Subject: X in igmpv3 EXCLUDE(X,Y)

From: [email-masked]
Date: Fri, 20 Apr 2001 15:53:07 -0700

Hi all,

     In IGMPV3, when a router receives an exclude mode response for a group G,
it will keep state for that group in the format of  EXCLUDE(X,Y).  According to
the draft, X is the set of sources that some host would like to receive their
group G traffic but some other host is not interested in receiving their group G
traffic.
Why X is defined this way?  Why not simply keep in X the set of sources that at
least one host would like to receive their group G traffic?  With this modified
definition, transition from EXCLUDE mode to INCLUDE mode would be a lot more
smooth than the current scheme.

For example, after the following set of responses,
host 1 sends IS_IN({a}).
host 2 sends IS_IN({b})
host 3 sends IS_EX({b,c}),
the router will keep a record of EXCLUDE({b},{c}) with the current scheme.

With the modified scheme, the router will keep a record of EXCLUDE({a,b},{c}).
When the group timer expires (e.g. host 3 crashes), the router will immediately
switch the state to INCLUDE({a,b}) and possibly send some group-specific query.

Am I missing something??

Regards,
-- James Huang