RFC3212, January 2002.   [GMPLS-SIG]   Berger, L., "Generalized Multi-Protocol Label Switching                 (GMPLS) Signaling Functional Description",RFC 3471,                 January 2003.   [GMPLS-CRLDP] Ashwood, P., Ed. and L. Berger, "Generalized Multi-                 Protocol Label Switching (GMPLS) Signaling Constraint-                 based Routed Label Distribution Protocol (CR-LDP)                 Extensions",RFC 3472 January 2003.   [LDP]         Andersson, L., Doolan, P., Feldman, N., Fredette, A.                 and B. Thomas, "LDP Specification",RFC 3036, January                 2001   [RFC2119]     Bradner, S., "Key words for use in RFCs to Indicate                 Requirement Levels",BCP 14,RFC 2119, March 1997.8.2. Informative References   [LINK-BUNDLE] Kompella, K., Rekhter, Y., and Berger, L., "Link                 Bundling in MPLS Traffic Engineering", Work in                 Progress.   [LSP-HIER]    Kompella, K., and Rekhter, Y., "LSP Hierarchy with MPLS                 TE", Work in Progress.Kompella, et al.            Standards Track                     [Page 6]

RFC 3480         Signalling Unnumbered Links in CR-LDP     February 2003   [LMP]         Lang, J., Mitra, K., et al., "Link Management Protocol                 (LMP)", Work in Progress.   [GMPLS-ISIS]  Kompella, K., Rekhter, Y., Banerjee, A. et al, "IS-IS                 Extensions in Support of Generalized MPLS", Work in                 Progress.   [GMPLS-OSPF]  Kompella, K., Rekhter, Y., Banerjee, A. et al, "OSPF                 Extensions in Support of Generalized MPLS", Work in                 Progress.   [OSPF-TE]     Katz, D., Yeung, D., Kompella, K., "Traffic Engineering                 Extensions to OSPF Version 2", Work in Progress.   [ISIS-TE]     Li, T., Smit, H., "IS-IS extensions for Traffic                 Engineering", Work in Progress.9. Authors' Addresses   Kireeti Kompella   Juniper Networks, Inc.   1194 N. Mathilda Ave.   Sunnyvale, CA 94089   EMail: kireeti@juniper.net   Yakov Rekhter   Juniper Networks, Inc.   1194 N. Mathilda Ave.   Sunnyvale, CA 94089   EMail: yakov@juniper.net   Alan Kullberg   NetPlane Systems, Inc.   Westwood Executive Center   200 Lowder Brook Drive   Westwood, MA  02090   EMail: akullber@netplane.comKompella, et al.            Standards Track                     [Page 7]

RFC 3480         Signalling Unnumbered Links in CR-LDP     February 200310.  Full Copyright Statement   Copyright (C) The Internet Society (2003).  All Rights Reserved.   This document and translations of it may be copied and furnished to   others, and derivative works that comment on or otherwise explain it   or assist in its implementation may be prepared, copied, published   and distributed, in whole or in part, without restriction of any   kind, provided that the above copyright notice and this paragraph are   included on all such copies and derivative works.  However, this   document itself may not be modified in any way, such as by removing   the copyright notice or references to the Internet Society or other   Internet organizations, except as needed for the purpose of   developing Internet standards in which case the procedures for   copyrights defined in the Internet Standards process must be   followed, or as required to translate it into languages other than   English.   The limited permissions granted above are perpetual and will not be   revoked by the Internet Society or its successors or assigns.   This document and the information contained herein is provided on an   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.Kompella, et al.            Standards Track                     [Page 8]

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