On Thu, 15 Apr 2010, Joel M. Halpern wrote:
There seem to be two separate things going on here, and they appear to be
getting mixed.
The first thing is the notion that the host should set a non-zeero value into
the flow label. They should do so with the constraint that different packets
which are part of the same flow MUST have the same flow label. And flows
which the end host is willing to have treated (even if treated may mean
simply in terms of which link in a LAG or ECMP selection is used) differently
may have different flow labels.
However, a network can not give QoS treatment purely on the basis of source
and dest IPv6 address plus flow label. There simply is not enough
information. A client provided flow label is not a DSCP code point.
So networks that want to do QoS will have to do something additional. What?
That depends upon what they want to do. I would hope that whatever they do
it does not destroy the granularity of the flow label as described above.
If we can count on hosts setting the flow label with suitable granularity,
then we can use the flow label (plus src and dest IPv6 address) in our ECMP
and LAG hashes without having to look for protocol and port numbers. That
avoids much complexity related to next headers and similar problems. And it
is not subject to an attack by someone mis-setting the flow label field.
I understand similarly as you. Best Regards,
Janos Mohacsi
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