> On Apr 19, 2021, at 1:50 AM, Stephane Bortzmeyer <bortzmeyer@xxxxxx> wrote: > > On Sun, Apr 18, 2021 at 11:42:28PM -0400, > Phillip Hallam-Baker <phill@xxxxxxxxxxxxxxx> wrote > a message of 100 lines which said: > >>> You have described the messages only, which alone has never been >>> enough to define a protocol. >> >> Usually that is the case. But IP is a rather peculiar >> exception. There is lots of stuff above and lots of stuff below and >> there is the routing layer out to the side. But what is there to the >> packet layer except the packet format > > I agree with you (that IP does not really fit the traditional > description of a "protocol", for instance it does not have a state > machine, explicit or implicit) but the same could be said for > Ethernet, which was a protocol once but now is only a format. There is a state machine; most of it is degenerate*, but there’s definitely state associated with at least fragmentation reassembly. *the core state is quite complex in its rules, i.e., net in -> net out includes hop count processing, check for destination accept, ECN marking, DSCP prioritization, and HBH extension processing net in -> user out includes ECN relay to transport, E2E extension processing including reassembly user in -> net out includes source address determination, DSCP and ECN setting, E2E extension processing including fragmentation And don’t forget the receipt and generation of ICMPs, RAs, NDs, etc. Joe
