CCAMP Working Group                              Dimitri Papadimitriou
Internet Draft                                               (Alcatel)
Category: Standard

Expiration Date: August 2006                                March 2006



         Link State Routing Protocols Extensions for ASON Routing

             draft-dimitri-ccamp-gmpls-ason-routing-sol-01.txt



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Copyright Notice

   Copyright (C) The Internet Society (2006). All Rights Reserved.


Abstract

   The Generalized MPLS (GMPLS) suite of protocols has been defined to
   control different switching technologies as well as different
   applications. These include support for requesting TDM connections
   including SONET/SDH and Optical Transport Networks (OTNs).

   This document provides the extensions of the IETF Link State Routing
   Protocols to meet the routing requirements for an Automatically
   Switched Optical Network (ASON) as defined by ITU-T.



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1. 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 [RFC2119].

   The reader is assumed to be familiar with the terminology and
   requirements developed in [ASON-RR] and the evaluation outcomes
   detailed in [ASON-EVAL].

2. Introduction

   There are certain capabilities that are needed to support the ITU-T
   Automatically Switched Optical Network (ASON) control plane
   architecture as defined in [G.8080]. [ASON-RR] details the routing
   requirements for the GMPLS suite of routing protocols to support the
   capabilities and functionality of ASON control planes identified in
   [G.7715] and in [G.7715.1].

   [ASON-EVAL] evaluates the IETF Link State Routing Protocols against
   the requirements identified in [ASON-RR]. Candidate routing protocols
   are IGP (OSPFv2 and IS-IS).

   ASON (Routing) terminology sections are provided in Appendix 1 and 2.

3. Reachability

3.1 OSPFv2

   In order to advertise blocks of reachable address prefixes a
   summarization mechanism is introduced that complements the
   techniques described in [OSPF-NODE].

   This extension takes the form of a network mask (a 32-bit number
   indicating the range of IP addresses residing on a single IP
   network/subnet). The set of local addresses are carried in an OSPF
   TE LSA node attribute TLV (a specific sub-TLV is defined per address
   family, e.g., IPv4 and IPv6).

   The proposed solution is to advertise the local address prefixes of
   a router as new sub-TLVs of the (OSPFv2 TE LSA) Node Attribute top
   level TLV (of Type TBD). This document defines the following sub-
   TLVs:

        - Node IPv4 Local Prefix sub-TLV: Type 3 - Length: variable
        - Node IPv6 Local Prefix sub-TLV: Type 4 - Length: variable

3.1.1 Node IPv4 local prefix sub-TLV

   The node IPv4 local prefix sub-TLV has a type of 3 and contains one
   or more local IPv4 prefixes. It has the following format:



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     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |              3                |             Length            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                         Network Mask 1                        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                         IPv4 Address 1                        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    .                               .                               .
    .                               .                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                         Network Mask n                        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                         IPv4 Address n                        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The length is set to 8 * n where n is the number of local prefixes
   included in the sub-TLV.

   Network mask: A 32-bit number indicating the IPv4 address mask
   for the advertised destination prefix.

   Each <Network mask, IPv4 Address> pair listed as part of this sub-
   TLV represents a reachable destination prefix hosted by the
   advertising Router ID.

   The local addresses that can be learned from TE LSAs i.e. router
   address and TE interface addresses SHOULD not be advertised in the
   node IPv4 local prefix sub-TLV.

3.1.2 Node IPv6 local prefix sub-TLV

   The node IPv6 local prefix sub-TLV has a type of 4 and contains one
   or more local IPv6 prefixes. IPv6 Prefix Representation uses RFC
   2740 Section A.4.1. It 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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |              4                |             Length            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | PrefixLength  | PrefixOptions |             (0)               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    |                     IPv6 Address Prefix 1                     |
    |                                                               |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    .                               .                               .
    .                               .                               .


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    .                               .                               .
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | PrefixLength  | PrefixOptions |             (0)               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    |                     IPv6 Address Prefix n                     |
    |                                                               |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   PrefixLength: length in bits of the prefix.

   PrefixOptions: 8-bit field describing various capabilities
   associated with the prefix (see [RFC2740] Section A.4.2).

   Address Prefix: encoding of the prefix itself as an even multiple of
   32-bit words, padding with zero bits as necessary.

   The Length is set to Sum[n][4 + #32-bit words/4] where n is the
   number of local prefixes included in the sub-TLV.

   The local addresses that can be learned from TE LSAs i.e. router
   address and TE interface addresses SHOULD not be advertised in the
   node IPv6 local prefix sub-TLV.

3.2 IS-IS

   A similar mechanism does not exist for IS-IS as the Extended IP
   Reachability TLV [RFC3784] focuses on IP reachable end-points
   (terminating points), as its name indicates.

   For this purpose, a new Extended TE Reachability TLV (Type TBD) is
   defined as follows

   7 octets of system Id and pseudonode number
   1 octet of length of sub-TLVs
   0-246 octets of sub-TLVs,
      where each sub-TLV consists of a sequence of
         1 octet of sub-type
         1 octet of length of the value field of the sub-TLV
         0-244 octets of value

   Each sub-TLV (Type TBD) is either an IPv4 TE Reachability sub-TLV or
   an IPv6 TE Reachability sub-TLV.

3.2.1 IPv4 TE Reachability sub-TLV

   The "IPv4 TE Reachability" sub-TLV describes TE reachability through
   the specification of a routing prefix, a bit to indicate if the
   prefix is being advertised down from a higher level, and optionally
   the existence of sub-TLVs to allow for later extension. The
   following illustrates encoding of the Value field of this sub-TLV


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       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|    Reserved     | Prefix Len|            Prefix             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            Prefix             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The 6 bits of prefix length can have the values 0-32 and indicate
   the number of significant bits in the prefix. The prefix is encoded
   in the minimal number of octets for the given number of significant
   bits. The remaining bits of prefix are transmitted as zero and
   ignored upon receipt.

   The U bit is described in Section 6.2.

3.2.2 IPv6 TE Reachability sub-TLV

   The "IPv6 TE Reachability" sub-TLV describes TE reachability through
   the specification of a routing prefix, a bit to indicate if the
   prefix is being advertised down from a higher level, and optionally
   the existence of sub-TLVs to allow for later extension. The
   following illustrates encoding of the Value field of this sub-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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |U|   Reserved  |  Prefix Len   |            Prefix             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      ~                             Prefix                            ~
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Prefix  ...   |
      +-+-+-+-+-+-+-+-+

   The 8 bits of prefix length can have the values 0-128 and indicate
   the number of significant bits in the prefix. Only the required
   number of octets of prefix are present. This number can be computed
   from the prefix length octet as follows:

      prefix octets = integer of ((prefix length + 7) / 8)

   The U bit is described in Section 6.2.

4. Link Attribute

4.1 Local Adaptation

   The Local Adaptation is defined as TE link attribute (i.e. sub-TLV)
   that describes the cross/inter-layer relationships.


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   The Interface Switching Capability Descriptor (ISCD) TE Attribute
   [RFC4202] identifies the ability of the TE link to support cross-
   connection to another link within the same layer and the ability to
   use a locally terminated connection that belongs to one layer as a
   data link for another layer (adaptation capability). However, the
   information associated to the ability to terminate connections
   within that layer (referred to as the termination capability) is
   embedded with the adaptation capability.

   For instance, a link between two optical cross-connects will contain
   at least one ISCD attribute describing LSC switching capability.
   Whereas a link between an optical cross-connect and an IP/MPLS LSR
   will contain at least two ISCD attributes: one for the description
   of the LSC termination capability and one for the PSC adaptation
   capability.

   Note that per [RFC4202], an interface may have more than one ISCD
   sub-TLV. Hence, the corresponding advertisements should not result
   in any compatibility issue.

4.1.2 OSPFv2

   In OSPFv2, the Interface Switching Capability Descriptor is a sub-
   TLV (of type TBA) of the Link TLV (of type 2) [RFC4203].

   The adaptation and termination capabilities are advertised using two
   separate ISCD sub-TLVs within the same top-level link TLV.

4.1.2 IS-IS

   In IS-IS, the Interface Adaptation Capability Descriptor is a sub-
   TLV (of type TBA) of the Extended IS Reachability TLV (of type 22)
   [RFC4205].

   The adaptation and termination capabilities are advertised using two
   separate ISCD sub-TLVs within the same Extended IS Reachability TLV.

4.2 Technology Specific Bandwidth Accounting

   GMPLS Routing defines an Interface Switching Capability Descriptor
   (ISCD) that delivers among others the information about the
   (maximum/minimum) bandwidth per priority an LSP can make use of.

   In the ASON context, accounting on per timeslot basis using 32-bit
   tuples of the form <signal_type (8 bits); number of unallocated
   timeslots (24 bits)> may optionally be incorporated in the
   technology specific field of the ISCD TE link attribute when the
   switching capability field is set to TDM value. When included,
   format and encoding MUST follow the rules defined in [RFC4202].




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   The purpose is purely informative: there is no mandatory processing
   or topology/traffic-engineering significance associated to this
   information.

4.2.1 OSPFv2

   In OSPF, the Interface Switching Capability Descriptor is a sub-TLV
   (of type 15) of the Link TLV (of type 2).

4.2.2 IS-IS

   In IS-IS, the Interface Switching Capability Descriptor is a sub-TLV
   (of type 21) of the Extended IS Reachability TLV (of type 22).

5. Routing Information Scope

   The Ri is a logical control plane entity that is associated to a
   control plane "router". The latter is the source for topology
   information that it generates and shares with other control plane
   "routers". The Ri is identified by the (advertising) Router_ID. The
   routing protocol MUST support a single Ri advertising on behalf of
   more than one Li. Each Li is identified by a unique TE Router ID.

5.1 Link Advertisement (Local and Remote TE Router ID sub-TLV)

   A Router_ID (Ri) advertising on behalf multiple TE Router_ID (Li's)
   creates a 1:N relationship between the Router_ID and the TE
   Router_ID. As the link local and link remote (unnumbered) ID
   association is not unique per node (per Li unicity), the
   advertisement needs to indicate the remote Lj value and rely on the
   initial discovery process to retrieve the [Li;Lj] relationship. In
   brief, as unnumbered links have their ID defined on per Li bases,
   the remote Lj needs to be identified to scope the link remote ID to
   the local Li. Therefore, the routing protocol MUST be able to
   disambiguate the advertised TE links so that they can be associated
   with the correct TE Router ID.

5.1.1 OSPFv2

   For this purpose, a new sub-TLV of the (OSPFv2 TE LSA) top level
   Link TLV is introduced that defines the local and the remote
   TE_Router_ID.

   The type of this sub-TLV is 17, and length is eight octets. The
   value field of this sub-TLV contains four octets of Local TE Router
   Identifier followed by four octets of Remote TE Router Identifier.
   The value of the Remote TE Router Identifier SHOULD NOT be set to 0.

   The format of this sub-TLV is the following:

     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


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    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |              17               |             Length            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                 Local TE Router Identifier                    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                Remote TE Router Identifier                    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   This sub-TLV is optional and SHOULD only be included as part of the
   top level Link TLV if the Router_ID is advertising on behalf of more
   than one TE_Router_ID. In any other case, this sub-TLV SHOULD be
   omitted.

   Note: The Link ID sub-TLV that identifies the other end of the link
   (i.e. Router ID of the neighbor for point-to-point links) MUST
   appear exactly once per Link TLV.

5.1.2 IS-IS

   For this purpose, a new sub-TLV of the Extended IS Reachability TLV
   (Type 22, RFC 3784) is introduced that defines the local and the
   remote TE_Router_ID.

   The type of this sub-TLV is TBD, and length is eight octets. The
   value field of this sub-TLV contains four octets of Local TE Router
   Identifier followed by four octets of Remote TE Router Identifier.
   The value of the Remote TE Router Identifier SHOULD NOT be set to 0.

   The format of the value field of this sub-TLV is the following:

     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                 Local TE Router Identifier                    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                Remote TE Router Identifier                    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   This sub-TLV is optional and SHOULD only be included as part of the
   Extended IS Reachability TLV if the RC is advertising on behalf of
   more than one TE_Router_ID. In any other case, this sub-TLV SHOULD
   be omitted.

5.2 Reachability Advertisement (Local TE Router ID sub-TLV)

   When the Router_ID advertises on behalf of multiple TE Router_IDs,
   the routing protocol MUST be able to associate the advertised
   reachability information with the correct TE Router ID.

5.2.1 OSPFv2




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   For this purpose, a new sub-TLV of the (OSPFv2 TE LSA) top level
   Node Attribute TLV is introduced. This TLV associates the local
   prefixes (sub-TLV 3 and 4, see above) to a given TE Router_ID.

   The type of this sub-TLV is 5, and length is four octets. The value
   field of this sub-TLV contains four octets of Local TE Router
   Identifier [RFC3630].

   The format of this sub-TLV is the following:

     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |              5                |             Length            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                 Local TE Router Identifier                    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   This sub-TLV is optional and SHOULD only be included as part of the
   Node Attribute TLV if the Router_ID is advertising on behalf of more
   than one TE_Router_ID. In any other case, this sub-TLV SHOULD be
   omitted.

5.2.2 IS-IS

   For this purpose, a new sub-TLV of the newly defined Extended TE
   Reachability TLV is introduced that defines the local TE_Router_ID.

   The type of this sub-TLV is TBD, and length is four octets. The
   value field of this sub-TLV contains four octets of Local TE Router
   Identifier [RFC3784].

   The format of the value field of this sub-TLV is the following:

     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                 Local TE Router Identifier                    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   This sub-TLV is optional and SHOULD only be included as part of the
   Extended TE Reachability TLV if the RC is advertising on behalf of
   more than one TE_Router_ID. In any other case, this sub-TLV SHOULD
   be omitted.

6. Routing Information Dissemination

6.1 OSPFv2

   RC disseminates downward/upward the hierarchy by re-originating this
   routing information as Opaque TE LSA (Opaque Type 1) of LS Type 10.



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   The information that MAY be exchanged between adjacent levels
   includes the Router_Address, Link and Node_Attribute top level TLV.

   The Opaque TE LSA re-origination is governed as follows:
   - If the target interface is associated to the same area than the
     one associated with the receiving interface, the Opaque LSA MUST
     NOT be re-originated out that interface.
   - If a match is found between the Advertising Router ID in the
     received Opaque TE LSA and one of the Router ID belonging to the
     area of the target interface, the Opaque LSA MUST NOT be re-
     originated out that interface.
   - If these two conditions are met the Opaque TE LSA MAY be re-
     originated.

   The re-originated content MAY be transformed e.g. filtered, as long
   as the resulting routing information is consistent. In particular,
   when than one RC are bound to adjacent levels and both allowed to
   redistribute routing information it is expected that these
   transformation are performed in consistent manner. Definition of
   these policy mechanisms is outside the scope of this document.

   In practice, and in order to avoid scalability and processing
   overhead, routing information re-distributed downward/upward the
   hierarchy is expected to include reachability information (see
   Section 3.1) and upon strict policy control link topology
   information.

6.1.1 Discovery and Selection

   In order to discover RCs that are capable to disseminate routing
   information upward the routing hierarchy, the following Capability
   Descriptor bit [OSPF-TE-CAP] are defined:

   - U bit: when set, this flag indicates that the RC is capable to
     disseminate routing information upward the adjacent level.

   In case of multiple supporting RCs, the RC with the highest Router
   ID SHOULD be selected. More precisely, the RC with the highest
   Router ID among the RCs having set the U bit SHOULD be selected as
   the RC for upward dissemination of routing information. It is
   expected that other RCs will not participate in the upward
   dissemination of routing information as long as the opaque LSA
   information corresponding to the highest Router ID RC does not reach
   MaxAge.

   Note that alternatively if this information cannot be discovered
   automatically, it MUST be manually configured.

   The same mechanism is used for selecting the RC taking in charge
   dissemination of routing information downward the hierarchy with the
   restriction that the RC selection process needs to take into account
   that an upper level may be adjacent to one or more lower levels. For


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   this purpose a specific TLV indexing the (lower) area ID to which
   the RC's are capable to disseminate routing information is needed.

   OSPF Associated Area ID TLV format carried in the OSPF router
   information LSA [OSPF-CAP] is defined. This TLV 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            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Associated Area ID                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type (16 bits): identifies the TLV type
   Length (16 bits): length of the value field in octets
   Value (32 bits): Associated Area ID whose value space is the Area ID
   as defined in [RFC2328].

   Note that this information MUST be present when the D bit is set. To
   discover RCs that are capable to disseminate routing information
   downward the routing hierarchy, the following Capability Descriptor
   bit [OSPF-TE-CAP] is defined, that MUST be advertised together with
   the OSPF Area ID TLV:

   - D bit: when set, this flag indicates that the RC is capable to
     disseminate routing information downward the adjacent level.

   In case of multiple supporting RCs for the same Associated Area ID,
   the RC with the highest Router ID SHOULD be selected. More
   precisely, the RC with the highest Router ID among the RCs having
   set the D bit SHOULD be selected as the RC for downward
   dissemination of routing information. It is expected that other RCs
   for the same Associated Area ID will not participate in the downward
   dissemination of routing information as long as the opaque LSA
   information corresponding to the highest Router ID RC does not reach
   MaxAge.

   Note that alternatively if this information cannot be discovered
   automatically, it MUST be manually configured.

   The OSPF Router information opaque LSA (opaque type of 4, opaque ID
   of 0) and its content in particular, the Router Informational
   Capabilities TLV [OSPF-CAP] and TE Node Capability Descriptor TLV
   [OSPF-TE-CAP] MUST NOT be re-originated.

6.1.2 Loop prevention

   When more than one RC are bound to adjacent levels of the hierarchy,
   configured and selected to redistribute upward and downward the
   routing information, a specific mechanism is required to avoid


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   looping/re-introduction of routing information back to the upper
   level. In all other cases, the procedure described in this section
   is optional.

   When these conditions are met, it is necessary to have a mean by
   which an RC receiving an Opaque TE LSA re-originated downward by an
   RC associated to the same area omits to re-originate back the
   content of this LSA upward into the (same) upper level.

   Thus we need some way of filtering the downward/onward re-originated
   Opaque TE LSA.

   For opaque LSAs including the Router Address TLV, if the Router
   address has been already installed into the TEDB, the LSA should not
   be re-originated since this address belongs to a router part of the
   target area.

   For opaque LSAs including the Link TLV, if the Link ID has been
   already installed into the TEDB, the LSA should not be re-originated
   since the corresponding router ID belongs to a router part of the
   target area.

   For opaque LSAs including the Node Attribute TLV, if one of the
   included prefixes has been already installed into the TEDB, the LSA
   should not be re-originated with that prefix since the corresponding
   reachable end-points belonging to a router part of the target area.
   If no prefix remains, the LSA SHOULD not be re-originated.

6.2. IS-IS

6.2.1 Discovery and Selection

   In order to discover RCs that are capable to disseminate routing
   information upward the routing hierarchy, the following Capability
   Descriptor bit [ISIS-TE-CAP] are defined:

   - U bit: when set, this flag indicates that the RC is capable to
     disseminate routing information upward the adjacent level.

   In case of multiple supporting RCs, the RC with the highest Router
   ID [ISIS-CAP] SHOULD be selected. More precisely, the RC with the
   highest Router ID among the RCs having set the U bit SHOULD be
   selected as the RC for upward dissemination of routing information.
   It is expected that other RCs will not participate in the upward
   dissemination of routing information as long as the routing
   information corresponding to the highest Router ID RC is not
   withdrawn.

   Note that alternatively if this information cannot be discovered
   automatically, it MUST be manually configured.




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   The same mechanism is used for selecting the RC taking in charge
   dissemination of routing information downward the hierarchy with the
   restriction that the RC selection process needs to take into account
   that an upper level may be adjacent to one or more lower levels. For
   this purpose a specific TLV indexing the (lower) ISIS area ID to
   which the RC's are capable to disseminate routing information is
   needed.

   To discover RCs that are capable to disseminate routing information
   downward the routing hierarchy, the following Capability Descriptor
   bit [ISIS-TE-CAP] is defined:

   - D bit: when set, this flag indicates that the RC is capable to
     disseminate routing information downward the adjacent level.

   In case of multiple supporting RCs for the same ISIS Area ID, the RC
   with the highest Router ID SHOULD be selected. More precisely, the
   RC with the highest Router ID among the RCs having set the D bit
   SHOULD be selected as the RC for downward dissemination of routing
   information. It is expected that other RCs for the same Area ID will
   not participate in the downward dissemination of routing information
   as long as the routing information corresponding to the highest
   Router ID RC is not withdrawn.

   Note that alternatively if this information cannot be discovered
   automatically, it MUST be manually configured.

   The ISIS Router Capability TLV [ISIS-CAP] and its content in
   particular MUST NOT be redistributed between adjacent levels.

6.2.2 Loop prevention

   As described in [RFC3784], to prevent this looping of TE reachable
   prefixes between levels, an up/down bit (U bit) is defined in the
   newly defined extended TE reachability TLV.

   The up/down bit MUST be set to 0 when a prefix is first injected
   into IS-IS.  If a prefix is advertised from a higher level to a
   lower level (e.g. level 2 to level 1), the bit MUST be set to 1,
   indicating that the prefix has traveled down the hierarchy. Prefixes
   that have the up/down bit set to 1 may only be advertised down the
   hierarchy, i.e. to lower levels.

   For the extended IS reachability TLV, the same re-origination rules
   as described in Section 6.1.2 applies.

7. OSPFv2 Extensions

7.1 Compatibility

   Extensions specified in this document are associated to the



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   OSPFv2 TE LSA:

   o) Router Address top level TLV (Type 1):
      - no additional sub-TLV

   o) Link top level TLV (Type 2):
      - Local and Remote TE Router ID sub-TLV: optional sub-TLV for
        scoping link attributes per TE_Router ID

   o) Node Attribute top level TLV (Type TBD):
      - Node IPv4 Local Prefix sub-TLVs: optional sub-TLV for IPv4
        reachability advertisement
      - Node IPv6 Local Prefix sub-TLVs: optional sub-TLV for IPv6
        reachability advertisement
      - Local TE Router ID sub-TLV: optional sub-TLV for scoping
        reachability per TE_Router ID

   OSPFv2 RI LSA:

   o) Routing information dissemination
      - U and D bit in Capability Descriptor TLV [OSPF-TE-CAP]
      - Associated Area ID TLV in the OSPF Routing Information LSA
        [OSPF-CAP]

7.2 Scalability

   o) Routing information exchange upward/downward the hierarchy
   between adjacent areas SHOULD by default be limited to reachability.
   In addition, several transformation such as prefix aggregation are
   recommended when allowing decreasing the amount of information re-
   originated by a given RC without impacting consistency.

   o) Routing information exchange upward/downward the hierarchy when
   involving TE attributes MUST be under strict policy control. Pacing
   and min/max thresholds for triggered updates are strongly
   recommended.

8. IS-IS Extensions and Compatibility

   TBD

9. Acknowledgements

   The authors would like to thank Alan Davey and Adrian Farrel for
   their useful comments and suggestions.

10. References

11.1 Normative References





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   [OSPF-NODE]  R.Aggarwal, and K.Kompella, "Advertising a Router's
                Local Addresses in OSPF TE Extensions," Internet Draft,
                (work in progress), draft-ietf-ospf-te-node-addr-
                02.txt, March 2005.

   [RFC2026]    S.Bradner, "The Internet Standards Process --
                Revision 3", BCP 9, RFC 2026, October 1996.

   [RFC2328]    J.Moy, "OSPF Version 2", RFC 2328, April 1998.

   [RFC2740]    R.Coltun et al. "OSPF for IPv6", RFC 2740, December
                1999.

   [RFC2119]    S.Bradner, "Key words for use in RFCs to Indicate
                Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3477]    K.Kompella et al. "Signalling Unnumbered Links in
                Resource ReSerVation Protocol - Traffic Engineering
                (RSVP-TE)", RFC 3477, January 2003.

   [RFC3630]    D.Katz et al. "Traffic Engineering (TE) Extensions to
                OSPF Version 2", RFC 3630, September 2003.

   [RFC3667]    S.Bradner, "IETF Rights in Contributions", BCP 78,
                RFC 3667, February 2004.

   [RFC3668]    S.Bradner, Ed., "Intellectual Property Rights in IETF
                Technology", BCP 79, RFC 3668, February 2004.

   [RFC3784]    H.Smit and T.Li, "Intermediate System to Intermediate
                System (IS-IS) Extensions for Traffic Engineering (TE),"
                RFC 3784, June 2004.

   [RFC3946]    E.Mannie, and D.Papadimitriou, (Editors) et al.,
                "Generalized Multi-Protocol Label Switching Extensions
                for SONET and SDH Control," RFC 3946, October 2004.

   [RFC4202]    Kompella, K. (Editor) et al., "Routing Extensions in
                Support of Generalized MPLS," RFC 4202, October 2005.

8.2 Informative References

   [ASON-EVAL]  C.Hopps et al. "Evaluation of existing Routing Protocols
                against ASON Routing Requirements", Work in progress,
                draft-ietf-ccamp-gmpls-ason-routing-eval-02.txt, October
                2005.

   [ASON-RR]    D.Brungard et al. "Requirements for Generalized MPLS
                (GMPLS) Routing for Automatically Switched Optical
                Network (ASON)," RFC 4258, November 2005.

   For information on the availability of ITU Documents, please see


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   http://www.itu.int

   [G.7715]     ITU-T Rec. G.7715/Y.1306, "Architecture and
                Requirements for the Automatically Switched Optical
                Network (ASON)," June 2002.

   [G.7715.1]   ITU-T Draft Rec. G.7715.1/Y.1706.1, "ASON Routing
                Architecture and Requirements for Link State Protocols,"
                November 2003.

   [G.8080]     ITU-T Rec. G.8080/Y.1304, "Architecture for the
                Automatically Switched Optical Network (ASON),"
                November 2001 (and Revision, January 2003).

9. Author's Addresses

   Dimitri Papadimitriou (Alcatel)
   Francis Wellensplein 1,
   B-2018 Antwerpen, Belgium
   Phone: +32 3 2408491
   EMail: dimitri.papadimitriou@alcatel.be

































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Appendix 1: ASON Terminology

   This document makes use of the following terms:

   Administrative domain: (see Recommendation G.805) for the purposes of
   [G7715.1] an administrative domain represents the extent of resources
   which belong to a single player such as a network operator, a service
   provider, or an end-user. Administrative domains of different players
   do not overlap amongst themselves.

   Control plane: performs the call control and connection control
   functions. Through signaling, the control plane sets up and releases
   connections, and may restore a connection in case of a failure.

   (Control) Domain: represents a collection of (control) entities that
   are grouped for a particular purpose. The control plane is subdivided
   into domains matching administrative domains. Within an
   administrative domain, further subdivisions of the control plane are
   recursively applied. A routing control domain is an abstract entity
   that hides the details of the RC distribution.

   External NNI (E-NNI): interfaces are located between protocol
   controllers between control domains.

   Internal NNI (I-NNI): interfaces are located between protocol
   controllers within control domains.

   Link: (see Recommendation G.805) a "topological component" which
   describes a fixed relationship between a "subnetwork" or "access
   group" and another "subnetwork" or "access group". Links are not
   limited to being provided by a single server trail.

   Management plane: performs management functions for the Transport
   Plane, the control plane and the system as a whole. It also provides
   coordination between all the planes. The following management
   functional areas are performed in the management plane: performance,
   fault, configuration, accounting and security management

   Management domain: (see Recommendation G.805) a management domain
   defines a collection of managed objects which are grouped to meet
   organizational requirements according to geography, technology,
   policy or other structure, and for a number of functional areas such
   as configuration, security, (FCAPS), for the purpose of providing
   control in a consistent manner. Management domains can be disjoint,
   contained or overlapping. As such the resources within an
   administrative domain can be distributed into several possible
   overlapping management domains. The same resource can therefore
   belong to several management domains simultaneously, but a management
   domain shall not cross the border of an administrative domain.

   Subnetwork Point (SNP): The SNP is a control plane abstraction that
   represents an actual or potential transport plane resource. SNPs (in


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   different subnetwork partitions) may represent the same transport
   resource. A one-to-one correspondence should not be assumed.

   Subnetwork Point Pool (SNPP): A set of SNPs that are grouped together
   for the purposes of routing.

   Termination Connection Point (TCP): A TCP represents the output of a
   Trail Termination function or the input to a Trail Termination Sink
   function.

   Transport plane: provides bi-directional or unidirectional transfer
   of user information, from one location to another. It can also
   provide transfer of some control and network management information.
   The Transport Plane is layered; it is equivalent to the Transport
   Network defined in G.805 Recommendation.

   User Network Interface (UNI): interfaces are located between protocol
   controllers between a user and a control domain. Note: there is no
   routing function associated with a UNI reference point.



































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Appendix 2: ASON Routing Terminology

   This document makes use of the following terms:

   Routing Area (RA): a RA represents a partition of the data plane and
   its identifier is used within the control plane as the representation
   of this partition. Per [G.8080] a RA is defined by a set of sub-
   networks, the links that interconnect them, and the interfaces
   representing the ends of the links exiting that RA. A RA may contain
   smaller RAs inter-connected by links. The limit of subdivision
   results in a RA that contains two sub-networks interconnected by a
   single link.

   Routing Database (RDB): repository for the local topology, network
   topology, reachability, and other routing information that is updated
   as part of the routing information exchange and may additionally
   contain information that is configured. The RDB may contain routing
   information for more than one Routing Area (RA).

   Routing Components: ASON routing architecture functions. These
   functions can be classified as protocol independent (Link Resource
   Manager or LRM, Routing Controller or RC) and protocol specific
   (Protocol Controller or PC).

   Routing Controller (RC): handles (abstract) information needed for
   routing and the routing information exchange with peering RCs by
   operating on the RDB. The RC has access to a view of the RDB. The RC
   is protocol independent.

   Note: Since the RDB may contain routing information pertaining to
   multiple RAs (and possibly to multiple layer networks), the RCs
   accessing the RDB may share the routing information.

   Link Resource Manager (LRM): supplies all the relevant component and
   TE link information to the RC. It informs the RC about any state
   changes of the link resources it controls.

   Protocol Controller (PC): handles protocol specific message exchanges
   according to the reference point over which the information is
   exchanged (e.g. E-NNI, I-NNI), and internal exchanges with the RC.
   The PC function is protocol dependent.













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