Network Working Group                                         H. Long
Internet Draft                           Huawei Technologies Co., Ltd.
Intended status: Standards Track                          May 16, 2011
Expires: November 2011



      
Multi-Segment Pseudowire Signaling with Availability Information
                 
draft-long-pwe3-ms-pw-availability-00.txt


Abstract

   This document describes a signaling mechanism for setting up a multi-
   segment pseudowire between different domains in case that at least
   one domain has the feature that bandwidth capacity is variable for
   different availability values. The signaling mechanism is an
   extension on the multi-segment pseudowire signaling [DYN-MS-PW].

Status of this Memo

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   This Internet-Draft will expire on November 16, 2011.

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   Copyright (c) 2011 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
   Provisions Relating to IETF Documents



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   (http://trustee.ietf.org/license-info) in effect on the date of
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Table of Contents


   1. Introduction ................................................ 2
   2. LDP Signaling ............................................... 3
   3. Security Considerations...................................... 3
   4. IANA Considerations ......................................... 3
   5. References .................................................. 4
      5.1. Normative References.................................... 4
      5.2. Informative References.................................. 4
   6. Acknowledgments ............................................. 4

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].

. Introduction

   [RFC5659] describes the architecture of multi-segment pseudowire. The
   LDP signaling mechanism for setting up multi-segement pseudowire is
   described by [DYN-MS-PW]. The mechanism introduces a pseudowire
   bandwidth TLV for PSN tunnel selection.

   In many scenarios, a network may contain some non-fixed-bandwidth
   links. For example, the radio links may change their interface rates
   due to rain, fog, etc. The DSL links may change their interface rates
   due to external interference. The pair of <availability, bandwidth>
   is often used to describe the bandwidth capacity of the links during
   network planning. In this case, A LSP across the links will include
   multiple bandwidth portions with different availability guarantee. As
   the result, only PW bandwidth requirement information is not enough
   for the multi-segment pseudowire setup.

   An optional PW availability TLV is introduced in this document for
   providing enough information for S-PE to selecting PSN tunnel.




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. LDP Signaling

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |1|0|    Availability TLV(TBD)   |         TLV  Length          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Availability                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 1 PW Availability TLV

   The optional availability TLV described by Figure 1 is 32-bit
   floating point number which is smaller than 1. This field describes
   the availability requirement for the multi-segment pseudowire which
   is inherited from the availability requirement of the emulated
   service.

   When an S/T-PE receives a PW availability TLV and a PW bandwidth TLV,
   it will search for an PSN tunnel which can satisfy the bandwidth
   requirement with the availability requirement. Once the PW next hop
   is selected, the S/T-PE MUST request the appropriate resources which
   can guarantee the required availability from the PSN.

   In the case where PSN resources towards the previous hop are not
   available the following procedure MUST be followed:

     -i. The PSN MAY allocate more QoS resources, e.g. Bandwidth with
   required availability guranttee, to the PSN tunnel.
     -ii. The S-PE MAY attempt to setup another PSN tunnel to
   accommodate the new PW QoS requirements.
      -iii. If the S-PE cannot get enough resources to setup the segment
   in the MS-PW a label release MUST be returned to the previous hop
   with a status message of "Bandwidth resources unavailable"

   In the latter case, the T-PE receiving the status message MUST also
   withdraw the corresponding PW label mapping for the opposite
   direction if it has already been successfully setup.

. Security Considerations

   This document does not introduce new security considerations.

. IANA Considerations

   TBD.



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. References

5.1. Normative References

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

   [RFC5659] Bocci, M., Bryant, S., "An Architecture for Multi-Segment
             Pseudowire Emulation Edge-to-Edge", RFC 5659, October 2009.

   [DYN-MS-PW] Martini, L., Bocci, M., Balus, F., "Dynamic Placement of
             Multi Segment Pseudo Wires", draft-ietf-pwe3-dynamic-ms-pw-
             13, October, 2010



5.2. Informative References

   [GMPLS-BA] Long, H. "GMPLS Signaling Extension for Bandwidth
             availability", draft-long-ccamp-gmpls-availability-00,
             March, 2011.

. Acknowledgments



Authors' Addresses

   Hao Long
   Huawei Technologies Co., Ltd.
   Bantian, Longgang District
   Shenzhen 518129, P.R.China

   Phone: +86-18615778750
   Email: longhao@huawei.com













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