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Versions: (draft-dimitri-ccamp-gmpls-ason-routing-ospf) 00 01 02 03 04 05 06 07 08 09 RFC 5787

Network Working Group                              Dimitri Papadimitriou
Internet Draft                                          (Alcatel-Lucent)
Category: Experimental
Created: October 29, 2008
Expires: April 29, 2008


           OSPFv2 Routing Protocols Extensions for ASON Routing

              draft-ietf-ccamp-gmpls-ason-routing-ospf-06.txt


Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
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Abstract

   The ITU-T has defined an architecture and requirements for operating
   an Automatically Switched Optical Network (ASON).

   The Generalized Multiprotocol Label Switching (GMPLS) protocol suite
   is designed to provide a control plane for a range of network
   technologies including optical networks such as time division
   multiplexing (TDM) networks including SONET/SDH and Optical Transport
   Networks (OTNs), and lambda switching optical networks.

   The requirements for GMPLS routing to satisfy the requirements of
   ASON routing, and an evaluation of existing GMPLS routing protocols
   are provided in other documents. This document defines to the OSPFv2
   Link State Routing Protocol to meet the routing requirements for
   routing in an ASON.

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   Note that this work is scoped to the requirements and evaluation
   expressed in RFC 4258 and RFC 4652 and the ITU-T Recommendations
   current when those documents were written. Future extensions of
   revisions of this work may be necessary if the ITU-T Recommendations
   are revised or if new requirements are introduced into a revision of
   RFC 4258.


Table of Contents

     1. Introduction................................................. 3
     1.1. Conventions Used In This Document.......................... 4
     2. Routing Areas, OSPF Areas, and Protocol Instances............ 4
     3. Reachability................................................. 4
     3.1 Node IPv4 Local Prefix Sub-TLV.............................. 5
     3.2 Node IPv6 Local Prefix Sub-TLV.............................. 6
     4. Link Attribute............................................... 7
     4.1 Local Adaptation............................................ 7
     4.2 Bandwidth Accounting........................................ 8
     5. Routing Information Scope.................................... 8
     5.1 Terminology and Identification.............................. 8
     5.2 Link Advertisement (Local and Remote TE Router ID Sub-TLV).. 9
     5.3 Reachability Advertisement (Local TE Router ID Sub-TLV).... 10
     6. Routing Information Dissemination........................... 10
     6.1 Import/Export Rules........................................ 11
     6.2 Discovery and Selection.................................... 12
     6.2.1 Upward Discovery and Selection........................... 12
     6.2.2 Downward Discovery and Selection......................... 12
     6.3 Loop Prevention............................................ 14
     6.3.1 Associated RA ID......................................... 15
     6.3.2 Processing............................................... 15
     6.4 Resiliency................................................. 16
     6.5 Neighbor Relationship and Routing Adjacency................ 17
     6.6 Reconfiguration............................................ 17
     7. OSPFv2 Extensions........................................... 18
     7.1 Compatibility.............................................. 18
     7.2 Scalability................................................ 19
     8. Security Considerations..................................... 19
     9. IANA Considerations......................................... 20
     9.1 Sub-TLVs for the OSPF Opaque TE LSA........................ 20
     9.2 OSPF RI LSA................................................ 20
     9.2.1 RI Capability Bits....................................... 20
     9.2.2 RI LSA TLVs.............................................. 21
     10. References................................................. 21
     10.1 Normative References...................................... 21
     10.2 Informative References.................................... 22
     11. Author's Address........................................... 23
     Appendix 1: ASON Terminology................................... 24
     Appendix 2: ASON Routing Terminology........................... 26


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1. Introduction

   The Generalized Multiprotocol Label Switching (GMPLS) [RFC3945]
   protocol suite is designed to provide a control plane for a range of
   network technologies including optical networks such as time division
   multiplexing (TDM) networks including SONET/SDH and Optical Transport
   Networks (OTNs), and lambda switching optical networks.

   The ITU-T defines the architecture of the Automatically Switched
   Optical Network (ASON) in [G.8080].

   [RFC4258] 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].

   [RFC4652] evaluates the IETF Link State Routing Protocols against the
   requirements identified in [RFC4258]. Section 7.1 of [RFC4652]
   summarizes the capabilities to be provided by OSPFv2 [RFC2328] in
   support of ASON routing. This document details the OSPFv2 specifics
   for ASON routing.

   Multi-layer transport networks are constructed from multiple networks
   of different technologies operating in a client-server relationship.
   The ASON routing model includes the definition of routing levels that
   provide scaling and confidentiality benefits. In multi-level routing,
   domains called routing areas (RAs) are arranged in a hierarchical
   relationship. Note that as described in [RFC4652] there is no implied
   relationship between multi-layer transport networks and multi-level
   routing. The multi-level routing mechanisms described in this
   document work for both single layer and multi-layer networks.

   Implementations may support a hierarchical routing topology (multi-
   level) for multiple transport network layers and/or a hierarchical
   routing topology for a single transport network layer.

   This document details the processing of the generic (technology-
   independent) link attributes that are defined in [RFC3630],
   [RFC4202], and [RFC4203] and that are extended in this document. As
   detailed in Section 4.2, technology-specific traffic engineering
   attributes (and their processing) may be defined in other documents
   that complement this document.

   Note that this work is scoped to the requirements and evaluation
   expressed in [RFC4258] and [RFC4652] and the ITU-T Recommendations
   current when those documents were written. Future extensions of
   revisions of this work may be necessary if the ITU-T Recommendations
   are revised or if new requirements are introduced into a revision of
   [RFC4258].


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1.1. 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 [RFC4258] and the evaluation outcomes
   detailed in [RFC4652].

   General ASON terminology is provided in Appendix 1. ASON routing
   terminology is described in Appendix 2.

2. Routing Areas, OSPF Areas, and Protocol Instances

   An ASON routing area (RA) represents a partition of the data plane
   and its identifier is used within the control plane as the
   representation of this partition.

   RAs are arranged in hierarchical levels such that any one RA may
   contain multiple other RAs, and is wholly contained by a single RA.
   Thus, an RA may contain smaller RAs inter-connected by links. The
   limit of the subdivision results is an RA that contains just two
   sub-networks interconnected by a single link.

   An ASON RA can be mapped to an OSPF area, but the hierarchy of ASON
   RA levels does not map to the hierarchy of OSPF routing areas.
   Instead, successive hierarchical levels of RAs MUST be represented by
   separate instances of the protocol. Thus, inter-level routing
   information exchange (as described in Section 6) involves the export
   and import of routing information between protocol instances.

   An ASON RA may therefore be identified by the combination of its OSPF
   instance identifier and its OSPF area identifier. With proper and
   careful network-wide configuration, this can be achieved using just
   the OSPF area identifier, and this process is RECOMMENDED in this
   document. These concepts and the subsequent handling of network
   reconfiguration is discussed in Section 6.

3. Reachability

   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 OSPFv2


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   TE LSA node attribute TLV (a specific sub-TLV is defined per address
   family, i.e., IPv4 and IPv6, used as network-unique identifiers).

   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. 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 Node IPv4 Local Prefix Sub-TLV

   The Type of the Node IPv4 Local Prefix sub-TLV is 3. The Value field
   of this sub-TLV contains one or more local IPv4 prefixes. The Length
   is set to 8 x n, where n is the number of local IPv4 prefixes
   included in the sub-TLV.

   The Node IPv4 Local Prefix sub-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 (3)             |         Length (8 x n)        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                         Network Mask 1                        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                         IPv4 Address 1                        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    //                             ...                             //
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                         Network Mask n                        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                         IPv4 Address n                        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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

   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 Opaque TE LSAs. That is,
   router address and TE interface addresses SHOULD NOT be advertised
   in the node IPv4 local prefix sub-TLV.



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3.2 Node IPv6 Local Prefix Sub-TLV

   The Type of the Node IPv6 Local Prefix sub-TLV is 4. The Value field
   of this sub-TLV contains one or more local IPv6 prefixes. IPv6
   Prefix representation uses [RFC5340] Section A.4.1.

   The Node IPv6 Local Prefix sub-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 (4)             |            Length             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | PrefixLength  | PrefixOptions |             (0)               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    |                     IPv6 Address Prefix 1                     |
    |                                                               |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    //                             ...                             //
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | PrefixLength  | PrefixOptions |             (0)               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    |                     IPv6 Address Prefix n                     |
    |                                                               |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     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 encoding of
       each prefix potentially using fewer than four 32-bit words is
       described below.

     PrefixLength: length in bits of the prefix.

     PrefixOptions: 8-bit field describing various capabilities
       associated with the prefix (see [RFC5340] Section A.4.2).

     IPv6 Address Prefix "i": encoding of the prefix "i" itself as an
       even multiple of 32-bit words, padding with zero bits as
       necessary.

   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.

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4. Link Attribute

   [RFC4652] provides a map between link attributes and characteristics
   and their representation in sub-TLVs of the top level Link TLV of the
   Opaque TE LSA [RFC3630] and [RFC4203], with the exception of the
   Local Adaptation (see below). Advertisement of this information
   SHOULD be supported on a per-layer basis, i.e., one Opaque TE LSA per
   switching capability (and per bandwidth granularity, e.g., low-order
   virtual container and high-order virtual container).

4.1 Local Adaptation

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

   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 the 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.

   In OSPFv2, the Interface Switching Capability Descriptor (ISCD) is a
   sub-TLV (of type 15) of the top-level 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.

   Per [RFC4202] and [RFC4203], an interface MAY have more than one
   ISCD sub-TLV. Hence, the corresponding advertisements should not
   result in any compatibility issues.

   Further refinement of the ISCD sub-TLV for multi-layer networks is
   outside the scope of this document.







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4.2 Bandwidth Accounting

   GMPLS Routing defines an Interface Switching Capability Descriptor
   (ISCD) that delivers, among other things, information about the
   (maximum/minimum) bandwidth per priority that an LSP can make use of.
   Per [RFC4202] and [RFC4203], one or more ISCD sub-TLVs can be
   associated with an interface. This information, combined with the
   Unreserved Bandwidth (sub-TLV defined in [RFC3630], Section 2.5.8),
   provides the basis for bandwidth accounting.

   In the ASON context, additional information may be included when the
   representation and information in the other advertised fields are
   not sufficient for a specific technology (e.g., SDH). The definition
   of technology-specific information elements is beyond the scope of
   this document. Some technologies will not require additional
   information beyond what is already defined in [RFC3630], [RFC4202],
   and [RFC4203].

5. Routing Information Scope

5.1. Terminology and Identification

   The definition of short-hand terminology introduced in [RFC4652] is
   repeated here for clarity.

   - Pi is a physical (bearer/data/transport plane) node.

   - Li is a logical control plane entity that is associated to a single
     data plane (abstract) node. Each Li is identified by a unique TE
     Router-ID. The latter is a control plane identifier, defined as the
     Router Address top level TLV of the Type 1 TE LSA [RFC3630].

     Note: the Router Address top-level TLV definition, processing and
     usage remain per [RFC3630]. This TLV specifies a stable IP address
     of the advertising router (Ri) that is always reachable if there is
     any IP connectivity to it (e.g. via the Data Communication
     Network). Moreover, each advertising router advertises a unique,
     reachable IP address for each Pi on behalf of which it makes
     advertisements.

   - 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
     (32-bit) [RFC2328].

     The Router-ID, which is represented by Ri and which corresponds to
     the RC-ID [RFC4258], does not enter into the identification of the


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     logical entities representing the data plane resources such as
     links. The Routing DataBase (RDB) is associated to the Ri.

   Note: Aside from the Li/Pi mappings, these identifiers are not
   assumed to be in a particular entity relationship except that the Ri
   may have multiple Lis in its scope. The relationship between Ri and
   Li is simple at any moment in time: an Li may be advertised by only
   one Ri at any time. However, an Ri may advertise a set of one or
   more Lis. Hence, the OSPFv2 routing protocol must support a single
   Ri advertising on behalf of more than one Li.

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

   A Router-ID (Ri) advertising on behalf multiple TE Router_IDs (Lis)
   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.

   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 the Local and Remote TE Router-ID sub-TLV is 17, and its
   length is 8 octets. The Value field of this sub-TLV contains 4
   octets of Local TE Router Identifier followed by 4 octets of Remote
   TE Router Identifier. The value of the Local and the Remote TE
   Router Identifier SHOULD NOT be set to 0.

   The format of the Local and Remote TE Router-ID sub-TLV 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 (17)            |          Length (8)           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                 Local TE Router Identifier                    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                 Remote TE Router Identifier                   |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   This sub-TLV is only required to be included as part of the top


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   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 except if operator plans to start of with 1 Li and
   progressively add more Li's (under the same Ri) such as to maintain
   consistency.

   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. This sub-TLV MUST be processed as
   defined in [RFC3630].

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

   When the Router-ID is advertised on behalf of multiple TE Router-IDs
   (Lis), the routing protocol MUST be able to associate the advertised
   reachability information with the correct TE Router-ID.

   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 the Local TE Router-ID sub-TLV is 5, and its Length is 4
   octets. The value field of this sub-TLV contains the Local TE Router
   Identifier [RFC3630] encoded over 4 octets.

   The format of the Local TE Router-ID sub-TLV 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 (5)             |          Length (4)           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                 Local TE Router Identifier                    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   This sub-TLV is only required to be included 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.

6. Routing Information Dissemination

   An ASON routing area (RA) represents a partition of the data plane
   and its identifier is used within the control plane as the
   representation of this partition. A RA may contain smaller RAs inter-
   connected by links. The limit of the subdivision results is an RA
   that contains two sub-networks interconnected by a single link. ASON
   RA levels do not reflect routing protocol levels (such as OSPF
   areas).

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   Successive hierarchical levels of RAs can be represented by separate
   instances of the protocol.

   Routing controllers (RCs) supporting RAs disseminate informtation
   downward and upward in this hierarchy. The vertical routing
   information dissemination mechanisms described in this section do not
   introduce or imply a new OSPF routing area hierarchy. RCs supporting
   RAs at multiple levels are structured as separate OSPF instances with
   routing information exchanges between levels described by import and
   export rules operating between OSPF instances.

   The implication is that an RC that performs import/export of routing
   information as described in this document does not implement an Area
   Border Router (ABR) functionality.

6.1 Import/Export Rules

   RCs supporting RAs disseminate information upward and downward in the
   hierarchy by importing/exporting routing information as Opaque TE
   LSAs (Opaque Type 1) of LS Type 10. The information that MAY be
   exchanged between adjacent levels includes the Router-Address, Link,
   and Node-Attribute top-level TLVs.

   The Opaque TE LSA import/export rules are governed as follows:

   - If the export target interface is associated with the same RA as is
     associated with the import interface, the Opaque LSA MUST NOT be
     imported.

   - If a match is found between the Advertising Router-ID in the
     header of the received Opaque TE LSA and one of the Router-IDs
     belonging to the RA of the export target interface, the Opaque LSA
     MUST NOT be imported.

   - If these two conditions are not met the Opaque TE LSA MAY be
     imported according to local policy. If imported, the LSA MAY be
     disseminated according to local policy. If disseminated, the normal
     OSPF flooding rules MUST be followed and the Advertising Router-ID
     MUST be set to the importing router's router-ID.

   The imported/exported routing information content MAY be transformed,
   e.g., filtered or aggregated, as long as the resulting routing
   information is consistent. In particular, when more than one RC is
   bound to adjacent levels and both are allowed to import/export
   routing information, it is expected that these transformation are
   performed in a consistent manner. Definition of these policy-based
   mechanisms is outside the scope of this document.



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   In practice, and in order to avoid scalability and processing
   overhead, routing information imported/exported downward/upward in
   the hierarchy is expected to include reachability information (see
   Section 3) and, upon strict policy control, link topology
   information.

6.2 Discovery and Selection

6.2.1 Upward Discovery and Selection

   In order to discover RCs that are capable to disseminate routing
   information up the routing hierarchy, the following Capability
   Descriptor bit [RFC4970] is defined:

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

   In the case that multiple RCs are advertized from the same RA with
   their U bit set, the RC with the highest Router-ID, among those RCs
   with the U bit set, SHOULD be selected as the RC for upward
   dissemination of routing information. The other RCs MUST 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. This mechanism prevents more than
   one RC advertizing routing information upward in the routing
   hierarchy from the same RA.

   Note that if the information to allow the selection of the RC that
   will be used to disseminate routing information up the hierarchy from
   a specific RA cannot be discovered automatically, it MUST be manually
   configured.

   Once an RC has been selected, it remains unmodified even if an RC
   with a higher Router-ID is introduced and advertizes its capability
   to disseminate routing information upward the adjacent level (i.e.,
   U-bit set). This hysteresis mechanism prevents from disturbing the
   upward routing information dissemination process in case, e.g., of
   flapping.

6.2.2 Downward Discovery and Selection

   The same discovery mechanism is used for selecting the RC responsible
   for dissemination of routing information downward in the hierarchy.
   However, an additional restriction MUST be applied such that the RC
   selection process takes into account that an upper level may be
   adjacent to one or more lower (RA) levels. For this purpose a
   specific TLV indexing the (lower) RA ID to which the RC's are capable
   of disseminating routing information is needed.


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   The Downstream Associated RA ID TLV is carried in the OSPF router
   information LSA [RFC4970]. The Length of this TLV is n x 4 octets.
   The Value field of this sub-TLV contains the list of Associated RA
   IDs. Each Associated RA ID value is encoded following the OSPF area
   ID (32 bits) encoding rules defined in [RFC2328].

   The format of the Downstream Associated RA ID TLV 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 (TBD)          |         Length (4 x n)        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Associated RA ID 1                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   //                             ...                             //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Associated RA ID n                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   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 [RFC4970] is defined, that MUST be advertised together with the
   Downstream Associated RA ID TLV:

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

   If multiple RCs are advertised for the same Associated RA ID, the RC
   with the highest Router ID, among the RCs with the D bit set, MUST be
   selected as the RC for downward dissemination of routing information.
   The other RCs for the same Associated RA ID MUST 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. This mechanism prevents from having more than one
   RC advertizing routing information downward the routing hierarchy.

   Note that if the information to allow the selection of the RC that
   will be used to disseminate routing information down the hierarchy to
   a specific RA 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 [RFC4970] and TE Node Capability Descriptor TLV


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   [RFC5073], MUST NOT be re-originated.

6.3 Loop Prevention

   When more than one RC is bound to an adjacent level of the hierarchy,
   and is configured or selected to redistribute routing information
   upward and downward, a specific mechanism is required to avoid
   looping of routing information. Looping is the re-introduction of
   routing information that has been advertized from the upper level
   back to the upper level. This specific case occurs, for example, when
   the RC advertizing routing information downward in the hierarchy is
   not the same one that advertizes routing upward in the hierarchy.

   When these conditions are met, it is necessary to have a means by
   which an RC receiving an Opaque TE LSA imported/exported downward by
   an RC associated to the same RA, does not import/export the content
   of this LSA back upward into the (same) upper level.

   Note that configuration and operational simplification can be
   obtained when both functionalities are configured on a single RC (per
   pair of adjacent levels) fulfilling both roles. Figure 1 provides an
   example where such simplification applies.

              ....................................................
              .                                                  .
              .            RC_5 ------------ RC_6                .
              .             |                 |                  .
              .             |                 |            RA_Y  .
     Upper    .           *********         *********            .
     Layer    ............* RC_1a *.........* RC_2a *.............
        __________________* |     *_________* |     *__________________
              ............* RC_1b *...   ...* RC 2b *.............
     Lower    .           *********  .   .  *********            .
     Layer    .             |        .   .    |                  .
              .  RA_Z       |        .   .    |            RA_X  .
              .            RC_3      .   .   RC_4                .
              .                      .   .                       .
              ........................   .........................

               Figure 1. Hierarchical Environment (Example)

   In this case, the procedure described in this section MAY be
   omitted, as long as these conditions are permanently guaranteed. In
   all other cases, without exception, the procedure described in this
   section MUST be applied.





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6.3.1 Associated RA ID

   We need some way of filtering the downward/upward re-originated
   Opaque TE LSA. Per [RFC5250], the information contained in Opaque
   LSAs may be used directly by OSPF. By adding the RA ID associated
   with the incoming routing information the loop prevention problem can
   be solved.

   This additional information, referred to as the Associated RA ID, MAY
   be carried in opaque LSAs that including any of the following top
   level LSAs:
   - the Router Address top level TLV
   - the Link top level TLV
   - the Node Attribute top level TLV.

   The Associated RA ID reflects the identifier of the area from which
   the routing information is received. For example, for a multi-level
   hierarchy, this identifier does not reflect the originating RA ID, it
   will reflect the RA from which the routing information is imported.

   The Length of the Associated RA ID TLV is 4 octets. The Value field
   of this sub-TLV contains the Associated RA ID. The Associated RA ID
   value is encoded following the OSPF area ID (32 bits) encoding rules
   defined in [RFC2328].

   The format of the Associated RA ID TLV is defined 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Type (TBD)          |           Length (4)          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Associated RA ID                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

6.3.2 Processing

   When fulfilling the rules detailed in Section 6.1 a given Opaque LSA
   is imported/exported downward or upward the routing hierarchy, the
   Associated RA ID TLV is added to the received opaque LSA list of TLVs
   such as to identify the area from which this routing information has
   been received.

   When the RC adjacent to the lower or upper level routing level
   receives this opaque LSA, the following rule is applied (in addition
   the rule governing the import/export of opaque LSAs as detailed in
   Section 6.1).



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   - If a match is found between the Associated RA ID of the received
     Opaque TE LSA and the RA ID belonging to the area of the export
     target interface, the Opaque TE LSA MUST NOT be imported.

   - Otherwise, this opaque LSA MAY be imported and disseminated
     downward or upward the routing hierarchy following the OSPF
     flooding rules.

   This mechanism ensures that no race condition occurs when the
   conditions depicted in Figure 2 are met.

                           RC_5 ------------- RC_6
                            |                 |
                            |                 |            RA_Y
     Upper                *********         *********
     Layer    ............* RC_1a *.........* RC_2a *.............
        __________________* |     *_________* |     *__________________
              ............* RC_1b *.........* RC 2b *.............
     Lower                *********         *********
     Layer                  |                 |
                            |                 |            RA_X
                           RC_3 --- . . . --- RC_4

               Figure 2. Race Condition Prevention (Example)

   Assume that RC_1b is configured for exporting routing information
   upward toward RA_Y (upward the routing hierarchy) and that RC_2a is
   configured for exporting routing information toward RA_X (downward
   the routing hierarchy).

   Assumes that routing information advertised by RC_3 would reach
   RC_4 faster across RA_Y through hierarchy.

   If RC_2b is not able to prevent from importing that information,
   RC_4 may receive that information before the same advertisement
   would propagate in RA_X (from RC_3) to RC_4. For this purpose RC_1a
   inserts the Associated RA X to the imported routing information
   from RA_X. Because RC_2b finds a match between the Associated RA
   ID (X) of the received Opaque TE LSA and the ID (X) of the RA of the
   export target interface, this LSA MUST NOT be imported.

6.4 Resiliency

   OSPF creates adjacencies between neighboring routers for the purpose
   of exchanging routing information. After a neighbor has been
   discovered, bidirectional communication is ensured, and a routing
   adjacency is formed between RCs, loss of communication may result in
   partitioned OSPF areas and so in partitioned RAs.


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   Consider for instance (see Figure 2.) the case where RC_1a and RC_1b
   is configured for exchanging routing information downward and upward
   RA_Y, resp., and that RC_2a and RC_2b are not configured for
   exchanging routing any routing information toward RA_X. If the
   communication between RC_1a and RC_2a is broken (due, e.g., to RC_5 -
   RC_6 communication failure), RA_Y could be partitioned.

   In these conditions, it is RECOMMENDED that RC_2a be re-configurable
   such as to allow for exchanging routing information downward to RA_X.
   This reconfiguration MAY be performed manually or automatically. In
   the latter cases, automatic reconfiguration uses the mechanism
   described in Section 6.2 (forcing MaxAge of the corresponding opaque
   LSA information in case the originating RC becomes unreachable).
   Manual reconfiguration MUST be supported.

6.5 Neighbor Relationship and Routing Adjacency

   It is assumed that (point-to-point) IP control channels are
   provisioned/configured between RCs belonging to the same routing
   level. Provisioning/configuration techniques are outside the scope
   of this document.

   Once established, the OSPF Hello Protocol is responsible for
   establishing and maintaining neighbor relationships. This protocol
   also ensures that communication between neighbors is bidirectional.
   Routing adjacency can subsequently be formed between RCs following
   mechanisms defined in [RFC2328].

6.6 Reconfiguration

   This section details the RA ID reconfiguration steps.

   Reconfiguration of the RA ID occurs when the RA ID is modified
   e.g. from value Z to value X or Y (see Figure 2.).

   The process of reconfiguring the RA ID involves:

   - Disable the import/export of routing information from the upper
     and lower level (to prevent any LS information update).

   - Change the RA ID of the local level RA from e.g. Z to X or Y.
     Perform an LSDB checksum on all routers to verify that LSDB are
     consistent.

   - Enable import of upstream and downstream routing information such
     as to re-synchronize local level LSDB from any LS information that
     may have occurred in an upper or a lower routing level.



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   - Enable export of routing information downstream such as to re-sync
     the downstream level with the newly reconfigured RA ID (as part of
     the re-advertised Opaque TE LSA).

   - Enable export of routing information upstream such as to re-sync
     the upstream level with the newly reconfigured RA ID (as part of
     the re-advertised Opaque TE LSA).

   Note that the re-sync operation needs to be carried out only between
   the directly adjacent upper and lower routing level.

7. OSPFv2 Extensions

7.1 Compatibility

   Extensions specified in this document are associated to the:

   1. Opaque Traffic Engineering LSA (Type 1) defined in [RFC3630]:

      - Router Address top level TLV (Type 1):

        - Associated RA ID sub-TLV: optional sub-TLV for loop avoidance.

      - 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.

        - Associated RA ID sub-TLV: optional sub-TLV for loop avoidance.

     - Node Attribute top level TLV (Type TBD by IANA):

       - Node IPv4 Local Prefix sub-TLV: optional sub-TLV for IPv4
         reachability advertisement.

       - Node IPv6 Local Prefix sub-TLV: optional sub-TLV for IPv6
         reachability advertisement.

       - Local TE Router-ID sub-TLV: optional sub-TLV for scoping
         reachability per TE Router-ID.

       - Associated RA ID sub-TLV: optional sub-TLV for loop avoidance.

   2. Opaque Router Information LSA (Type 4) defined in [RFC4970]:

      - Router Information Capability Descriptor TLV (Type 1).

        - U bit in Capability Descriptor TLV (bit position TBD by IANA).


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        - D bit in Capability Descriptor TLV (bit position TBD by IANA).

      - Router Downstream Associated RA ID TLV (Type - see Section
        9.2.2).

7.2 Scalability

   - Routing information exchange upward/downward in the hierarchy
     between adjacent RAs SHOULD by default be limited to reachability
     information. In addition, several transformations such as prefix
     aggregation are RECOMMENDED when allowing decreasing the amount of
     information imported/exported by a given RC without impacting
     consistency.

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

   - The number of routing levels MUST be maintained under strict policy
     control.

8. Security Considerations

   This document specifies the contents and processing of Opaque LSAs
   in OSPFv2 [RFC2328]. Opaque TE and RI LSAs defined in this document
   are not used for SPF computation, and so have no direct effect on IP
   routing. Additionally, ASON routing domains are delimited by the
   usual administrative domain boundaries.

   Any mechanisms used for securing the exchange of normal OSPF LSAs
   can be applied equally to all Opaque TE and RI LSAs used in the ASON
   context. In order to be secured against passive attacks and provide
   significant protection against active attacks, mechanisms to
   authenticate OSPFv2 LSA exchanges shall be used for Opaque LSAs such
   as OSPF cryptographic authentication [RFC2328] and [OSPF-CA]. The
   latter defines a mechanism for authenticating OSPF packets by making
   use of the HMAC algorithm in conjunction with the SHA family of
   cryptographic hash functions.

   [RFC2154] adds i) digital signatures to authenticate OSPF LSA data,
   ii) certification mechanism for distribution of routing information,
   and iii) use a neighbor-to-neighbor authentication algorithm to
   protect local OSPFv2 protocol exchanges.






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9. IANA Considerations

9.1 Sub-TLVs for the OSPF Opaque TE LSA

   IANA manages a registry of sub-TLVs carried in traffic engineering
   TLVs in the Opaque TE LSA. This registry is found as the "Types for
   sub-TLVs of TE Link TLV" subregistry of the "Open Shortest Path First
   (OSPF) Traffic Engineering TLVs" registry.

   IANA is requested to make allocations from this registry for the
   following new sub-TLVs:

   - Associated RA ID sub-TLV: optional sub-TLV (see Section 6.3.1)

   - Downstream Associated RA ID sub-TLV: optional sub-TLV (see
     Section 6.2)

   - Local TE Router ID sub-TLV: optional sub-TLV (see Section 5.3)

   - Local and Remote TE Router ID sub-TLV: optional sub-TLV (see
     Section 5.2)

   - Node IPv4 Local Prefix sub-TLV: optional sub-TLV (see Section 3.1)

   - Node IPv6 Local Prefix sub-TLV: optional sub-TLV (see Section 4.2)

   The additions to the sub-registry should read as follows:

   Value        Sub-TLV                                       Reference
   -----------  --------------------------------------------  ----------
   TBD          Associated RA ID                              [This.ID]
   TBD          Downstream Associated RA ID                   [This.ID]
   TBD          Local TE Router ID                            [This.ID]
   TBD          Local and Remote TE Router ID                 [This.ID]
   TBD          Node IPv4 Local Prefix                        [This.ID]
   TBD          Node IPv6 Local Prefix                        [This.ID]

9.2 OSPF RI LSA

9.2.1 RI Capability Bits

   IANA maintains the "Open Shortest Path First v2 (OSPFv2) Parameters"
   registry with a subregistry called "OSPF Router Informational
   Capability Bits".

   IANA is requested to allocate two new bits as follows:

   - U bit (see Section 6.2.1)
   - D bit (see Section 6.2.2)

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   The registry entries should look as follows:

   Bit       Capabilities                            Reference
   --------  --------------------------------------  ---------
   TBD       Upward routing dissemination capable    [This.ID]
   TBD       Downward routing dissemination capable  [This.ID]

9.2.2 RI LSA TLVs

   IANA maintains the "Open Shortest Path First v2 (OSPFv2) Parameters"
   registry with a subregistry called "OSPF Router Information (RI)
   TLVs".

   An Experimental TLV is required as follows:

   - Downstream Associated RA ID TLV (see Section 7.1).

   The registry states that Experimental allocations are not tracked by
   IANA. Therefore, this document assigns as follows:

   Type Value   Capabilities                            Reference
   -----------  --------------------------------------  ---------
   32781        Downstream Associated RA ID             [This.ID]

10. References

10.1 Normative References

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

   [RFC2154]    Murphy, S., Badger, M. and B. Wellington, "OSPF with
                Digital Signatures", RFC 2154, June 1997.

   [RFC2328]    J. Moy, "OSPF Version 2", RFC 2328, STD 54, April 1998.

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

   [RFC3945]    E.Mannie, Ed., "Generalized Multi-Protocol Label
                Switching (GMPLS) Architecture", RFC 3945, October 2004.

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

   [RFC4203]    K. Kompella (Editor) et al., "OSPF Extensions in
                Support of Generalized Multi-Protocol Label Switching
                (GMPLS)," RFC 4203, October 2005.


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   [RFC4970]    A. Lindem et al., "Extensions to OSPF for Advertising
                Optional Router Capabilities", RFC 4970, July 2007.

   [RFC5250]    Berger, L., Bryskin, I., Zinin, A., and R. Coltun, "The
                OSPF Opaque LSA Option", RFC 5250, July 2008.

   [RFC5340]    Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
                for IPv6", RFC 5340, July 2008.

   [OSPF-NODE]  R. Aggarwal and K. Kompella, "Advertising a Router's
                Local Addresses in OSPF TE Extensions", draft-ietf-ospf-
                te-node-addr, work in progress.

10.2 Informative References

   [RFC4258]    D.Brungard (Ed.) et al. "Requirements for Generalized
                MPLS (GMPLS) Routing for Automatically Switched Optical
                Network (ASON)," RFC 4258, November 2005.

   [RFC4652]    D.Papadimitriou (Ed.) et al. "Evaluation of existing
                Routing Protocols against ASON Routing Requirements",
                RFC 4652, October 2006.

   [RFC5073]    J.P.Vasseur et al., "Routing extensions for discovery of
                Traffic Engineering Node Capabilities", RFC 5073,
                December 2007.

   [OSPF-CA]    Bhatia, M., Manral, V., White, R., and M., Barnes, "OSPF
                HMAC-SHA Cryptographic Authentication", draft-ietf-ospf-
                hmac-sha, work in progress.

   For information on the availability of ITU Documents, please see
   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).





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11. Author's Address

   Dimitri Papadimitriou
   Alcatel-Lucent Bell
   Copernicuslaan 50
   B-2018 Antwerpen
   Belgium
   Phone: +32 3 2408491
   EMail: dimitri.papadimitriou@alcatel-lucent.be

Acknowledgements

   The authors would like to thank Dean Cheng, Acee Lindem, Pandian
   Vijay, Alan Davey, Adrian Farrel, and Deborah Brungard for their
   useful comments and suggestions.

   Question 14 of Study Group 15 of the ITU-T provided useful and
   constructive input.
































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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.

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

   Copyright (C) The IETF Trust (2008).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 78, and except as set forth therein, the authors
   retain all their rights.

   This document and the information contained herein are provided on an
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
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D.Papadimitriou - Expires April 2009                           [Page 27]


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