Thanks for the response, Brian.

> > Are there reasons for preferring to put a flow label inside the
> > IPv6 header?  Is this being done on the advice of folks who are
> > standardizing label switching technologies?
> >
>No, because it has nothing to do with label switching. It's much 
>more to do with QOS than routing. We know how to use the draft-rajahalme-
>label for Intserv and Diffserv, but it may well have other QOS
>usage as well. It's end2end property is vital for that and completely
>different from the swappable MPLS-type label.

But, I still don't understand why an IPv6 QoS/diffserv flow label 
is "completely  different" from an MPLS-type label...

I do understand that MPLS labels are swapped at each intermediate
node, and that IPv6 flow labels will not be.  What are the other
differences?

Will we still use the IPv6 destination address in each packet to 
determine the next-hop router?  Or will routers set-up state 
regarding the next-hop associated with each flow label?  

If the former, then I understand the difference.  An intermediate
router would need to read the IPv6 (or IPv4) header, anyway, in
order to forward the packet.  The IPv6 flow label would just be
some additional information to influence packet queuing or 
processing.

However, if the latter (routers save next-hop state based on flow
labels), wouldn't it be better to develop a mechanism that could
work with both IPv6 and IPv4, so that routers will not have to 
behave differently for IPv6 and IPv4 packets?

If I seem to be missing an important point or concept, please send
some hints or pointers.

Thanks,

Margaret




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