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Versions: (draft-kompella-mpls-rsvp-unnum) 00 01 02 03 04 05 06 07 RFC 3477

Network Working Group                             Kireeti Kompella
Internet Draft                                    Juniper Networks
Expiration Date: August 2002                         Yakov Rekhter
                                                  Juniper Networks


                 Signalling Unnumbered Links in RSVP-TE

                   draft-ietf-mpls-rsvp-unnum-05.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
   RSVP-TE, one of the MPLS TE signalling protocols, that are needed in
   order to support unnumbered links.













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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 and Record Route
   Objects. This document proposes simple procedures and extensions that
   allow RSVP-TE signalling [GMPLS-RSVP] 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]).





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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 Path message used for
   establishing the LSP that forms the Forwarding Adjacency MUST contain
   the LSP_TUNNEL_INTERFACE_ID object (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 Path message contains the LSP_TUNNEL_INTERFACE_ID object, then
   the tail-end LSR MUST allocate an identifier to that Forwarding
   Adjacency (just like for any other unnumbered link).  Furthermore,
   the Resv message for the LSP MUST contain an LSP_TUNNEL_INTERFACE_ID
   object, 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 IF_ID RSVP_HOP objects,
   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 object. 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 object.


5.1. LSP_TUNNEL_INTERFACE_ID Object

   The LSP_TUNNEL_INTERFACE_ID object has a class number of type
   11bbbbbb (to be assigned by IANA), C-Type of 1 and length of 12. The
   format is given below.


   This object can optionally appear in either a Path message or a Resv
   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.







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   Figure 1: LSP_TUNNEL_INTERFACE_ID Object

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |L|    Type     |     Length    |    Reserved (MUST be zero)    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           Router ID                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Interface ID (32 bits)                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   The Type is 4 (Unnumbered Interface ID). The Length is 12.

   The Interface ID is the identifier assigned to the link by the LSR
   specified by the router ID.


6.1. Processing the IF_ID RSVP_HOP object

   When an LSR receives a Path message containing the IF_ID RSVP_HOP
   object (see [GMPLS-RSVP], [GMPLS-SIG]) 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 using the IF_ID ERROR_SPEC
   object (see [GMPLS-RSVP], [GMPLS-SIG]). The Error code in the object



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   is set to [TBD]. The Error value in the object is set to [TBD].


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 4.3.4.1 of [RSVP-TE].

   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 Path
   message that the node sends to the next hop MUST include the IF_ID
   RSVP_HOP object, with the IP address field of that object set to the
   Router ID of the node, and the Interface ID field of that object set
   to the identifier assigned to the link by the node.


7. Record Route Object

   A new subobject of the Record Route Object (RRO) is used to record
   that the LSP path traversed an unnumbered link. This subobject has
   the following format:

       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     |     Length    |     Flags     | Reserved (MBZ)|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Router ID                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     Interface ID (32 bits)                    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Type is 4 (Unnumbered Interface ID); the Length is 12. Flags are
   defined below.

      0x01  Local protection available

            Indicates that the link downstream of this node is protected
            via a local repair mechanism.  This flag can only be set if
            the Local protection flag was set in the SESSION_ATTRIBUITE



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            object of the cooresponding Path message.

      0x02  Local protection in use

            Indicates that a local repair mechanism is in use to
            maintain this tunnel (usually in the face a an outage of the
            link it was previously routed over).


7.1. Handling RRO

   If at an intermediate node (or at the head-end), the ERO subobject
   that was used to determine the next hop is of type Unnumbered
   Interface ID, and a RRO object was received in the Path message (or
   is desired in the original Path message), an RRO subobject of type
   Unnumbered Interface ID MUST be appended to the received RRO when
   sending a Path message downstream.

   If the ERO subobject that was used to determine the next hop is of
   any other type, the handling procedures of [RSVP-TE] apply. Also, if
   Label Recording is desired, the procedures of [RSVP-TE] apply.


8. Security Considerations

   This document raises no new security concerns for RSVP.


9. IANA Considerations

   The responsible Internet authority (presently called the IANA)
   assigns values to RSVP protocol parameters. The current document
   defines a new subobject for the EXPLICIT_ROUTE object and for the
   ROUTE_RECORD object. The rules for the assignment of subobject
   numbers have been defined in [RSVP-TE], using the terminology of BCP
   26 "Guidelines for Writing an IANA Considerations Section in RFCs".
   Those rules apply to the assignment of subobject numbers for the new
   subobject of the EXPLICIT_ROUTE and ROUTE_RECORD objects.

   Furthermore, the same Internet authority needs to assign a class
   number to the LSP_TUNNEL_INTERFACE_ID object. This must be of the
   form 11bbbbbb (i.e., this is an 8-bit number whose two most
   significant bits are 1).








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10. Acknowledgments

   Thanks to Lou Berger and Markus Jork for pointing out that the RRO
   should be extended in like fashion to the ERO. Thanks also to Rahul
   Aggarwal and Alan Kullberg for their comments on the text. Finally,
   thanks to Bora Akyol and Vach Kompella.


11. 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)

   [RSVP-TE] Awduche, D., Berger, L., Gan, D. H., Li, T., Srinivasan,
   V., and Swallow, G., "RSVP-TE: Extensions to RSVP for LSP Tunnels",
   draft-ietf-mpls-rsvp-lsp-tunnel-08.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-02.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-00.txt (work in progress)

   [GMPLS-RSVP] Ashwood, P., et al., "Generalized MPLS Signalling RSVP-
   TE Extensions", draft-ietf-mpls-generalized-rsvp-te-04.txt (work in
   progress)

   [GMPLS-SIG] Ashwood, P., et al, "Generalized MPLS - Signaling
   Functional Description", draft-ietf-mpls-generalized-signaling-07.txt
   (work in progress)















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12. 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





































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