Margaret,
On Aug 5, 2009, at 08:12 MDT, Margaret Wasserman wrote:
Hi Joel,
On Aug 4, 2009, at 10:51 PM, Joel M. Halpern wrote:
The problem is not what the ITRs and ETRs use the field for. They
could / can use the field.
The problem is that the UDP header was introduced specifically so
that different flows would be different in a place that the routers
would look when doing ECMP calculations.
And the router to date do not use the flow label.
Preliminary indications are that routers also won't use UDP-lite,
because it is a different protocol, and they don't know it has port
numbers.
The simple path forward is to allow UDP with 0 checksum.
If that is incorrect, then finding the correct path forward is
going to be hard.
We're talking about the ECMP calculations in _IPv6_ routers here,
right? Do you really believe that enough IPv6 routers have shipped
with this sort of ECMP behavior in _hardware_ that we need to
consider that legacy deployment? I'm somewhat skeptical that this
could be the case... If we're going to make design compromises to
deal with currently-deployed hardware, I'd like to see some evidence
that this hardware actually exists in numbers that are worth
considering.
Note, I'm not asking how many routers have been shipped that support
IPv6, nor am I asking whether those routers support ECMP (in
software). I'm not even asking whether some router vendors have
taped out versions of silicon that are so inflexible that they will
only support IPv6 ECMP using UDP ports (not the flow label or UDP-
Lite)... What I am asking is whether IPv6 routers containing that
silicon exist in real-world deployments in large enough numbers that
they should be considered in our design choices.
Take a look at the following URL:
http://www.sixxs.net/faq/connectivity/?faq=ipv6transit
(Note, I can't vouch for the accuracy of the entire list, but it's
about the best publicly available list I've seen).
That list includes some very large networks.
-shane
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