Subject: IPv6 Traffic class field or DS field ??

From: "Nikki Cranley" <[email-masked]>
Date: Wed, 23 Aug 2000 13:09:42 +0100

Hi 
sorry if this old hat for you! and a really stupid question but could anyone help? 

I have been reading the RFC's relating to IPv6 for some insight to the replacement for the ipv4 TOS field. In rfc 2460, there is talk about a traffic class field and then in rfc 2474 it talks about a differentiated services field. Could anyone tell me which has been "accepted" and if so where I could find out more details about this particular field and the various priorities etc.  as I am interested in trying to use this field for some qos mechanisms.

Thanking you, rgds,
Nik

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From: John Stracke <[email-masked]>
Date: Thu, 24 Aug 2000 10:37:44 -0400

Nikki Cranley wrote:

> I have been reading the RFC's relating to IPv6 for some insight
> to the replacement for the ipv4 TOS field.

It would not be surprising if there were no replacement; TOS
turns out to be problematic.  It's the usual problem with
unauthenticated priority fields: the network element processing a
packet has no particular reason to believe the sender's
assessment of the  packet's priority.

--
/==============================================================\
|John Stracke    | http://www.ecal.com |My opinions are my own.|
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[email-masked]|                                             |
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From: Fred Baker <[email-masked]>
Date: Thu, 24 Aug 2000 09:10:45 -0700

At 01:09 PM 8/23/00 +0100, Nikki Cranley wrote:
>I have been reading the RFC's relating to IPv6 for some insight to the 
>replacement for the ipv4 TOS field. In rfc 2460, there is talk about a 
>traffic class field and then in rfc 2474 it talks about a differentiated 
>services field. Could anyone tell me which has been "accepted" and if so 
>where I could find out more details about this particular field and the 
>various priorities etc.  as I am interested in trying to use this field 
>for some qos mechanisms.

The IPv6 traffic class field is discussed in RFCs 2460, 2473, 2474, 2553, 
and internet drafts draft-iab-case-for-ipv6-06.txt and 
draft-ietf-ipngwg-rfc2553bis-00.txt .  Section 7 of RFC 2460 makes it clear 
that the intended content of the traffic class field is identifical with 
the 8 bits containing the TOS byte and the "CU" field described in the 
Differentiated Services context.

In addition, RFC 2473 goes on to define the DS Field, making these two 
equivalent.

    Differentiated Services Field: the IPv4 header TOS octet or the IPv6
    Traffic Class octet when interpreted in conformance with the
    definition given in this document.  Also DS field.

You may find information about Differentiated Services and the DS Field in

2474 Definition of the Differentiated Services Field (DS Field) in the
      IPv4 and IPv6 Headers. K. Nichols, S. Blake, F. Baker, D. Black.
      December 1998. (Format: TXT=50576 bytes) (Obsoletes RFC1455, RFC1349)
      (Status: PROPOSED STANDARD)

2475 An Architecture for Differentiated Service. S. Blake, D. Black,
      M. Carlson, E. Davies, Z. Wang, W. Weiss. December 1998. (Format:
      TXT=94786 bytes) (Status: INFORMATIONAL)

2597 Assured Forwarding PHB Group. J. Heinanen, F. Baker, W. Weiss, J.
      Wroclawski. June 1999. (Format: TXT=24068 bytes) (Status: PROPOSED
      STANDARD)

2598 An Expedited Forwarding PHB. V. Jacobson, K. Nichols, K. Poduri.
      June 1999. (Format: TXT=23656 bytes) (Status: PROPOSED STANDARD)

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From: Lloyd Wood <[email-masked]>
Date: Thu, 24 Aug 2000 18:25:50 +0100 (BST)

> > to the replacement for the ipv4 TOS field.

Read the differentiated services RFCs. diffserv is intended to work
across v4 and v6.

> assessment of the  packet's priority.

diffserv domains and service-level specifications should address that
somewhat.

L.

<[email-masked]>PGP<http://www.ee.surrey.ac.uk/Personal/L.Wood/>