One document matched: draft-ietf-pppext-l2tp-ds-00.txt

PPP Working Group                                          Pat R. Calhoun
INTERNET DRAFT                                                 Ken Peirce
Category: Internet Draft                                 3Com Corporation
Title: draft-ietf-pppext-l2tp-ds-00.txt
Date: February 1998



                         Layer Two Tunneling Protocol ''L2TP''
                          IP Differential Services Extension


Status of this Memo

   This  document  is  an  Internet-Draft.  Internet-Drafts  are  working
   documents  of  the  Internet Engineering Task Force (IETF), its areas,
   and its working groups.  Note that other groups  may  also  distribute
   working documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months.
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   munnari.oz.au.

Abstract

   The L2TP document [1] defines the base protocol  which  describes  the
   method  of  tunneling  PPP  [2]  data. The L2TP base protocol does not
   address any Differential Services extensions.

   Since the market is reluctant to outsource  dial  access  without  any
   Quality  of  Service  assurances, this draft addresses this problem by
   allowing  each  L2TP  Data  Session  to  be  assigned  an  appropriate
   differential services indicator.

Table of Contents

      1.0 Introduction
      1.1 Conventions
      2.0 Quality of Service/Diferential Services Negotiation
      2.1 Differential Sevices Indicator Exchange
      3.0 Contacts
      4.0 References



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1.0 Introduction

   The  L2TP  protocol  specification  does  not   discuss   Quality   of
   Service/Differential  Services  in  any  way. The current state of the
   market has shown that many  customers  are  reluctant  to  adopt  L2TP
   without any quality of service assurances.

   This document will  describe  how  two  L2TP  peers  can  negotiate  a
   differential services indicator for a dial-in user.

   The mechanism  defined  in  this  document  assumes  that  the  Tunnel
   Initiator  determines what the user's appropriate service level is and
   sends the value in either the  SCCRQ  or  OCRQ  messages.  The  Tunnel
   Terminator  can  respond to the message by stating what it believes is
   the user's appropriate service level.  The  values  of  the  indicator
   supplied by the Tunnel Terminator will supercede those provided by the
   Tunnel Initiator if  a  difference  is  found.   However,  the  Tunnel
   Terminator  MUST  NOT propose a higher differential service level than
   was proposed by the Tunnel Initiator.

   In the case where the Tunnel Terminator does not propose ANY indicator
   (which  is  infered by the absence of the QOS AVPs in either the SCCRP
   or OCRP) the Tunnel Initiator will assume no QOS is  assigned  to  the
   session.

   A tunnel peer which violates the negotiated differential service level
   is liable to have it's tunnel shutdown.


1.1 Conventions

   The following language conventions are used in the items  of  specifi-
   cation in this document:

         o  MUST, SHALL, or MANDATORY -- This item is an absolute
            requirement of the specification.

         o  SHOULD or RECOMMEND -- This item should generally be followed
            for all but exceptional circumstances.

         o  MAY or OPTIONAL -- This item is truly optional and may be
            followed or ignored according to the needs of the
            implementor.


2.0 Quality of Service/Diferential Services Negotiation

   This section will define the new  AVPs  which  are  required  for  the
   Quality  of  Service  extension  of  the L2TP protocol. The AVPs allow
   designation of a Quality of Service level for a specific data channel.


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2.1 Differential Sevices Indicator AVP

   The Differential Services indicator AVP is found in the IPv4 hear Type
   of  Service  octet. This is the second octet in the header. The actual
   bit interpretation of the IP Precedence and Type of Service bit fields
   is  left  to  the appropriate documentation[2][3][4]. This document is
   concerned with defining a uniform exchange mechanism for the indicator
   only.

   The Differential Services Indicator  AVP  MAY  be  present  in  SCCRQ,
   SCCRP,  OCRQ  and OCRP. This message is used to inform the tunnel peer
   that a set of differential service indicator value SHOULD be used  for
   all packets related to the data channel associated with the Tunnel and
   Call Identifiers in the L2TP header [1].

   The presence of this AVP in the  SCCRQ  or  OCRQ  indicates  that  the
   tunnel  initiator  wishes  to  use  a  specific  differential  service
   indicator value on all data packets. However, the value found  in  the
   SCCRP  or  OCRP  indicate  the  value  which  the Tunnel Terminator is
   willing to accept.  However, the Tunnel Terminator MUST NOT propose  a
   higher  differential  service  level  than  was proposed by the Tunnel
   Initiator.

   A tunnel peer which violates the negotiated indicator value is  liable
   to have it's tunnel shutdown.


       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|1|0|0|        Length         |              43               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                1              |  Diff Serv Indicator Value    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      This AVP MAY be present in the messages shown above. It is  encoded
      with a Vendor ID of 43 (3Com Corporation) with the attribute set to
      1, marked as optional, with the indicator value as data.  This  AVP
      SHOULD  NOT  be hidden and is optional. When present, the L2TP peer
      is indicating that differential services  are  to  be  used  on  IP
      packets within the session's data channel.


3.0 Contacts

   Pat R. Calhoun
   3Com Corporation
   1800 Central Ave.
   Mount Prospect, Il, 60056
   Pat_Calhoun@mw.3com.com


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   (847) 342-6898

   Ken Peirce
   3Com Corporation
   1800 Central Ave.
   Mount Prospect, Il, 60056
   Ken_Peirce@mw.3com.com
   (847) 342-6894

4.0 References

   [1] K. Hamzeh, T. Kolar, M. Littlewood, G. Singh Pall, J. Taarud,
       A. J. Valencia, W. Verthein, W.M. Townsley, B. Palter,
       A. Rubens "Layer Two Tunneling Protocol (L2TP)",
       Internet draft, October 1997

   [2] D. Clark, J. Wroclawski, "An Approach to Service Allocation in
       the Internet", draft-clark-diff-svc-alloc-00.txt, July 1997.

   [3] P. Ferguson, "Simple Differential Services: IP TOS and
       Precedence, Delay Indication, and Drop Preference,",
       draft-ferguson-delay-drop-00.txt, November 1997

   [4] J. Heinanen, "Use of the IPv4 TOS Octet to Support Differential
       Services", draft-heinanen-diff-tos-octet-01.txt, November 1997



























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