Subject: Prioritized ports (was: M-Bone losses into the UK)

From: Ross Finlayson <[email-masked]>
Date: Fri, 22 Nov 1996 21:23:10 -0800 (PST)

I wrote:
>I've never been thrilled with these ad hoc port priorities in mrouted.
>
>As they're not defined in "Assigned Numbers", and native multicast routers
>don't implement them (I presume), maybe they should be dropped from future
>versions of mrouted?

And Bill responded:
>Until real resource reservation comes along, we have to be able to do
>something.  The default rate limit was a mistake, but the existence of
>rate limits and the ad-hoc classifier was not.

Yes, I was probably going too far in calling for the elimination of
prioritized ports in "mrouted".  It seems that they perform a useful
function.  (Note, BTW, that I wasn't arguing against rate limits.)

My main concern is really their 'ad hoc' nature - in particular, the fact
that the priority mechanism is not standardized, nor is it implemented in
any other routing implementation other than "mrouted" (although I may be
wrong about this).

I'm also not sure that "resource reservation" (by this I assume you meant
RSVP) will always be the right alternative for priorities.  Priorities seem
to be a reasonable mechanism for systems which are tolerant of bandwidth
degradation, with the priorities (in effect) indicating the relative
'tolerance' of each medium.  (On the other hand, some media - most notably
audio - will certainly require a minimum bandwidth to be useable.)

Anyway, enough rambling...

        Ross.