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GMPLS Asymmetric Bandwidth Bidirectional Label Switched Paths (LSPs) :: RFC5467








Network Working Group                                          L. Berger
Request for Comments: 5467                                          LabN
Category: Experimental                                         A. Takacs
                                                                Ericsson
                                                             D. Caviglia
                                                                Ericsson
                                                                D. Fedyk
                                                                  Nortel
                                                               J. Meuric
                                                          France Telecom
                                                              March 2009


  GMPLS Asymmetric Bandwidth Bidirectional Label Switched Paths (LSPs)

Status of This Memo

   This memo defines an Experimental Protocol for the Internet
   community.  It does not specify an Internet standard of any kind.
   Discussion and suggestions for improvement are requested.
   Distribution of this memo is unlimited.

Copyright Notice

   Copyright (c) 2009 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   Please review these documents carefully, as they describe your rights
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   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
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   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.







Berger, et al.                Experimental                      [Page 1]

RFC 5467         Asymmetric Bandwidth Bidirectional LSP       March 2009


Abstract

   This document defines a method for the support of GMPLS asymmetric
   bandwidth bidirectional Label Switched Paths (LSPs).  The presented
   approach is applicable to any switching technology and builds on the
   original Resource Reservation Protocol (RSVP) model for the transport
   of traffic-related parameters.  The procedures described in this
   document are experimental.

Table of Contents

   1. Introduction ....................................................2
      1.1. Background .................................................3
      1.2. Approach Overview ..........................................3
      1.3. Conventions Used in This Document ..........................4
   2. Generalized Asymmetric Bandwidth Bidirectional LSPs .............4
      2.1. UPSTREAM_FLOWSPEC Object ...................................5
           2.1.1. Procedures ..........................................5
      2.2. UPSTREAM_TSPEC Object ......................................5
           2.2.1. Procedures ..........................................5
      2.3. UPSTREAM_ADSPEC Object .....................................6
           2.3.1. Procedures ..........................................6
   3. Packet Formats ..................................................6
   4. Compatibility ...................................................7
   5. IANA Considerations .............................................8
      5.1. UPSTREAM_FLOWSPEC Object ...................................8
      5.2. UPSTREAM_TSPEC Object ......................................8
      5.3. UPSTREAM_ADSPEC Object .....................................8
   6. Security Considerations .........................................8
   7. References ......................................................9
      7.1. Normative References .......................................9
      7.2. Informative References .....................................9
   Appendix A. Alternate Approach Using ADSPEC Object.................11
      A.1. Applicability .............................................11
      A.2. Overview ..................................................11
      A.3. Procedures ................................................12
      A.4. Compatibility .............................................13

1.  Introduction

   GMPLS [RFC3473] introduced explicit support for bidirectional Label
   Switched Paths (LSPs).  The defined support matched the switching
   technologies covered by GMPLS, notably Time Division Multiplexing
   (TDM) and lambdas; specifically, it only supported bidirectional LSPs
   with symmetric bandwidth allocation.  Symmetric bandwidth
   requirements are conveyed using the semantics objects defined in
   [RFC2205] and [RFC2210].




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RFC 5467         Asymmetric Bandwidth Bidirectional LSP       March 2009


   Recent work ([GMPLS-PBBTE] and [MEF-TRAFFIC]) has looked at extending
   GMPLS to control Ethernet switching.  In this context, there has been
   discussion of the support of bidirectional LSPs with asymmetric
   bandwidth.  (That is, bidirectional LSPs that have different
   bandwidth reservations in each direction.)  This discussion motivated
   the extensions defined in this document, which may be used with any
   switching technology to signal asymmetric bandwidth bidirectional
   LSPs.  The procedures described in this document are experimental.

1.1.  Background

   Bandwidth parameters are transported within RSVP ([RFC2210],
   [RFC3209], and [RFC3473]) via several objects that are opaque to
   RSVP.  While opaque to RSVP, these objects support a particular model
   for the communication of bandwidth information between an RSVP
   session sender (ingress) and receiver (egress).  The original model
   of communication, defined in [RFC2205] and maintained in [RFC3209],
   used the SENDER_TSPEC and ADSPEC objects in Path messages and the
   FLOWSPEC object in Resv messages.  The SENDER_TSPEC object was used
   to indicate a sender's data generation capabilities.  The FLOWSPEC
   object was issued by the receiver and indicated the resources that
   should be allocated to the associated data traffic.  The ADSPEC
   object was used to inform the receiver and intermediate hops of the
   actual resources allocated for the associated data traffic.

   With the introduction of bidirectional LSPs in [RFC3473], the model
   of communication of bandwidth parameters was implicitly changed.  In
   the context of [RFC3473] bidirectional LSPs, the SENDER_TSPEC object
   indicates the desired resources for both upstream and downstream
   directions.  The FLOWSPEC object is simply confirmation of the
   allocated resources.  The definition of the ADSPEC object is either
   unmodified and only has meaning for downstream traffic, or is
   implicitly or explicitly ([RFC4606] and [MEF-TRAFFIC]) irrelevant.

1.2.  Approach Overview

   The approach for supporting asymmetric bandwidth bidirectional LSPs
   defined in this document builds on the original RSVP model for the
   transport of traffic-related parameters and GMPLS's support for
   bidirectional LSPs.  An alternative approach was considered and
   rejected in favor of the more generic approach presented below.  For
   reference purposes only, the rejected approach is summarized in
   Appendix A.

   The defined approach is generic and can be applied to any switching
   technology supported by GMPLS.  With this approach, the existing
   SENDER_TSPEC, ADSPEC, and FLOWSPEC objects are complemented with the
   addition of new UPSTREAM_TSPEC, UPSTREAM_ADSPEC, and



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RFC 5467         Asymmetric Bandwidth Bidirectional LSP       March 2009


   UPSTREAM_FLOWSPEC objects.  The existing objects are used in the
   original fashion defined in [RFC2205] and [RFC2210], and refer only
   to traffic associated with the LSP flowing in the downstream
   direction.  The new objects are used in exactly the same fashion as
   the old objects, but refer to the upstream traffic flow.  Figure 1
   shows the bandwidth-related objects used for asymmetric bandwidth
   bidirectional LSPs.

                        |---|        Path        |---|
                        | I |------------------->| E |
                        | n | -SENDER_TSPEC      | g |
                        | g | -ADSPEC            | r |
                        | r | -UPSTREAM_FLOWSPEC | e |
                        | e |                    | s |
                        | s |        Resv        | s |
                        | s |<-------------------|   |
                        |   | -FLOWSPEC          |   |
                        |   | -UPSTREAM_TSPEC    |   |
                        |   | -UPSTREAM_ADSPEC   |   |
                        |---|                    |---|

         Figure 1: Generic Asymmetric Bandwidth Bidirectional LSPs

   The extensions defined in this document are limited to Point-to-Point
   (P2P) LSPs.  Support for Point-to-Multipoint (P2MP) bidirectional
   LSPs is not currently defined and, as such, not covered in this
   document.

1.3.  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 [RFC2119].

2.  Generalized Asymmetric Bandwidth Bidirectional LSPs

   The setup of an asymmetric bandwidth bidirectional LSP is signaled
   using the bidirectional procedures defined in [RFC3473] together with
   the inclusion of the new UPSTREAM_FLOWSPEC, UPSTREAM_TSPEC, and
   UPSTREAM_ADSPEC objects.

   The new upstream objects carry the same information and are used in
   the same fashion as the existing downstream objects; they differ in
   that they relate to traffic flowing in the upstream direction while
   the existing objects relate to traffic flowing in the downstream
   direction.  The new objects also differ in that they are used on
   messages in the opposite directions.




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RFC 5467         Asymmetric Bandwidth Bidirectional LSP       March 2009


2.1.  UPSTREAM_FLOWSPEC Object

   The format of an UPSTREAM_FLOWSPEC object is the same as a FLOWSPEC
   object.  This includes the definition of class types and their
   formats.  The class number of the UPSTREAM_FLOWSPEC object is 120 (of
   the form 0bbbbbbb).

2.1.1.  Procedures

   The Path message of an asymmetric bandwidth bidirectional LSP MUST
   contain an UPSTREAM_FLOWSPEC object and MUST use the bidirectional
   LSP formats and procedures defined in [RFC3473].  The C-Type of the
   UPSTREAM_FLOWSPEC object MUST match the C-Type of the SENDER_TSPEC
   object used in the Path message.  The contents of the
   UPSTREAM_FLOWSPEC object MUST be constructed using a format and
   procedures consistent with those used to construct the FLOWSPEC
   object that will be used for the LSP, e.g., [RFC2210] or [RFC4328].

   Nodes processing a Path message containing an UPSTREAM_FLOWSPEC
   object MUST use the contents of the UPSTREAM_FLOWSPEC object in the
   upstream label and the resource allocation procedure defined in
   Section 3.1 of [RFC3473].  Consistent with [RFC3473], a node that is
   unable to allocate a label or internal resources based on the
   contents of the UPSTREAM_FLOWSPEC object MUST issue a PathErr message
   with a "Routing problem/MPLS label allocation failure" indication.

2.2.  UPSTREAM_TSPEC Object

   The format of an UPSTREAM_TSPEC object is the same as a SENDER_TSPEC
   object.  This includes the definition of class types and their
   formats.  The class number of the UPSTREAM_TSPEC object is 121 (of
   the form 0bbbbbbb).

2.2.1.  Procedures

   The UPSTREAM_TSPEC object describes the traffic flow that originates
   at the egress.  The UPSTREAM_TSPEC object MUST be included in any
   Resv message that corresponds to a Path message containing an
   UPSTREAM_FLOWSPEC object.  The C-Type of the UPSTREAM_TSPEC object
   MUST match the C-Type of the corresponding UPSTREAM_FLOWSPEC object.
   The contents of the UPSTREAM_TSPEC object MUST be constructed using a
   format and procedures consistent with those used to construct the
   FLOWSPEC object that will be used for the LSP, e.g., [RFC2210] or
   [RFC4328].  The contents of the UPSTREAM_TSPEC object MAY differ from
   contents of the UPSTREAM_FLOWSPEC object based on application data
   transmission requirements.





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   When an UPSTREAM_TSPEC object is received by an ingress, the ingress
   MAY determine that the original reservation is insufficient to
   satisfy the traffic flow.  In this case, the ingress MAY issue a Path
   message with an updated UPSTREAM_FLOWSPEC object to modify the
   resources requested for the upstream traffic flow.  This modification
   might require the LSP to be re-routed, and in extreme cases might
   result in the LSP being torn down when sufficient resources are not
   available.

2.3.  UPSTREAM_ADSPEC Object

   The format of an UPSTREAM_ADSPEC object is the same as an ADSPEC
   object.  This includes the definition of class types and their
   formats.  The class number of the UPSTREAM_ADSPEC object is 122 (of
   the form 0bbbbbbb).

2.3.1.  Procedures

   The UPSTREAM_ADSPEC object MAY be included in any Resv message that
   corresponds to a Path message containing an UPSTREAM_FLOWSPEC object.
   The C-Type of the UPSTREAM_TSPEC object MUST be consistent with the
   C-Type of the corresponding UPSTREAM_FLOWSPEC object.  The contents
   of the UPSTREAM_ADSPEC object MUST be constructed using a format and
   procedures consistent with those used to construct the ADSPEC object
   that will be used for the LSP, e.g., [RFC2210] or [MEF-TRAFFIC].  The
   UPSTREAM_ADSPEC object is processed using the same procedures as the
   ADSPEC object and, as such, MAY be updated or added at transit nodes.

3.  Packet Formats

   This section presents the RSVP message-related formats as modified by
   this section.  This document modifies formats defined in [RFC2205],
   [RFC3209], and [RFC3473].  See [RSVP-BNF] for the syntax used by
   RSVP.  Unmodified formats are not listed.  Three new objects are
   defined in this section:

      Object name            Applicable RSVP messages
      ---------------        ------------------------
      UPSTREAM_FLOWSPEC      Path, PathTear, PathErr, and Notify
                                 (via sender descriptor)
      UPSTREAM_TSPEC         Resv, ResvConf, ResvTear, ResvErr, and
                                 Notify (via flow descriptor list)
      UPSTREAM_ADSPEC        Resv, ResvConf, ResvTear, ResvErr, and
                                 Notify (via flow descriptor list)







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   The format of the sender description for bidirectional asymmetric
   LSPs is:

       ::=   
                               [  ]
                               [  ]
                               [  ]
                               [  ]
                               
                               

   The format of the flow descriptor list for bidirectional asymmetric
   LSPs is:

       ::= 
                               | 

       ::= 
                                [  ]
                               
                               

 

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