Hi.
1. draft-metzler-ipv6-flowlabel-00 - the mechanisms proposed in this draft are not something that we should be supporting - it proposes polluting a network layer header with application layer info. If an application needs to multiplex streams onto a single socket in the way proposed it could equally well format the PDU in an appropriate way without layer pollution.
2. draft-itojun-ipv6-flowlabel-api-00 - this draft seems entirely sensible apart possibly from the desire to modify the flow label whenever the extension headers change. This should probably be under user control. Otherwise the network layer is allowed to control its own destiny whilst providing some useful information which allows routers simply to tie up the relationship between the packets of a flow.
3. The e2e mutability issue has been done to death in DiffServ for code points and it sounds like the whole argument is being trotted out again. The one and only fundamental point is that if the flow label is mutable, information is generally lost when it is changed after original setting and can never be restored unless there is some additional agency available to regenerate the information (entropy argument). If the label is changed in a way that does not lose information then it doesn't matter; likewise, if you don't care about the loss of information then go ahead and change it.
4. The flow label could clearly (also) be used as a signalling method to help out with inter-domain MPLS issues when you need to cross exchange points where the whole MPLS header has to be removed.
I concur fully with Brian Carpenter's points on orthogonality of DiffServ and MPLS. As we know some of the proposals for combining MPLS and DiffServ have an implicit (i.e. signalled during path setup) connection between label and DSCP (as opposed to just intepreting the bits in the label). This is obviously important to MPLS because if there is an MPLS header, the router (LSR) shouldn't go poking around in the encapsulated packet to determine what the DSCP is (If MPLS is used as originally intended, the payload might not be an IP packet of any kind!). So:
A. If there is an MPLS (Shim) header, that header specifies either implicitly or explicitly the DSCP to be used. The DSCP and flow label in the IPv6 header are never inspected once the packet is flowing down the MPLS path.
B. If there isn't, you could use the flow label for flowy type things (like helping with determining what MPLS path should be used at the beginning of each of, perhaps, several serially crossed MPLS domains), but the DSCP in the packet should be used to drive the DiffServ operations.
Regards,
Elwyn Davies
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Elwyn B Davies
Tel: +44 1279 405498 (ESN 742 - 5498)
Email: [EMAIL PROTECTED]
Technical Strategy Manager - IP Networks
Advanced Technology Centre
Nortel UK
London Road
Harlow
Essex
UK
CM17 9NA
"The Folly is mostly mine"
and the opinions are mine and not those of my employer.
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