Re: NHRP/MARS version number location.

[Grenville Armitage <[e-mail]>]

Tim,

>>With all due respect, I think you missed my point completely.

Well, if missing the point is a euphemism for disagreeing with you then
yes, I missed the point. Unfortunately I'm going to continue to
miss your point, because I think it is being too narrowly applied.

>>You are "overlooking" what is meant by "version."  MARS Version 1 has a
>>format which is well known.

If _you_ want to call it "MARS Version 1" and "NHRP Version 1" on
your purchase orders then go right ahead. But they are versions 0
and 1 respectively of the newly established family of address
resolution/mapping protocols whose control messages are uniquely
identified by LLC/SNAP codepoint of [0xAA-AA-03][0x00-00-5E][0x00-03].

>>However, I don't think that you or anyone
>>else knows what the format of the MARS Version 2 messages will be,
>>including the format of the Version 2 "fixed header."

Good grief. Maybe its my head cold, but I get a wierd feeling
about this argument. What do you mean I dont know what your "MARS Version
2" fixed header will be like? That's exactly my point - it will be
the same as the "MARS Version 1" fixed header. The fixed header contains
the generic information that, to the best of our predictive abilities,
will be required by any major revisions to the MARS (or NHRP) protocols.
I happen to think its a perfectly acceptable fixed header (hmm, stating
the obvious, I know :-) If we develop some new fangled address resolution
protocol in the future I've got no doubt the current fixed header
fields will be just fine.

>>In other words,
>>your "fixed header" ought to be viewed as fixed within MARS Version 1,
>>not as fixed in perpetuity across all versions of MARS and across
>>all address resolution protocols.

Please be careful with such sweeping statements. I made it quite
clear in the previous email that its fixed across all address resolution
protocols that choose to identify their control messages with the LLC/SNAP
codepoint of [0xAA-AA-03][0x00-00-5E][0x00-03]. If you truely find yourself
constrained by the current 'fixed header' as you develop "MARS Version 2"
then by all means complain bitterly to <someone who owns an OUI> and
define a new LLC/SNAP codepoint. You wont need to, in my opinion,
but nothing is stopping you.

>>My argument is that nearly every other Internet protocol makes provisions
>>for graceful migration to the next version, (which could possibly have
>>a different message format), by placing a protocol version number early
>>in the message.

I get the impression you simply dont like the idea of such a big fixed
header.

>>I haven't seen any argument that MARS is somehow different than the
>>rest of the Internet protocols and therefore shouldn't have a version
>>number fairly early in the message.

The fixed header is fairly early in the message. Trite, but true.

	[..]

>>So, it appears that what you have been calling a "version" number is
>>really a protocol identifier.

Ummm - bit like the IP version number, which basically identifies
a number of incompatible protocols, you mean?

	[..]
>>This strategy also constrains the next address resolution protocol
>>we invent to use the MARS header format.

If you mean the _fixed_ header format, yup. And to restate
(for the benefit of the archive trawlers who'll come across this
thread sometime in 1997 while trying to invent the next address
resolution protocol) if the current fixed header is _so_ painful - find
another LLC/SNAP codepoint.

>>I simply don't think
>>our powers of prognostication are good enough to have invented the
>>ultimate address resolution message format.

Fortunately we're only prognosticating about the fixed header.
Lucky that, eh?

cheers,
gja