On Sep 15, 2010, at 16:19, Fred Baker wrote: > So that might use the mesh network header part of the 6lowpan header?
That would be a bit more radical, I think (and there is no place to put a rank or instance ID in RFC 4944). But the effect is similar, as the ROLL-specific information would precede the (compressed) IP header. The difference is in handling fragmentation: in mesh-under, each fragment is l2-routed separately; here, we route entire IP packets. (The relationship of this extension header with fragmentation headers needs to be defined, but this seems quite simple to me: It only ever would appear on first fragments. If you want to do the per-fragment forwarding trick instead of reassemble-before-foward, the ROLL extension header information just goes into the tag cache together with the IP header.) Gruesse, Carsten > > On Sep 15, 2010, at 12:06 AM, Carsten Bormann wrote: > >>> Has anybody discussed adding a header with just the 3 bytes you need >>> *before* the IP header? >> >> Yes. Ever since you proposed pretty much that at a previous IETF meeting, >> I've been thinking that architecturally it makes a lot of sense to think >> about ROLL as a sub-IP protocol. >> >>> The downside is that you need a new code point (for demux) in the different >>> layer2s that you want to run this on. >> >> And that is exactly the non-starter about the general proposal. >> It is not acceptable to require a new spec for each of the many link layers >> we want to run ROLL on, in particular for those who don't really care that >> much about the overhead. >> >> However, it would be pretty easy to put something in 6lowpan to carry those >> 3 bytes. >> (Consider it an advanced form of header compression for the 48-byte IP-in-IP >> thing, if you don't like the sub-IP thinking.) >> Consult http://tools.ietf.org/html/draft-bormann-6lowpan-ext-hdr-00 for a >> sample base design. >> Such a simple extension may actually be a preferable way to carry ROLL in >> 6lowpan. >> >> Gruesse, Carsten >> >> -------------------------------------------------------------------- >> IETF IPv6 working group mailing list >> [email protected] >> Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 >> -------------------------------------------------------------------- > > -------------------------------------------------------------------- > IETF IPv6 working group mailing list > [email protected] > Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 > -------------------------------------------------------------------- -------------------------------------------------------------------- IETF IPv6 working group mailing list [email protected] Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
