Subject: Questions on response to MCAP Solicitation Request ...

From: Prabhakara Yellai <[email-masked]>
Date: Wed, 7 Oct 1998 14:16:21 PDT

Hi,
   When a specific multicast recipient transmits an MCAP solicitation
   request, why should the corresponding multicast channel
   owner(s) to broadcast an ADVT message instead of sending
   the ADVT message directly to the requestor ('directed ADVT')
   with the required multicast address to channel mapping (not
   all mappings owned by that node).

   Sending directed ADVT avoids unnecessary processing of ADVT
   messages by other nodes (anyway, other nodes have to process
   the ADVT messages from a node as often as that node sends :-)).
   In addition, sending the ADVT with the specific channel
   mapping results in conserving both bandwidth and CPU cycles.

   I went back to the draft while typing this mail. When I reread
   the sections 10.2 and 10.3, it appreared to me that, it is
   not mandatory for a node to respond with an ADVT message to
   a Solicitation request (there is no separate section on
   processing solicitation messages). IMHO, it should be made
   mandatory to respond with a broadcast/directed ADVT
   to a solicitation request. If it is not, and a node chooses
   not to send an ADVT message, it is possible that a multicast
   transmitter sends the multicast data on the default channel
   for, in worst case, 10 seconds.

   I don't believe these approaches haven't been discussed before
   and I would like to know the reasons why they were discarded.
   Appreciate your response.

Prabhakar

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From: "Hattig, Myron" <[email-masked]>
Date: Fri, 9 Oct 1998 13:21:34 -0700

Prabhakara,

>    mapping results in conserving both bandwidth and CPU cycles.

Anytime broadcast is used it may be a considered a bug or a feature.
Your points show its use for MCAP as a bug.  I consider it a feature
because it is the best way to prevent unnecessary solicits or
advertisements. The lack of frequency with which advertisements
or solicits are being sent causes me to think there are no packet
processing performance problems.

>    for, in worst case, 10 seconds.

Good catch. This was an earlier issue I thought was resolved, but
searching back through the spec on the string 'olicit', I don't see
the statement that a mapping owner should respond immediately
after receiving a solicit msg. I'll add it to the list.

>    Appreciate your response.

I don't recall if the discussion took place in IETF meetings, or on
the reflector, but I recall briefly discussing unicast/broadcast
MCAP. You can see the results of the discussion in the spec. ;-)

-myron