Another comment on the extension header orders...
What we need is a more deterministic approach to build the daisy chain of
headers. Because we cant have the different flavours and it is very
difficult as it is when we have to parse all the extension headers to get to
the transport header (which is useful for layer 4 classification)...
This is no problem if you do it in a sw based router where you have all the
time in the world to parse your header but it becomes an issue when you
implement IPv6 in asic!!
Have people thought about/What do people think about changing the length
field and replacing it with a (IP) header length field (the basic header +
the extension headers) and have a mandatory payload length in the last
extension header (transport header + payload)? (one flag that tells if the
packet is decode with an ESP header where packet classification on layer 4
info is useless - of course:-)
This would really make it easier to mask out the offset in the basic header
towards the transport header (which simply would make up to the loss of the
protocol field that we had in IPv4) without having to have too wide packet
decoding (which becomes a real problem when you have to go over 300 bytes in
oc-768 speeds and above)
And I would also like to define a mandatory limit on the length of the IP
header incl extension headers.
What do people think?
-- thomas
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