Subject: [magma] MLDv2: operation without state change reports: periodic queries

From: Erik Nordmark <[email-masked]>
Date: Fri, 14 Feb 2003 18:28:22 +0100 (CET)

I see nothing in section 6 which says that the router periodically does
a general query and how it rebuilds the state from that query.

The only loose reference is in 6.4.2 which says:
   Routers must query sources or multicast addresses that are requested
   to be no longer forwarded.  When a router queries or receives a query
   for a specific set of sources, it lowers its source timers for those
   sources to a small interval of Last Listener Query Time milliseconds.
   If multicast address records are received in response to the queries
   which express interest in listening the queried sources, the
   corresponding timers are updated.
and this doesn't mention periodic queries!

Are periodic queries not needed?

The above text also seems to only apply to listeners in INCLUDE state.
For those it is sufficient to reduce the lifetime in the source list
and send a query, which the resulting current state records increasing the
lifetime of the source list entries that are in use (and adding any missing
ones). Thus this will allow those INCLUDE source list entries that
are no longer used by any listener to time out quickly.

However, the "lowers its source timers" can't apply to the EXCLUDE state
list since those source timers are already zero perf section 6.4.1 (B)!

What seems to be needed to recover the state of the EXCLUDE listeners
is something like the following procedure:
 - create a temporary EXCLUDE source list which lists all possible
   sources (can be implemented by treating the first report differently
   than subsequent reports)
 - send a query for the multicast address (or a general query)
   and retransmit as usual
 - all IS_EX (and presumably TO_EX) reports received during the
   query interval are used to form the intersection in this temporary EXCLUDE
   list
 - at the end of the query interval replace the current EXCLUDE list with
   the temporary EXCLUDE list

I don't see anything in section 6.4 that seems to say this.
Is this because it isn't believed that periodic queries are needed?

There is a vague reference to having temporary state in 6.4.2 4th paragraph
but that wouldn't help be implementing the above type of scheme.

What am I missing?

  Erik

_______________________________________________
magma mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/magma