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SFC Working Group                                   G. Van de Velde, Ed.
Internet-Draft                                              M. Vigoureux
Intended status: Standards Track                                P. Mulay
Expires: April 20, 2017                                            Nokia
                                                        October 17, 2016


         Network Services Header Context Allocation Identifier
              draft-vandevelde-sfc-nsh-length-overload-00

Abstract

   The specification of the NSH MD Type 1 header [draft-ietf-sfc-nsh]
   mandates four Context Headers, 4-byte each, and they MUST be added
   immediately following the Service Path Header.  As direct
   consequence, an NSH MD Type 1 header is always Length 0x6 (six 4-byte
   words).  As a result, the Length field of the NSH MD Type 1 header
   provides an information which is known by simply looking at the "MD
   Type" field.  However, while [draft-ietf-sfc-nsh] does not specify
   the encoding of these Context Headers, other specifications have
   started to do so.  A need to distinguish types of Context Headers
   therefore arises.

   This draft proposes to overload the Length field of an NSH MD Type 1
   as Meta-Data context allocation identifier and to create a IANA
   repository for NSH MD Type 1 allocation schemes.  The NSH MD Type 1
   Length field overload intends to allow universal understanding at any
   network location and by any network device of the context allocation
   structure.

Requirements Language

   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 [1].

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any



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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on April 20, 2017.

Copyright Notice

   Copyright (c) 2016 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
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Operation . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   4.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   4
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   4

1.  Introduction

   The specification of the NSH MD Type 1 header [draft-ietf-sfc-nsh]
   mandates four Context Headers, 4-byte each, and they MUST be added
   immediately following the Service Path Header.  As direct
   consequence, an NSH MD Type 1 header is always Length 0x6 (six 4-byte
   words).  As a result, the Length field of the NSH MD Type 1 header
   provides an information which is known by simply looking at the "MD
   Type" field.  However, while [draft-ietf-sfc-nsh] does not specify
   the encoding of these Context Headers, other specifications have
   started to do so.  A need to distinguish types of Context Headers
   therefore arises.

   This draft proposes to overload the Length field of an NSH MD Type 1
   as Meta-Data context allocation identifier and to create a IANA
   repository for NSH MD Type 1 allocation schemes.  The NSH MD Type 1



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   Length field overload intends to allow universal understanding at any
   network location and by any network device of the context allocation
   structure.

   The capability of overloading the NSH MD Type 1 Length field as
   context allocation identifier is particular useful in networks
   environments where multiple different NSH MD Type 1 allocation
   schemes exist simultaneously.  For example in Datacenters where data-
   flows are serviced and allocations are based upon either [draft-
   guichard-sfc-nsh-dc-allocation] or [draft-napper-sfc-nsh-broadband-
   allocation].  Without Length field overload, it is for a servicing
   node non-trivial to know how the NSH Meta Data is structured and how
   the Meta Data should be consumed without provisioning of additional
   context information to understand the NSH embedded Meta-Data.

   In addition, this document serves as anchor-point to request an IANA
   repository for NSH MD Type 1 allocation schemes.

2.  Operation

   The Length field in the NSH Base header intends to provide the length
   of the NSH header including the Base header itself in 4-byte words.
   According [draft-ietf-sfc-nsh] the NSH MD Type 1 the value within the
   Length field MUST always be 0x6.

   This note proposes a different usage for the length field taking
   backward compatibility into account.  This draft proposes to use the
   Length field of a fixed length NSH MD Type 1 header as indication of
   the Meta Data allocation scheme.  The allocation scheme context
   overloading of the length field does not modify the fixed length of
   the NSH MD Type 1 fields and expected Meta Data fields is fixed at
   four words of 4-byte data.

   The different from 0x6 value represents the Meta Data allocation
   scheme used for the NSH MD Type 1 header.  To avoid compatibility
   issues with older NSH MD Type implementations the Length value of 0x6
   is reserved and allows existing NSH MD Type 1 usage to carry opaque
   Meta Data.

   The following MD allocation types have been defined:

   0x0: draft-guichard-sfc-nsh-dc-allocation

   0x1: draft-napper-sfc-nsh-broadband-allocation

   0x6: draft-ietf-sfc-nsh





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3.  Security Considerations

   tbc

4.  Acknowledgements

   tbc

5.  IANA Considerations

   This document requests IANA to setup a central repository to keep
   track of the different NSH MD Type 1 allocation schemes

6.  References

6.1.  Normative References

   [1]        Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

6.2.  Informative References

   [2]        Halpern, J., Ed. and C. Pignataro, Ed., "Service Function
              Chaining (SFC) Architecture", RFC 7665,
              DOI 10.17487/RFC7665, October 2015,
              <http://www.rfc-editor.org/info/rfc7665>.

Authors' Addresses

   Gunter Van de Velde (editor)
   Nokia
   Antwerp
   Belgium

   Email: gunter.van_de_velde@nokia.com


   Martin Vigoureux
   Nokia
   Route de Villejust
   Nozay 91620
   France

   Email: martin.vigoureux@nokia.com





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   Praveen Mulay
   Nokia
   Mountain View
   USA

   Email: praveen.muley@nokia.com













































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