draft-ietf-mpls-cosfield-def-00.txt   draft-ietf-mpls-cosfield-def-01.txt 
Network Working Group L. Andersson Network Working Group L. Andersson
Internet-Draft Acreo AB Internet-Draft Acreo AB
Intended status: Standards Track May 19, 2008 Intended status: Standards Track June 4, 2008
Expires: November 20, 2008 Expires: December 6, 2008
"EXP field" renamed to "CoS Field" "EXP field" renamed to "CoS Field"
draft-ietf-mpls-cosfield-def-00.txt draft-ietf-mpls-cosfield-def-01.txt
Status of this Memo Status of this Memo
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Abstract Abstract
- The early MPLS documents defined the MPLS format, this definition
includes three bit field called "EXP field". The documentats leaves
the exact description of how the EXP field should be used undefined,
it is said said to be for "experimental use".
The EXP field has from the start been intended to be used for "Class
of Service". At the time the documents were published the use of
such a CoS field were considered not to be defined well enough and
the field were left for "Experimental use".
To avoid misunderstanding about how this field may be used this
document re-introduces the name "CoS field" for this field. In doing
so it also updates documents that defines and uses this field.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Details of change . . . . . . . . . . . . . . . . . . . . . . 4 2. Details of change . . . . . . . . . . . . . . . . . . . . . . 4
2.1. RFC 3032 . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1. RFC 3032 . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. RFC 3270 . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.2. RFC 3270 . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.3. RFC 5129 . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.3. RFC 5129 . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Use of the CoS field . . . . . . . . . . . . . . . . . . . . . 7 3. Use of the CoS field . . . . . . . . . . . . . . . . . . . . . 7
4. IANA considerations . . . . . . . . . . . . . . . . . . . . . 8 4. IANA considerations . . . . . . . . . . . . . . . . . . . . . 8
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6.1. Normative References . . . . . . . . . . . . . . . . . . . 10 6.1. Normative References . . . . . . . . . . . . . . . . . . . 10
6.2. Informative references . . . . . . . . . . . . . . . . . . 10 6.2. Informative references . . . . . . . . . . . . . . . . . . 10
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 11 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 11
Intellectual Property and Copyright Statements . . . . . . . . . . 12 Intellectual Property and Copyright Statements . . . . . . . . . . 12
1. Introduction 1. Introduction
The format of the MPLS label is defined in RFC 3032 [RFC3032], that The format of the MPLS label is defined in RFC 3032 [RFC3032], that
definition includes three bit field called "EXP field". RFC 3032 definition includes three bit field called "EXP field". RFC 3032
leaves the exact description of how the EXP field should be used leaves the exact description of how the EXP field should be used
undefined, they are said to be for "experimental use". undefined, it is said to be for "experimental use".
The EXP field has from the start been intended to be used for "Class The EXP field has from the start been intended to be used for "Class
of Service", the field were actually called "Class of Service field" of Service", the field were actually called "Class of Service field"
in the early versions of the working group document that was publshed in the early versions of the working group document that was publshed
as RFC 3032. However at the time that RFC 3032 were published the as RFC 3032. However at the time that RFC 3032 were published the
"Class of Service" were considered not to be defined well enough and "Class of Service" were considered not to be defined well enough and
the field were left for "Experimental use". the field were left for "Experimental use".
Since the "for Experimental use" terminology has lead other Standards
Development Organizations (SDO) and implementors to the assume that
it possible to use the field for other purposes that Class of Service
we now changes the name of the field to clearly indicate its use.
The use of the EXP field was first defined in RFC 3270 [RFC3270] The use of the EXP field was first defined in RFC 3270 [RFC3270]
where a method to define a variant of DiffServ LSPs called EXP- where a method to define a variant of DiffServ LSPs called EXP-
Inferred-PSC LSP (E-LSPs). Inferred-PSC LSP (E-LSPs).
The use of the EXP field as defined in RFC 3270 has been further The use of the EXP field as defined in RFC 3270 has been further
extended in RFC 5129 [RFC5129], where methods for explicit congestion extended in RFC 5129 [RFC5129], where methods for explicit congestion
marking in MPLS is defined. marking in MPLS is defined.
The defintions of how the EXP field are used are perfectly clear in The defintions of how the EXP field are used are perfectly clear in
RFC 3270 and RFC 5129. However it is never explicitly stated that RFC 3270 and RFC 5129. However it is never explicitly stated that
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Current implementations look at the CoS field with and without label Current implementations look at the CoS field with and without label
context and the CoS field may be copied to the labels that are pushed context and the CoS field may be copied to the labels that are pushed
onto the laabel stack. This is to avoid that the pushed labels has a onto the laabel stack. This is to avoid that the pushed labels has a
different CoS field. different CoS field.
CoS and ECN funtions may rewrite all or some of the bits. CoS and ECN funtions may rewrite all or some of the bits.
4. IANA considerations 4. IANA considerations
TBD There are no request for IANA allocation of code points in this
document.
5. Security considerations 5. Security considerations
This document only changes the name of one field in the MPLS Shim This document only changes the name of one field in the MPLS Shim
Header and thus do not introduce any new security considerations. Header and thus do not introduce any new security considerations.
6. References 6. References
6.1. Normative References 6.1. Normative References
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