On 12/06/2013 11:58, 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.
I think we should advocate 256 as a target for hardware designers; we know that
some of them have current hardware limits less than that, but a "SHOULD inspect
256"
seems reasonable (and conversely, a "SHOULD NOT exceed 256" for hosts generating
IPv6 packets).
Given time (as somebody said, maybe ten years) this would palliate the
problem.
Brian
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