On Thu, 26 Sep 2002, Caitlin Bestler wrote: > On 9/26/02, Lloyd Wood wrote: > > >On Wed, 25 Sep 2002, Fred Baker wrote: > > > >> At 01:12 PM 9/25/2002 +0100, Lloyd Wood wrote: > >> >A datagram is self-describing; full source and > >> >destination. A fragment (IPv4 fragment) may not be. > >> > >> you sure? take a GOOD look at RFC 791... It is > >> completely self-describing in terms of getting itself > >> there and where it belongs in the reassembled datagram. > >> If the other bits and pieces don't arrive, there is > >> another matter, but it is at that point a host issue, > >> not a forwarding issue. > > > >I'm not sure that following fragments relying on a bit in > >another fragment saying 'following fragment' is truly > >self-describing. > > > >(Not having port nos in following fragments would only be > >a host issue if routers and firewalls never peeked at > >ports en route.) > > So, as originally proposed an IP fragment is a fully > self-routed L3 datagram. well, not self-routed; you need routing state. I don't think the difference between routing table state and circuit-switched state is all that great; anything beyond hot-potato is fundamentally stateful. ICMP doesn't work well on fragments either - only on fragment zero. Following fragments can't be described by ICMP. That's not a host issue. Anyway, forget 'datagram'. I'd like to know where use of the term 'self-describing' for something that requires description in RFCs and implementations and ridiculous numbers of textbooks ever came from. L. > However, in the de facto world of merged L3/L4 routing > (with NATs, load balancers, etc.) it is dependent on state > information and hence is not a datagram. > > However, the term was applied before L3/L4 "routing" came > into existence. So the term 'datagram' was correct. And of > course nobody would change the term ex post facto. This is > why these terms are indeed fluid and nebulous. > > - > This message was passed through ietf_censored@carmen.ipv6.cselt.it, which > is a sublist of ietf@ietf.org. Not all messages are passed. > Decisions on what to pass are made solely by Raffaele D'Albenzio. > <http://www.ee.surrey.ac.uk/Personal/L.Wood/><L.Wood@ee.surrey.ac.uk>