On Wed, 2005-04-20 at 16:43 +0200, marcelo bagnulo braun wrote: > Hi, > > continuing with the topic initiated by Pekka, i guess that the next > item to discuss is whether is better to carry the context tag in the > flow id or in a new Extension header. <SNIP> > The dificulties with the Extension header is clear, i guess: > - overhead. However, it must be noted that this overhead only occurs > when there have been a rehoming event, i.e. when no rehoming has > occurred, no need for the extension header in data packets, since there > is no need to demultiplex. > the benefit of this approach is that is cleaner and that is probably > simpler (since we can use a 128 bit context tag, making sure that is > unique) > > Any additional considerations? Extension Header is IMHO the best step. Overloading the Flow label is not a good idea, if we want that then we should bump the version of the protocol and include this directly in the specification. Actually what would be preferred to me is to have a packet like: [ routing-src : 128bits / 16 bytes ] [ routing-dst : 128bits / 16 bytes ] [ site-src : 64bits / 8 bytes ] [ site-dst : 64bits / 8 bytes ] This does indeed not allow 'host' multihoming but saves 8 complete bytes. The site-src/dst could even be made optional in case the source site supports shim6 but does not do any shim6 itself (or define src=:: to specify no translation?) And people, how much 'overhead' is 16 bytes on the many megabytes that one will transfer? We are unfortunately not in the era anymore that webdesigners simply make an HTML page it has to include a lot of images, flash and other mumbo jumbo. As Marcelo mentions the above would only be sent for the first packet using this pair of addresses. Also a shim6 gate can easily drop this extension header when doing the de-multiplex/de-nat thus making this completely transparent for the outer hosts. Maybe a creepy thing: multiple 'stacked' headers like these and doing shim6-in-shim6... but let's forbid that 'feature' ;) Btw this comes awfully close to some space-port writeup I've seen once. Greets, Jeroen
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