Sander Steffann wrote: > Hi, > >> My question to th wg is: >> >> 1) Do we want to limit the size of the IPv6 header chain? > > I think it is necessary yes. > >> 2) If so, which limit should we pick? > > I think there are two conditions here: > - The full layer-4 header must be within this limit, and it must be in the > first fragment (if fragmented at all) > - The limit should be larger than what is currently used + some margin for > stuff we forgot > > Take i.e. Figure 3 of > http://www.cisco.com/en/US/technologies/tk648/tk872/technologies_white_paper0900aecd8054d37d.html > as example. It shows a Mobile-IPv6 packet: IPv6 header (40 octets) + Routing > header (24 octets) + Destination Options header (24 octets) + Fragmentation > header (8 octets). Add to that a basic TCP header (20 octets) and we arrive > at 116 octets. > > So a limit of 128 would currently probably be ok, but I personally would > prefer the limit to be a bit higher just to have some extra margin. > > Cheers, > Sander > I've been trawling through various standards trying to identify sane extension header combinations myself.
I've come across a couple of problematic standardised options already defined that don't appear to have individual length limits below the overall generic limit of 256 octets per option (derived from the "Opt Data Len" field being 1 octet), so limiting the overall header length to 256 octets could have direct impact on those. PadN (of course) The lineID option rfc6788. The Routing Protocol for Low-Power and Lossy Networks (RPL) Option rfc6553 regards, RayH -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
