Subject: Redundant channel mappings

From: Peter Johansson <[email-masked]>
Date: Wed, 15 Sep 1999 14:41:34 EDT

Thomas Narten has pointed out a subtle distinction between "overlapped"
channel mappings (described in 9.6) and "redundant" channel mappings (alluded
to in 9.7, which references 9.6).

Although they are dealt with in much the same manner (except no channel is
deallocated in the case of redundant channel mappings), the Internet-Draft is
susceptible to misinterpretation.

I suggest adding the following new clause to the next draft and to change the
reference in 9.7 to reference the new clause in place of the confusing
reference to 9.6.

"9.8 Redundant channel mappings

When ownership of a channel mapping is transferred from one multicast source
to another, it is possible for more than one device to claim ownership. This
results in redundant MCAP advertisements, transmitted by different sources,
each of which specifies the same multicast group address and channel. A
procedure similar to that of 9.6 SHALL resolve the contention for channel
ownership.

Multicast channel owners SHALL monitor MCAP advertisements in order to detect
redundant channel mappings. MCAP advertisements whose expiration field has a
value less than 60 SHALL be ignored for the purpose of redundant channel
detection. When a redundant channel mapping is detected, the owner with the
largest physical ID (as determined by the least significant six bits of
source_ID from the GASP header) is NOT REQUIRED to take any action. The
owner(s) with smaller physical IDs SHALL cease transmission of MCAP
advertisements for the redundant channel number but SHALL NOT deallocate the
channel number."

I will be the first to admit to editorial laziness in this solution. It would
be superior to write a new clause, 9.X Overlapped and redundant channel
mappings, and locate it after current 9.7. If anyone feels STRONGLY that it
should be written that way, speak up---you just might be able to overcome my
inertia.

Regards,

Peter Johansson

Congruent Software, Inc.
98 Colorado Avenue
Berkeley, CA  94707

(510) 527-3926
(510) 527-3856 FAX

[email-masked]

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From: "Hattig, Myron" <[email-masked]>
Date: Fri, 17 Sep 1999 07:27:58 -0700

Does this text satisfy concerns and not introduce new concerns?

Thanks,

-myron