On Mon, Apr 19, 2021 at 9:26 AM Joseph Touch <touch@xxxxxxxxxxxxxx> wrote:
> 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.
+1
Behcet
Joe
