Subject: 2460bis and the Traffic Class field

From: Brian Haberman <[email-masked]>
Date: Thu, 25 Aug 2016 16:32:36 -0400

All,
     I came across a discrepancy that I think is worth discussing. After
the publication of RFC 2460, RFC 2474 was published and that document
renames the IPv4 TOS and IPv6 Traffic Class fields
(https://tools.ietf.org/html/rfc2474#section-3). RFC 2474 is then
updated by RFC 3260 to provide a clarification on the name of the DS Field.

     I know that 2474 did not formally update 2460, but it seems that
there was an attempt to rename the Traffic Class field to be consistent
with its use. Do people think that 2460bis should incorporate those
changes to be consistent with 2474/3260?

Regards,
Brian

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From: "Manfredi, Albert E" <[email-masked]>
Date: Thu, 25 Aug 2016 21:11:10 +0000

> -----Original Message-----
> From: ipv6 [mailto:[email-masked]] On Behalf Of Brian Haberman

> changes to be consistent with 2474/3260?

One of those long-standing ambiguities, IMO. Yes, definitely, the question of whether DSCP is real, or whether it's just meant to apply in certain cases and can otherwise be ignored, should be put to rest. Or am I the only one who wonders whether the older and the newer were meant to coexist?

On the other hand, would this break anything that exists out there?

Bert

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From: Brian E Carpenter <[email-masked]>
Date: Fri, 26 Aug 2016 11:03:57 +1200

> changes to be consistent with 2474/3260?

I was about to type "Good catch" but then I thought "Annoying catch" :-).

Two additional points:
1) RFC 3260 is a bit strange - it's Informational but purports to update
a Proposed Standard. I'm not sure that would be approved today. However,
that's a side issue.
2) RFC 3260 cites BCP 37 (RFC 2780 + several updating RFCs). Quoting 2780:

"5.2 IPv6 Traffic Class field

   The IPv6 Traffic Class field is described in [DIFF] as a 6- bit
   Differentiated Services (DS) field and a 2-bit field which is
   currently reserved.  See Section 4.2 for assignment guidelines for
   these fields."

and of course then ECN came along later, but 2780 was not updated in that
respect (I checked all the updating RFCs).

My suggestion:

DO NOT change the name of the Traffic Class field. That would confuse
everybody and invalidate several text books and many other documents.
I consider that this field is used to carry two other fields (DSCP and ECN).
The draft already says:
"  The current use of the Traffic Class field for Differentiated
   Services and Explicit Congestion Notification is specified in
   [RFC2474] and [RFC3168]."

I really don't see what's wrong with that. If we were updating RFC 791,
we'd write

   The current use of the Type of Service field for Differentiated
   Services and Explicit Congestion Notification is specified in
   [RFC2474] and [RFC3168].

I think that referring to RFC 3260 and BCP 37 would muddy the waters.
I'm not sure that many people ever look at 3260 anyway.

DO consider issuing Errata for BCP 37, which really should mention
ECN as well as Diffserv. If we were ever to do RFC2474bis, it would
be useful to adjust its language to take account of ECN too.

Regards
    Brian

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From: Tim Chown <[email-masked]>
Date: Fri, 26 Aug 2016 07:05:46 +0000

Hi,

> On 26 Aug 2016, at 00:03, Brian E Carpenter <[email-masked]> wrote:
> 
>   [RFC2474] and [RFC3168].”

I agree; a) keeping the name the same avoids confusion, and b) the text now appropriately cites the ECN usage.

Tim

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From: Bob Hinden <[email-masked]>
Date: Fri, 26 Aug 2016 12:02:42 -0700

> On Aug 26, 2016, at 12:05 AM, Tim Chown <[email-masked]> wrote:
> 
> Hi,
> 

I agree as well.

Bob