RFC3697 [Re: [RRG] FLOWv6: IPv6 Flow Label to control DFZ forwarding]

[Brian E Carpenter <brian.e.carpenter@gmail.com>]

Robin,

> 1 - We would replace the current semantics of the Flow Label:
> 
>       http://tools.ietf.org/html/rfc2460#appendix-A

That appendix is non-normative and effectively obsolete. Please see
RFC 3697. (Unfortunately, this doesn't show in the RFC index as an
update to 2460, since the appendix is non-normative.)

You will find that the bounding semantics of the flow label
are quite well defined in 3697. The history is that there was
a very clear consensus in the IPv6 WG that the semantics
should be defined strictly end to end between hosts; use as
a routing handle was explicitly set aside.

I can't assert that there is no use of the flow label, since
it has consenting-host semantics. On the other hand, no use cases
have been documented to RFC level since RFC 3697 came out,
and I've never seen any statistics or traces indicating
non-zero flow labels. The flow-aware router people planned
to use it at one stage, but that is now caught up in ITU-T
process following on ITU-T Y.2121 (see
draft-adams-tsvwg-flow-signalling-codepoint-00). I don't
know for sure if they still plan to use the flow label.

So, if the mechanism you propose (I haven't read further
as I type this) is incompatible with the bounding semantics
in RFC 3697, quite some work in the IETF would be needed
to resolve this.

    Brian

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