Subject: draft-ietf-ipv6-flow-label-00.txt

From: Thomas Narten <[email-masked]>
Date: Fri, 15 Mar 2002 16:21:03 -0500

Hmm. There was much discussion in SLC on the Flow Label.  Quite a lot
of mail in the weeks immediately after SLC. Then quiet. Then a new ID
appears. More silence. Something like 45 minutes of agenda time has
been allocated next week for the topic. Has no one had time to read
the draft yet? :-)

Here are some high-level comments for folks to think about.

The scope of the document could be narrowed. I think its focus might
better be just what a host and router MUST do in order to be
compliant. There is a fair amount of additional text that talks about
MAYs with regards to possible usages. 

It could say more about what a host is supposed to do. It says a host
MAY set the flow label, for instance, rather than what it MUST do. I
think it would be better for the document to say a HOST just sets it
to 0. Or, if that is not right, what it SHOULD/MUST do. We want
predictable behavior from the originating hosts.

In fact, the document might just have too many MAYs. It seems like it
is trying to not make it illegal for someone to experiment with the
flow label. I'm OK with that, but that doesn't need to be put in the
spec as MAYs. It should be clear what RFC-compliant implementations
are supposed to do. Not sure it needs to say anything more. People are
always free to experiment.

There is perhaps too much wording about what signaling (and "methods")
should do with the flow label. IMO, much (all?) of this is future
work, and this document shouldn't constrain it in anyway. For example,
there may well be too much wording about how one might use the flow
label. For example, there is wording about allowing the receiver to
tell the sender what flow label should be used. This seems premature.

There is even wording that suggests classifiers need to handle
wildcarding of the source and dest fields in the tuple. Not sure how
much of that is appropriate.

In summary, I think it would be good for this document to make it
clear exactly what compliant hosts and routers MUST do. Trying to say
anything more than that may tending towards speculation that is
premature.

Thomas
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From: "Tony Hain" <[email-masked]>
Date: Fri, 15 Mar 2002 13:54:31 -0800

Thomas Narten wrote:
> Has no one had time to read
> the draft yet? :-)

No, but thanks for the reminder & comments.

Tony

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From: Brian E Carpenter <[email-masked]>
Date: Sun, 17 Mar 2002 19:02:27 +0100

> It says a host

But we can't do that realistically. A host may choose to set the flow
label on no traffic at all, on particular types of traffic that it cares
about, or on all traffic (unlikely). This will be a matter of local policy
configuration, and/or the level of QOS support available in that particular 
version of that particular operating system. 

What this document attempts to say is what should happen in cases where hosts
*choose* to activate the flow label. So the whole document is inevitably
a MAY. Perhaps it would be better if that was explicit - an applicability
statement written as a MAY, but SHOULDs in the body of the text to define
the desired behaviour.

Thanks for reading it anyway!

   Brian