draft-ietf-mpls-cosfield-def-03.txt   draft-ietf-mpls-cosfield-def-04.txt 
Network Working Group L. Andersson Network Working Group L. Andersson
Internet-Draft Acreo AB Internet-Draft Acreo AB
Updates: RFC 3032, RFC 3270, RFC July 4, 2008 Updates: RFC 3032, RFC 3270, RFC July 7, 2008
5129, RFC 3272, RFC 3443, RFC 5129, RFC 3272, RFC 3443, RFC
3469, RFC 3564, RFC 3985, RFC 3469, RFC 3564, RFC 3985, RFC
4182, RFC 4364, RFC 4379, RFC 4182, RFC 4364, RFC 4379, RFC
4448, RFC 4761 (if approved) 4448, RFC 4761 (if approved)
Intended status: Standards Track Intended status: Standards Track
Expires: January 5, 2009 Expires: January 8, 2009
"EXP field" renamed to "CoS Field" "EXP field" renamed to "CoS Field"
draft-ietf-mpls-cosfield-def-03.txt draft-ietf-mpls-cosfield-def-04.txt
Status of this Memo Status of this Memo
By submitting this Internet-Draft, each author represents that any By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes have been or will be disclosed, and any of which he or she becomes
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
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This Internet-Draft will expire on January 5, 2009. This Internet-Draft will expire on January 8, 2009.
Abstract Abstract
The early MPLS documents defined the form of the MPLS Label Stack The early MPLS documents defined the form of the MPLS Label Stack
entry. This include a three bit field called the "EXP field". The entry. This include a three bit field called the "EXP field". The
exact use of this field was not defined by these documents, except to exact use of this field was not defined by these documents, except to
state that it was to be "reserved for experimental use". state that it was to be "reserved for experimental use".
Although the intended use of the EXP field was as a "Class of Although the intended use of the EXP field was as a "Class of
Service" field, it was not named the "Class of Service" (CoS) field Service" field, it was not named the "Class of Service" (CoS) field
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exact use of this field is not defined by RFC 3032 leaves, except to exact use of this field is not defined by RFC 3032 leaves, except to
state that it is to be "reserved for experimental use". state that it is to be "reserved for experimental use".
The EXP field, from the start, was intended to carry "Class of The EXP field, from the start, was intended to carry "Class of
Service" information. The field was actually called the "Class of Service" information. The field was actually called the "Class of
Service field" in the early versions of the working group document Service field" in the early versions of the working group document
that was publshed as RFC 3032. However at the time that RFC 3032 was that was publshed as RFC 3032. However at the time that RFC 3032 was
published the exact usage of this "Class of Service" field was not published the exact usage of this "Class of Service" field was not
agreed and the field was designated as "Experimental use". agreed and the field was designated as "Experimental use".
The designation "for Experimental use" has lead other Standards The designation "for Experimental use" has led other Standards
Development Organizations (SDO) and implementors to the assume that Development Organizations (SDO) and implementors to the assume that
it possible to use the field for other purposes than Class of it possible to use the field for other purposes than Class of
Service. This document changes the name of the field to clearly Service. This document changes the name of the field to clearly
indicate its use. 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) were specified. Inferred-PSC LSP (E-LSPs) were specified.
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
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3. Class of Service (CoS) field 3. Class of Service (CoS) field
This three-bit field is used to carry Class of Service information This three-bit field is used to carry Class of Service information
and the change of the name is applicable to all places it occurs and the change of the name is applicable to all places it occurs
in IETF RFCs and other IETF documents. in IETF RFCs and other IETF documents.
The definition of how to use the CoS field has been updated by RFC The definition of how to use the CoS field has been updated by RFC
3270 and RFC 5129. 3270 and RFC 5129.
In Figure 1 on page 3 in RFC3032 the format of label stack entries is In Figure 1 on page 3 in RFC3032 the format of a label stack entry is
specified as: specified as:
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Label +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Label
| Label | Exp |S| TTL | Stack | Label | Exp |S| TTL | Stack
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Entry +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Entry
Label: Label Value, 20 bits Label: Label Value, 20 bits
Exp: Experimental Use, 3 bits Exp: Experimental Use, 3 bits
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[RFC3443], RFC 3469 [RFC3469], RFC 3564 [RFC3564], RFC 3985 [RFC3443], RFC 3469 [RFC3469], RFC 3564 [RFC3564], RFC 3985
[RFC3985], RFC 4182 [RFC4182], RFC 4364 [RFC4364], RFC 4379 [RFC3985], RFC 4182 [RFC4182], RFC 4364 [RFC4364], RFC 4379
[RFC4379], RFC 4448 [RFC4448] and RFC 4761 [RFC4761] that references [RFC4379], RFC 4448 [RFC4448] and RFC 4761 [RFC4761] that references
the "Exp field", sometimes they refer to the field as "Exp bits", the "Exp field", sometimes they refer to the field as "Exp bits",
"EXP bits" and "EXP". For all RFCs, including but not limited to "EXP bits" and "EXP". For all RFCs, including but not limited to
those mentioned in this paragraph, such references SHOULD be taken to those mentioned in this paragraph, such references SHOULD be taken to
reference the CoS field. reference the CoS field.
3. Use of the CoS field 3. Use of the CoS field
Due to the limited number of bits the particular use of the bits is Due to the limited number of bits in the CoS field, their use for QoS
intended to be flexible - including the definition of various QoS and and ECN functions is intended to be flexible. These funtions may
ECN functions. rewrite all or some of the bits in the CoS field.
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 label stack entries context and the CoS field may be copied to the label stack entries
that are pushed onto the label stack. This is to avoid the pushed that are pushed onto the label stack. This is to avoid the pushed
label stack entries having a different CoS field. label stack entries having a different CoS field.
CoS and ECN funtions may rewrite all or some of the bits.
4. IANA considerations 4. IANA considerations
There are no request for IANA allocation of code points in this There are no request for IANA allocation of code points in this
document. 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 does not introduce any new security considerations. Header and thus does not introduce any new security considerations.
6. Acknowledgments 6. Acknowledgments
The author would like to thank Stewart Bryant, Bruce Davie, George The author would like to thank Stewart Bryant, Bruce Davie, George
Swallow, and Francois Le Faucheur for their input to and review of Swallow, Rajiv Asatiand Francois Le Faucheur for their input to and
the current document. review of the current document.
The author also like to thanks George Swallow, Khatri Paresh and Phil The author also like to thanks George Swallow, Khatri Paresh and Phil
Bedard for their help with grammar and spelling, and a special thanks Bedard for their help with grammar and spelling, and a special thanks
to Adrian Farrel for a careful review and help trawling the RFC-sea to Adrian Farrel for a careful review and help trawling the RFC-sea
for RFCs that references the EXP field. for RFCs that references the EXP field.
7. References 7. References
7.1. Normative References 7.1. Normative References
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