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
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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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Internet-Draft NSH MD Type-1 Context Allocation Identifier October 2016
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
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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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