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Exercises for the interested readerExercises for the interested readerPosted Dec 4, 2010 7:22 UTC (Sat) by paulj (subscriber, #341)In reply to: Exercises for the interested reader by mxkb Parent article: Ghosts of Unix past, part 4: High-maintenance designs
I've heard people with experience of building hardware-forward routers complain about the same thing - that the IPv6 "Next-Header" daisy chain is a pain to implement (in hardware specifically, was their complaint). I don't understand yet why though - IPv4 options *also* use a TLV format, and the v6 payload length includes the options just as v4's length does. What am I missing?
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Exercises for the interested reader Posted Dec 7, 2010 0:50 UTC (Tue) by mxkb (guest, #71646) [Link]
Extension headers are considered part of the payload. So even from ipv6 header, you can get payload length, you still have to parse every extension header to find the TCP/UDP header. The difference is in IPV4, you can find the L4 header directly.
Exercises for the interested reader Posted Dec 7, 2010 10:41 UTC (Tue) by paulj (subscriber, #341) [Link]
Yes, I can see how some might dislike that, but it only applies to end-hosts. So doesn't affect routers, unless I'm missing something? (Indeed, making it more expensive for middle-boxes to unpack and get at the ULPs might even be a good thing in some respects).
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