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Versions: (draft-farrel-ccamp-inter-domain-framework) 00 01 02 03 04 05 06 RFC 4726

Network Working Group                                      Adrian Farrel
IETF Internet Draft                                    Olddog Consulting
Proposed Status: Informational
Expires: August 2005                               Jean-Philippe Vasseur
                                                     Cisco Systems, Inc.

                                                          Arthi Ayyangar
                                                        Juniper Networks

                                                           February 2005

          A Framework for Inter-Domain MPLS Traffic Engineering
             draft-ietf-ccamp-inter-domain-framework-01.txt

Status of this Memo

   This document is an Internet-Draft and is subject to all provisions
   of Section 3 of RFC 3667. By submitting this Internet-Draft, each
   author represents that any applicable patent or other IPR claims of
   which he or she is aware have been or will be disclosed, and any of
   which he or she become aware will be disclosed, in accordance with
   RFC 3668.

   Internet-Drafts are working documents of the Internet Engineering
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Copyright Notice

   Copyright (C) The Internet Society (2005). All Rights Reserved.

Abstract

   This document provides a framework for establishing and controlling
   Multiprotocol Label Switching (MPLS) and Generalized MPLS (GMPLS)
   Label Switched Paths (LSPs) in multi-domain networks.

   For the purposes of this document, a domain is considered to be any
   collection of network elements within a common sphere of address
   management or path computational responsibility. Examples of such
   domains include IGP areas and Autonomous Systems.

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Contents

   1. Introduction ...............................................
     1.1. Nested Domains .........................................
     1.2. Conventions used in this document ......................
   2. Signaling Options ..........................................
     2.1. LSP Nesting ............................................
     2.2. Contiguous LSP .........................................
     2.3. LSP Stitching ..........................................
     2.4. Hybrid Methods .........................................
     2.5. Control of Downstream Choice of Signaling Method ....... x
   3. Path Computation Techniques ................................
     3.1. Management Configuration ...............................
     3.2. Head End Computation ...................................
       3.2.1. Multi-Domain Visibility Computation ................
       3.2.2. Partial Visibility Computation .....................
       3.2.3. Local Domain Visibility Computation ................
     3.3. Domain Boundary Computation ............................
     3.4. Path Computation Element ...............................
       3.4.1. Multi-Domain Visibility Computation ................
       3.4.2. Path Computation Use of PCE When Preserving
              Confidentiality ....................................
       3.4.3. Per-Domain Computation Servers .....................
     3.5. Optimal Path Computation ...............................
   4. Distributing Reachability and TE Information ...............
   5. Comments on Advanced Functions .............................
     5.1. LSP Re-Optimization ....................................
     5.2. LSP Setup Failure ......................................
     5.3. LSP Repair .............................................
     5.4. Fast Reroute ...........................................
     5.5. Comments on Path Diversity .............................
     5.6. Domain-Specific Constraints ............................
     5.7. Policy Control .........................................
     5.8. Inter-domain OAM .......................................
     5.9. Point-to-Multipoint ....................................
     5.10. Applicability to Non-Packet Technologies ..............
   6. Security Considerations ....................................
   7. IANA Considerations ........................................
   8. Acknowledgements ...........................................
   9. Intellectual Property Considerations .......................
   10. Normative References ......................................
   11. Informational References ..................................
   12. Authors' Addresses ........................................
   13. Full Copyright Statement ..................................







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1. Introduction

   The Traffic Engineering Working Group has developed requirements for
   inter-area and inter-AS MPLS Traffic Engineering in [INTER-AREA] and
   [INTER-AS].

   Various proposals have subsequently been made to address some or all
   of these requirements through extensions to the RSVP-TE and IGP
   (ISIS, OSPF) protocols and procedures.

   This document introduces the techniques for establishing TE LSPs
   across multiple domains. The functional components of these
   techniques are separated into the mechanisms for discovering
   reachability and TE information, for computing the paths of LSPs, and
   for signaling the LSPs. Note that the aim of this document is not to
   detail each of those techniques which are covered in separate
   documents, but rather to propose a framework for inter-domain MPLS
   Traffic Engineering.

   Note that in the remainder of this document, the term 'MPLS Traffic
   Engineering' is used equally to apply to MPLS and GMPLS traffic
   engineering in packet and non-packet environments.

   For the purposes of this document, a domain is considered to be any
   collection of network elements within a common sphere of address
   management or path computational responsibility. Examples of such
   domains include IGP areas and Autonomous Systems. However, domains of
   computational responsibility may also exist as sub-domains of areas
   or ASs. Wholly or partially overlapping domains are not within the
   scope of this document.

1.1. Nested Domains

   Nested domains are outside the scope of this document. It may be that
   some domains that are nested administratively or for the purposes of
   address space management can be considered as adjacent domains for
   the purposes of this document, however the fact that the domains are
   nested is then immaterial.

   In the context of MPLS TE, domain A is considered to be nested within
   domain B if domain A is wholly contained in Domain B, and domain B is
   fully or partially aware of the TE characteristics and topology of
   domain A.

   For further consideration of nested domains see [MRN]






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1.2. 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].

2. Signaling Options

   Three distinct options for signaling TE LSPs across multiple domains
   are identified. The choice of which options to use may be influenced
   by the path computation technique used (see section 3), although some
   path computation techniques may apply to multiple TE LSP types. The
   choice may further depend on the application to which the TE LSPs are
   put and the nature, topology and switching capabilities of the
   network.

   A comparison of the usages of the different signaling options is
   beyond the scope of this document and should be the subject of a
   separate applicability statement.

2.1. LSP Nesting

   Forwarding Adjacencies (FAs) are introduced and explained in detail
   in [HIER]. No further description is necessary in this document.

   FAs can be used in support of inter-domain TE LSPs. In particular, an
   FA may be used to achieve connectivity between any pair of LSRs
   within a domain. The ingress and egress of the FA LSP could be the
   edge nodes of the domain in which case connectivity is achieved
   across the entire domain, or they could be any other pair of LSRs in
   the domain.

   The technique of carrying one TE LSP within another is termed LSP
   nesting. An FA may provide a TE LSP tunnel to transport (i.e. nest)
   multiple TE LSPs along a common part of their paths. Alternatively, a
   TE LSP may carry (i.e. nest) a single LSP in a one-to-one mapping.

   The signaling trigger for the establishment of an FA LSP may be the
   receipt of a signaling request for the TE LSP that it will carry, or
   may be a management action to 'pre-engineer' a domain to be crossed
   by TE LSPs that would be used as FAs by the traffic that has to
   traverse the domain. Furthermore, the mapping (inheritance rules)
   between attributes of the nested and FA LSPs (including bandwidth)
   may be statically pre-configured or, for on-demand FA LSPs, may be
   dynamic according to the properties of the nested LSPs.

   Note that a hierarchical LSP may be constructed to span multiple
   domains or parts of domains. However, how or whether such an LSP
   could be advertised as an FA that spans domains is open for study.
   The end points of a hierarchical LSP are not necessarily on domain

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   boundaries, so nesting is not limited to domain boundaries.

   Note also that the IGP/EGP routing topology is maintained unaffected
   by the LSP connectivity and TE links introduced by FA LSPs. That is,
   the routing protocols do not exchange messages over the FA LSPs, and
   such LSPs do not create routing adjacencies between routers.

   During the operation of establishing a nested LSP that uses a
   hierarchical LSP, the SENDER_TEMPLATE and SESSION objects remain
   unchanged along the entire length of the nested LSP.

2.2. Contiguous LSP

   A single contiguous LSP is established from ingress to egress in a
   single signaling exchange. No further LSPs are required to be
   established to support this LSP. Signaling occurs between adjacent
   neighbors only (no tunneling), and hop-by-hop signaling is used.

2.3. LSP Stitching

   LSP Stitching is described in [STITCH].

   In the LSP stitching model separate LSPs (referred to as a TE LSP
   segments) are established and are "stitched" together in the data
   plane so that a single end-to-end label switched path is achieved.
   The distinction is that the component LSP segments are signaled as
   distinct TE LSPs in the control plane. Each signaled TE LSP segment
   has a different source and destination.

   LSP stitching can be used in support of inter-domain TE LSPs. In
   particular, an LSP segment may be used to achieve connectivity
   between any pair of LSRs within a domain. The ingress and egress of
   the LSP segment could be the edge nodes of the domain in which case
   connectivity is achieved across the entire domain, or they could be
   any other pair of LSRs in the domain.

   The signaling trigger for the establishment of a TE LSP segment may
   be the establishment of the previous TE LSP segment, the receipt of
   setup request for TE LSP that it plans to stitch to a local TE LSP
   segment, or may be a management action.

   LSP segments may be managed as FAs and advertised as TE links.

2.4. Hybrid Methods

   There is nothing to prevent the mixture of signaling methods
   described above when establishing a single, end-to-end, inter-domain
   TE LSP. It may be desirable in this case for the choice of the
   various methods to be indicated along the path perhaps through the
   RRO.

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   If there is a desire to restrict which methods are used, this MUST be
   signaled as described in the next section.

2.5. Control of Downstream Choice of Signaling Method

   Notwithstanding the previous section, an ingress LSR MAY wish to
   restrict the signaling methods applied to a particular LSP at domain
   boundaries across the network. Such control, where it is required,
   may be achieved by the definition of appropriate new flags in the
   SESSION-ATTRIBUTE object or the Attributes Flags TLV of the
   LSP_ATTRIBUTES object [ATTRIB]. Before defining a mechanism to
   provide this level of control, the functional requirement to control
   the way in which the network delivers a service must be established
   and due consideration must be given to the impact on
   interoperability.

3. Path Computation Techniques

   The discussion of path computation techniques within this document is
   limited significantly to the determination of where computation may
   take place and what components of the full path may be determined.

   The techniques used are closely tied to the signaling methodologies
   described in the previous section in that certain computation
   techniques may require the use of particular signaling approaches and
   vice versa.

   Any discussion of the appropriateness of a particular path
   computation technique in any given circumstance is beyond the scope
   of this document and should be described in a separate applicability
   statement.

   Path computation algorithms are firmly out of scope of this document.

3.1. Management Configuration

   Path computation may be performed by offline tools or by a network
   planner. The resultant path may be supplied to the ingress LSR as
   part of the TE LSP or service request, and encoded by the ingress LSR
   as an ERO on the Path message that is sent out.

   There is no reason why the path provided by the operator should not
   span multiple domains if the relevant information is available to the
   planner or the offline tool. The definition of what information is
   needed to perform this operation and how that information is
   gathered, is outside the scope of this document.





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3.2. Head End Computation

   The head end, or ingress, LSR may assume responsibility for path
   computation when the operator supplies part or none of the explicit
   path. The operator MUST, in any case, supply at least the destination
   address (egress) of the LSP.

3.2.1. Multi-Domain Visibility Computation

   If the ingress has sufficient visibility of the topology and TE
   information for all of the domains across which it will route the LSP
   to its destination then it may compute and provide the entire path.
   The quality of this path (that is, its optimality as discussed in
   section 3.5) is best if the ingress has full visibility into all
   relevant domains rather than just sufficient visibility to provide
   some path to the destination.

   Extreme caution must be exercised in consideration of the
   distribution of the requisite TE information. See section 4.

3.2.2. Partial Visibility Computation

   It may be that the ingress does not have full visibility of the
   topology of all domains, but does have information about the
   connectedness of the domains and the TE resource availability across
   the domains. In this case, the ingress is not able to provide a fully
   specified strict explicit path from ingress to egress. However, the
   ingress can supply an explicit path that comprises:
   - explicit hops from ingress to the local domain boundary
   - loose hops representing the domain entry points across the network
   - a loose hop identifying the egress.

   Alternatively, the explicit path may be expressed as:
   - explicit hops from ingress to the local domain boundary
   - strict hops giving abstract nodes representing each domain in turn
   - a loose hop identifying the egress.

   These two explicit path formats may be mixed.

   This form of explicit path relies on some further computation
   technique being applied at the domain boundaries. See section 3.3.

   As with the multi-domain visibility option, extreme caution must be
   exercised in consideration of the distribution of the requisite TE
   information. See section 4.






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3.2.3. Local Domain Visibility Computation

   A final possibility for ingress-based computation is that the ingress
   LSR has visibility only within its own domain, and connectivity
   information only as far as determining one or more domain exit points
   that may be suitable for carrying the LSP to its egress.

   In this case the ingress builds an explicit path that comprises just:
   - explicit hops from ingress to the local domain boundary
   - a loose hop identifying the egress.

3.3. Domain Boundary Computation

   If the partial explicit path methods described in sections 3.2.2 or
   3.2.3 are applied then the LSR at each domain boundary is responsible
   for ensuring that there is sufficient path information added to the
   Path message to carry it at least to the next domain boundary (that
   is, out of the new domain).

   If the LSR at the domain boundary has full visibility to the egress
   then it can supply the entire explicit path. Note however, that the
   ERO processing rules of [RFC3209] state that it SHOULD only update
   the ERO as far as the next specified hop (that is, the next domain
   boundary if one was supplied in the original ERO) and, of course,
   MUST NOT insert ERO subobjects immediately before a strict hop.

   If the LSR at the domain boundary has only partial visibility (using
   the definitions of section 3.2.2) it will fill in the path as far as
   the next domain boundary, and will supply further domain/domain
   boundary information if not already present in the ERO.

   If the LSR at the domain boundary has only local visibility into the
   immediate domain it will simply add information to the ERO to carry
   the Path message as far as the next domain boundary.

3.4. Path Computation Element

   The computation techniques in sections 3.2 and 3.3 rely on topology
   and TE information being distributed to the ingress LSR and those
   LSRs at domain boundaries. These LSRs are responsible for computing
   paths. Note that there may be scaling concerns with distributing the
   required information - see section 4.

   An alternative technique places the responsibility for path
   computation with a Path Computation Element (PCE) [PCE]. There may be
   either a centralized PCE, or multiple PCEs (each having local
   visibility and collaborating in a distributed fashion to compute an
   end-to-end path) across the entire network and even within any one
   domain. The PCE may collect topology and TE information from the same


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   sources as would be used by LSRs in the previous paragraph, or though
   other means.

   Each LSR called upon to perform path computation (and even the
   offline management tools described in section 3.1) may abdicate the
   task to a PCE of its choice. The selection of PCE(s) may be driven by
   static configuration or the dynamic discovery by means of IGP or BGP
   extensions.

3.4.1. Multi-Domain Visibility Computation

   A PCE may have full visibility, perhaps through connectivity to
   multiple domains. In this case it is able to supply a full explicit
   path as in section 3.2.1.

3.4.2. Path Computation Use of PCE When Preserving Confidentiality

   Note that although a centralized PCE or multiple collaborative PCEs
   may have full visibility into one or more domains, it may be
   desirable (e.g to preserve confidentiality) that the full path is not
   provided to the ingress LSR. Instead, a partial path is supplied (as
   in section 3.2.2 or 3.2.3) and the LSRs at each domain boundary are
   required to make further requests for each successive segment of the
   path.

   In this way an end-to-end path may be computed using the full network
   capabilities, but confidentiality between domains may be preserved.
   Optionally, the PCE(s) may compute the entire path at the first
   request and hold it in storage for subsequent requests, or it may
   recompute the best path on each request or at regular intervals.

   It may be the case that the centralized PCE or the collaboration
   between PCEs may define a trust relationship greater than that
   normally operational between domains.

3.4.3. Per-Domain Computation Servers

   A third way that PCEs may be used is simply to have one (or more) per
   domain. Each LSR within a domain that wishes to derive a path across
   the domain may consult its local PCE.

   This mechanism could be used for all path computations within the
   domain, or specifically limited to computations for LSPs that will
   leave the domain where external connectivity information can then be
   restricted to just the PCE.






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3.5. Optimal Path Computation

   An optimal route might be defined as the route that would be computed
   in the absence of domain boundaries. Another constraint to the
   definition of 'optimal' might be to reduce or limit the number of
   domains crossed by the LSP. It is easy to construct examples
   that show that partitioning a network into domains, and the resulting
   loss or aggregation of routing information may lead to the
   computation of routes that are other than optimal. It is impossible
   to guarantee optimal routing in the presence of aggregation /
   abstraction / summarization of routing information.

   It is beyond the scope of this document to define what is an optimum
   path for an inter-domain TE LSP. This debate is abdicated in favor of
   requirements documents and applicability statements. Note, however,
   that the meaning of certain computation metrics may differ between
   domains (see section 5.6).

4. Distributing Reachability and TE Information

   The path computation techniques described in the previous section
   make certain demands upon the distribution of reachability
   information and the TE capabilities of nodes and links within domains
   as well as the TE connectivity across domains.

   Currently, TE information is distributed within domains by additions
   to IGPs [RFC3630], [RFC3784].

   In cases where two domains are interconnected by one or more links
   (that is, the domain boundary falls on a link rather than on a node),
   there SHOULD be a mechanism to distribute the TE information
   associated with the inter-domain links to the corresponding domains.
   This would facilitate better path computation and reduce TE-related
   crankbacks on these links.

   Where a domain is a subset of an IGP area, filtering of TE
   information may be applied at the domain boundary. This filtering may
   be one way, or two way.

   Where information needs to reach a PCE that spans multiple domains,
   the PCE may snoop on the IGP traffic in each domain, or play an
   active part as an IGP-capable node in each domain. The PCE might also
   receive TEDB updates from a proxy within the domain.

   It could be possible that an LSR that performs path computation (for
   example, an ingress LSR) obtains the topology and TE information of
   not just its own domain, but other domains as well. This information
   may be subject to filtering applied by the advertising domain (for
   example, the information may be limited to FAs across other domains,
   or the information may be aggregated or abstracted).

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   Where any cross-domain reachability and TE information needs to be
   advertised, consideration must be given to TE extensions to BGP, and
   how these may be fed to the IGPs. Techniques for inter-domain TE
   aggregation are also for further study. However, it must be noted
   that any extensions that cause a significant increase in the amount
   of processing (such as aggregation computation) at domain boundaries,
   or a significant increase in the amount of information flooded (such
   as detailed TE information) need to be treated with extreme caution
   and compared carefully with the scaling requirements expressed in
   [INTER-AREA] and [INTER-AS].

5. Comments on Advanced Functions

   This section provides some non-definitive comments on the constraints
   placed on advanced MPLS TE functions by inter-domain MPLS. It does
   not attempt to state the implications of using one inter-domain
   technique or another. Such material is deferred to appropriate
   applicability statements where statements about the capabilities of
   existing or future signaling, routing and computation techniques to
   deliver the functions listed should be made.

5.1. LSP Re-Optimization

   Re-optimization is the process of moving a TE LSP from one path to
   another, more preferable path (where no attempt is made in this
   document to define 'preferable' as no attempt was made to define
   'optimal'). Make-before-break techniques are usually applied to
   ensure that traffic is disrupted as little as possible. The Shared
   Explicit style is usually used to avoid double booking of network
   resources.

   Re-optimization may be available within a single domain.
   Alternatively, re-optimization may involve a change in route across
   several domains or might involve a choice of different transit
   domains.

   Re-optimization requires that all or part of the path of the LSP be
   re-computed. The techniques used may be selected as described in
   section 3, and this will influence whether the whole or part of the
   path is re-optimized.

   The trigger for path computation and re-optimization may be an
   operator request, a timer, or information about a change in
   availability of network resources. This trigger MUST be applied to
   the point in the network that requests re-computation and controls
   re-optimization and may require additional signaling.

   Note also that where multiple diverse paths are applied end-to-end
   (i.e. not simply within protection domains - see section 5.5) the
   point of calculation for re-optimization (whether it is PCE, ingress,

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   or domain entry point) needs to know all such paths before attempting
   re-optimization of any one path.

5.2. LSP Setup Failure

   When an inter-domain LSP setup fails in some domain other than the
   first, various options are available for reporting and retrying the
   LSP.

   In the first instance, a retry may be attempted within the domain
   that contains the failure. That retry may be attempted by nodes
   wholly within the domain, or the failure may be referred back to the
   LSR at the domain boundary.

   If the failure cannot be bypassed within the domain where the failure
   occurred (perhaps there is no suitable alternate route, perhaps
   rerouting is not allowed by domain policy, or perhaps the Path
   message specifically bans such action), the error MUST be reported
   back to the previous or head-end domain.

   Subsequent repair attempts may be made by domains further upstream,
   but will only be properly effective if sufficient information about
   the failure and other failed repair attempts is also passed back
   upstream [CRANKBACK]. Note that there is a tension between this
   requirement and that of confidentiality although crankback
   aggregation may be applicable at domain boundaries.

   Further attempts to signal the failed LSP may apply the information
   about the failures as constraints to path computation, or may signal
   them as specific path exclusions [EXCLUDE].

   When requested by signaling, the failure may also be systematically
   reported to the head-end LSR.

5.3. LSP Repair

   An LSP that fails after it has been established may be repaired
   dynamically by re-routing. The behavior in this case is either like
   that for re-optimization, or for handling setup failures (see
   previous two sections).

   Fast Reroute may also be used (see below).

5.4. Fast Reroute

   MPLS Traffic Engineering Fast Reroute ([FRR]) defines local
   protection schemes intended to provide fast recovery (in 10s of
   msecs) of fast-reroutable TE LSPs upon link/SRLG/Node failure. A
   backup TE LSP is configured and signaled at each hop, and activated
   upon detecting or being informed of a network element failure. The

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   node immediately upstream of the failure (called the PLR - Point of
   Local Repair) reroutes the set of protected TE LSPs onto the
   appropriate backup tunnel(s) and around the failed resource.

   In the context of inter-domain TE, there are several different
   failure scenarios that must be analyzed. Provision of suitable
   solutions may be further complicated by the fact that [FRR] specifies
   two distinct modes of operation referred to as the "one to one mode"
   and the "facility back-up mode".

   The failure scenarios specific to inter-domain TE are as follows:

   - Failure of a domain edge node that is present in both domains.
     There are two sub-cases:

     - The PLR and the MP are in the same domain

     - The PLR and the MP are in different domains.

   - Failure of a domain edge node that is only present in one of the
     domains.

   - Failure of an inter-domain link.

   The techniques that must be employed to use Fast Reroute for the
   different methods of signaling LSPs identified in section 2 differ
   considerably. These should be explained further in applicability
   statements of, in the case, of a change in base behavior, in
   implementation guidelines specific to the signaling techniques.

   Note that after local repair has been performed, it may be desirable
   to re-optimize the LSP (see section 5.1). If the point of
   re-optimization (for example the ingress LSR) lies in a different
   domain to the failure, it may rely on the delivery of a PathErr or
   Notify message to inform it of the local repair event.

   It is important to note that Fast Reroute techniques are only
   applicable to packet switching networks because other network
   technologies cannot apply label stacking within the same switching
   type. Segment protection [SEG-PROT] provides a suitable alternative
   that is applicable to packet and non-packet networks.

5.5. Comments on Path Diversity

   Diverse paths may be required in support of load sharing and/or
   protection. Such diverse paths may be required to be node diverse,
   link diverse, fully path diverse (that is, link and node diverse), or
   SRLG diverse.



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   Diverse path computation is a classic problem familiar to all graph
   theory majors. The problem is compounded when there are areas of
   'private knowledge' such as when domains do not share topology
   information. The problem is generally considered to be easier and
   more efficient when the diverse paths can be computed
   'simultaneously' on the fullest set of information. That being said,
   various techniques (out of the scope of this document) exist to
   ensure end-to-end path diversity across multiple domains.

   Many network technologies utilize 'protection domains' because they
   fit well with the capabilities of the technology. As a result, many
   domains are operated as protection domains. In this model, protection
   paths converge at domain boundaries.

   Note that the question of SRLG identification is not yet fully
   answered. There are two classes of SRLG:

   - those that indicate resources that are all contained witin one
     domain

   - those that span domains.

   The former might be identified using a combination of domain ID and
   an SRLG ID that is administered by the domain. The latter requires
   a wider scope to the SRLG ID, and it is not clear how this would be
   administered.

5.6. Domain-Specific Constraints

   While the meaning of certain constraints, like bandwidth, can be
   assumed to be constant across different domains, other TE constraints
   (such as resource affinity, color, metric, priority, etc.) may have
   different meanings in different domains and this may impact the
   ability to support DiffServ-aware MPLS, or to manage pre-emption.

   In order to achieve consistent meaning and LSP establishment, this
   fact must be considered when performing constraint-based path
   computation or when signaling across domain boundaries.

   A mapping function can be derived for most constraints based on
   policy agreements between the Domain administrators. The details of
   such a mapping function are outside the scope of this document, but
   it is important to note that the default behavior MUST either be
   that a constant mapping is applied or that any requirement to apply
   these constraints across a domain boundary must fail in the absence
   of explicit mapping rules.





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5.7. Policy Control

   Domain boundaries are natural points for policy control. There is
   little to add on this subject except to note that a TE LSP that
   cannot be established on a path through one domain because of a
   policy applied at the domain boundary, may be satisfactorily
   established using a path that avoids the demurring domain. In any
   case, when a TE LSP signaling attempt is rejected due to
   non-compliance with some policy constraint, this SHOULD be reflected
   to the ingress LSR.

5.8. Inter-domain OAM

   Some elements of OAM may be intentionally confined within a domain.
   Others (such as end-to-end liveness and connectivity testing) clearly
   need to span the entire multi-domain TE LSP. Where issues of
   confidentiality are strong, collaboration between PCEs or domain
   boundary nodes might be required in order to provide end-to-end OAM.

   The different signaling mechanisms described above may need
   refinements to [LSPPING], [BFD-MPLS] or the use of [TUNTRACE] to gain
   full end-to-end visibility. These protocols should, however, be
   considered in the light of confidentiality requirements.

   Route recording is a commonly used feature of signaling that provides
   OAM information about the path of an established LSP. When an LSP
   traverses a domain boundary, the border node may remove or aggregate
   some of the recorded information for confidentiality or other policy
   reasons.

5.9. Point-to-Multipoint

   Inter-domain point-to-multipoint (P2MP) requirements are explicitly
   out of scope of this document. They may be covered by other documents
   dependent on the details of MPLS TE P2MP solutions.

5.10. Applicability to Non-Packet Technologies

   Non-packet switching technologies may present particular issues for
   inter-domain LSPs. While packet switching networks may utilize
   control planes built on MPLS or GMPLS technology, non-packet networks
   are limited to GMPLS.

   The specific architectural considerations and requirements for
   inter-domain LSP setup in non-packet networks are covered in a
   separate document [GMPLS-AS].





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6. Security Considerations

   Requirements for security within domains are unchanged from [RFC3209]
   and [RFC3473], but requirements for inter-domain security are, if
   anything, more significant.

   Authentication techniques identified for use with RSVP-TE can only
   operate across domain boundaries if there is coordination between the
   administrators of those domains.

   Confidentiality may also be considered to be security factors.

   Applicability statements for particular combinations of signaling,
   routing and path computation techniques are expected to contain
   detailed security sections.

7. IANA Considerations

   This document makes no requests for any IANA action.

8. Acknowledgements

   The authors would like to extend their warmest thanks to Kireeti
   Kompella for convincing them to expend effort on this document.

   Grateful thanks to Dimitri Papadimitriou and Tomohiro Otani for their
   review and suggestions on the text.

9. Intellectual Property Considerations

   The IETF takes no position regarding the validity or scope of any
   Intellectual Property Rights or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; nor does it represent that it has
   made any independent effort to identify any such rights. Information
   on the procedures with respect to rights in RFC documents can be
   found in BCP 78 and BCP 79.

   Copies of IPR disclosures made to the IETF Secretariat and any
   assurances of licenses to be made available, or the result of an
   attempt made to obtain a general license or permission for the use of
   such proprietary rights by implementers or users of this
   specification can be obtained from the IETF on-line IPR repository at
   http://www.ietf.org/ipr.






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draft-ietf-ccamp-inter-domain-framework-01.txt             February 2005

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights that may cover technology that may be required to implement
   this standard. Please address the information to the IETF at
   ietf-ipr@ietf.org.


10. Normative References

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

   [RFC3209]     Awduche, et al, "Extensions to RSVP for LSP Tunnels",
                 RFC 3209, December 2001.

   [RFC3473]     Berger, L., Editor "Generalized Multi-Protocol Label
                 Switching (GMPLS) Signaling - Resource ReserVation
                 Protocol-Traffic Engineering (RSVP-TE) Extensions",
                 RFC 3473, January 2003.

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

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

   [HIER]        Kompella K., Rekhter Y., "LSP Hierarchy with
                 Generalized MPLS TE", draft-ietf-mpls-lsp-hierarchy,
                 work in progress.

   [INTER-AREA]  Le Roux, Vasseur et Boyle, "Requirements for support of
                 Inter-Area and Inter-AS MPLS Traffic Engineering",
                 draft-ietf-tewg-interarea-mpls-te-req, work in
                 progress.

   [INTER-AS]    Zhang, R., Vasseur, JP. et al, "MPLS Inter-AS Traffic
                 Engineering requirements",
                 draft-ietf-tewg-interas-mpls-te-req, work in progress.

   [STITCH]      Ayyangar, A., and Vasseur, JP., "LSP Stitching with
                 Generalized MPLS TE",
                 draft-ayyangar-ccamp-lsp-stitching, work in progress.

   [PCE]         Ash, G., Farrel, A., and Vasseur, JP., "Path
                 Computation Element (PCE) Architecture",
                 draft-ash-pce-architecture, work in progress.





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draft-ietf-ccamp-inter-domain-framework-01.txt             February 2005

11. Informational References

   [RFC3630]     Katz, D., Yeung, D., Kompella, K., "Traffic Engineering
                 Extensions to OSPF Version 2", RFC 3630, September 2003

   [RFC3784]     Li, T., Smit, H., "IS-IS extensions for Traffic
                 Engineering", RFC 3784, June 2004.
   [ATTRIB]      A. Farrel, D. Papadimitriou, JP. Vasseur, "Encoding of
                 Attributes for Multiprotocol Label Switching (MPLS)
                 Label Switched Path (LSP) Establishment Using RSVP-TE",
                 draft-ietf-mpls-rsvpte-attributes, work in progress.

   [BFD-MPLS]    R. Aggarwal and K. Kompella, "BFD For MPLS LSPs", work
                 in progress.

   [CRANKBACK]   Farrel, A., et al., "Crankback Signaling Extensions for
                 MPLS Signaling", draft-ietf-ccamp-crankback,
                 work in progress.

   [EXCLUDE]     Lee et all, Exclude Routes - Extension to RSVP-TE,
                 draft-ietf-ccamp-rsvp-te-exclude-route, work in
                 progress.

   [FRR]         Ping Pan, et al, "Fast Reroute Extensions to RSVP-TE
                 for LSP Tunnels", draft-ietf-mpls-rsvp-lsp-fastreroute,
                 work in progress.

   [GMPLS-AS]    Otani, T., Kumaki, K., and Okamoto, S., "GMPLS Inter-AS
                 Traffic Engineering Requirements",
                 draft-otani-ccamp-interas-GMPLS-TE, work in progress.

   [LSPPING]     Kompella, K., et al., " Detecting Data Plane Liveliness
                 in MPLS", draft-ietf-mpls-lsp-ping, work in progress.

   [MRN]         K. Shiomoto, et al., "Requirements for GMPLS-based
                 multi-region and multi-layer networks",
                 draft-shiomoto-ccamp-gmpls-mrn-reqs, work in progress.

   [OVERLAY]     G. Swallow et al, "GMPLS RSVP Support for the Overlay
                 Model", draft-ietf-ccamp-gmpls-overlay, work in
                 progress.

   [SEG-PROT]    Berger, L., Bryskin, I., Papadimitriou, D. and Farrel,
                 A., "GMPLS Based Segment Recovery",
                 draft-ietf-ccamp-gmpls-segment-recovery, work in
                 progress.

   [TUNTRACE]    Bonica, R., et al., "Generic Tunnel Tracing Protocol
                 (GTTP) Specification", draft-ietf-ccamp-tunproto,
                 work in progress.

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12. Authors' Addresses

   Adrian Farrel
   Old Dog Consulting
   EMail:  adrian@olddog.co.uk

   Jean-Philippe Vasseur
   Cisco Systems, Inc.
   300 Beaver Brook Road
   Boxborough , MA - 01719
   USA
   Email: jpv@cisco.com

   Arthi Ayyangar
   Juniper Networks, Inc
   1194 N.Mathilda Ave
   Sunnyvale, CA 94089
   USA
   Email: arthi@juniper.net

13. Full Copyright Statement

   Copyright (C) The Internet Society (2005). 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 AND THE INTERNET
   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.


















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