Network Working Group Kireeti Kompella Internet Draft Juniper Networks Expiration Date: December 2002 Yakov Rekhter Juniper Networks Alan Kullberg NetPlane Systems Signalling Unnumbered Links in CR-LDP draft-ietf-mpls-crldp-unnum-06.txt 1. Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. 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. 2. Abstract Current signalling used by MPLS TE doesn't provide support for unnumbered links. This document defines procedures and extensions to CR-LDP, one of the MPLS TE signalling protocols, that are needed in order to support unnumbered links. draft-ietf-mpls-crldp-unnum-06.txt [Page 1] Internet Draft draft-ietf-mpls-crldp-unnum-06.txt May 2002 3. 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. Current signalling used by MPLS TE doesn't provide support for unnumbered links because the current signalling doesn't 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. 4. 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. The IS-IS and/or OSPF and RSVP 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 RSVP/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 idenfitier for that link. So is 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. This section is equally applicable to the case of unnumbered component links (see [LINK-BUNDLE]). draft-ietf-mpls-crldp-unnum-06.txt [Page 2] Internet Draft draft-ietf-mpls-crldp-unnum-06.txt May 2002 5. 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 ERO 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). 5.1. LSP_TUNNEL_INTERFACE_ID TLV The LSP_TUNNEL_INTERFACE ID TLV has Type to be determined by IETF consensus and length 8. The format is given below. 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. draft-ietf-mpls-crldp-unnum-06.txt [Page 3] Internet Draft draft-ietf-mpls-crldp-unnum-06.txt May 2002 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) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 6. Signalling Unnumbered Links in EROs A new subobject of the Explicit Route Object (ERO) is used to specify unnumbered links. This subobject has the following format: Figure 2: Unnumbered Interface ID Subobject 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 = 0x0805 | Length = 12 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |L| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Router ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface ID (32 bits) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The Type is 0x0805 (Unnumbered Interface ID) 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. 6.1. Processing the IF_ID TLV When an LSR receives a REQUEST message containing the IF_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 matching the tuple 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. 6.2. Processing the ERO object The Unnumbered Interface ID subobject 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 subobject, 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 subobject. With this in mind, the ERO processing in the presence of the Unnumbered Interface ID subobject follows the rules specified in section 4.8.1 of [CR-LDP]. As part of the ERO 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. 7. Security Considerations This document raises no new security concerns for CR-LDP. 8. Acknowledgments Thanks to Rahul Aggarwal for his comments on the text. Thanks too to Bora Akyol and Vach Kompella. draft-ietf-mpls-crldp-unnum-06.txt [Page 5] Internet Draft draft-ietf-mpls-crldp-unnum-06.txt May 2002 9. References 9.1. Normative references [CR-LDP] Jamoussi, B., editor, "Constraint-Based LSP Setup using LDP", RFC3212, December 2001 [GMPLS-SIG] Ashwood, P., et al., "Generalized MPLS - Signalling Functional Description", draft-ietf-generalized-mpls- signalling-08.txt [GMPLS-CRLDP] Ashwood, P., et al., "Generalized MPLS Signaling - CR- LDP Extensions", draft-ietf-mpls-generalized-cr-ldp-06.txt 9.2. Non-normative references [LINK-BUNDLE] Kompella, K., Rekhter, Y., and Berger, L., "Link Bundling in MPLS Traffic Engineering", draft-kompella-mpls- bundle-05.txt (work in progress) [LSP-HIER] Kompella, K., and Rekhter, Y., "LSP Hierarchy with MPLS TE", draft-ietf-mpls-lsp-hierarchy-02.txt (work in progress) [LMP] Lang, J., Mitra, K., et al., "Link Management Protocol (LMP)", draft-ietf-ccamp-lmp-03.txt (work in progress) [GMPLS-ISIS] Kompella, K., Rekhter, Y., Banerjee, A. et al, "IS-IS Extensions in Support of Generalized MPLS", draft-ietf-isis-gmpls- extensions-11.txt (work in progress) [GMPLS-OSPF] Kompella, K., Rekhter, Y., Banerjee, A. et al, "OSPF Extensions in Support of Generalized MPLS", draft-ietf-ccamp-ospf- gmpls-extensions-07.txt (work in progress) draft-ietf-mpls-crldp-unnum-06.txt [Page 6] Internet Draft draft-ietf-mpls-crldp-unnum-06.txt May 2002 10. Author Information Kireeti Kompella Juniper Networks, Inc. 1194 N. Mathilda Ave. Sunnyvale, CA 94089 e-mail: kireeti@juniper.net Yakov Rekhter Juniper Networks, Inc. 1194 N. Mathilda Ave. Sunnyvale, CA 94089 e-mail: yakov@juniper.net Alan Kullberg NetPlane Systems, Inc. Westwood Executive Center 200 Lowder Brook Drive Westwood, MA 02090 e-mail: akullber@netplane.com draft-ietf-mpls-crldp-unnum-06.txt [Page 7]