Subject: RE: The Assert Mechanism

From: "Shekhar, Ravi" <[email-masked]>
Date: Wed, 20 Oct 1999 21:45:58 -0400

> >this assumes that the assert winner takes responsibility for 
> >local group members, but don't existing pim implementations 
> >do that?
> 
> The spec states that the assert winner takes over.

  Isidor, you are right. Section 2.9 states that. And it would
  work as long as all the PIM routers on the LAN are also running 
  IGMP.

  But section 3.2.1 Periodic J/P point 1.2 

           2 The outgoing interface list in the (*,G) or (*,*,RP)
             entry is non-NULL, or the router is the DR on the same
             interface as the RPF neighbor.

  talks about sending joins even when oif list is NULL and RPF is 
  on the same interface as DR. If all the routers on the LAN are running
  IGMP and know about local group memberships, is there a need for DR to 
  send such joins?
  Last hop router (RPF nbr presumably in this case if there are no
  other joins) can take care of it.
  
  So then I assumed that probably this is done to take care of cases 
  where all the routers on the LAN may not be running IGMP (but DR 
  is running IGMP). And if that is the case, then assert-winner 
  might not come to know of local group memberships existence/withdrawl. 
  And DR would be responsible for sending/not-sending joins to assert-winner

  based on local group membership.

  - Ravi Shekhar.

---

From: Isidor Kouvelas <[email-masked]>
Date: Wed, 20 Oct 1999 20:11:44 -0700

>  other joins) can take care of it.

This is done for the case when the DR is a downstream router. In this case it
creates a (*,G) state because of the IGMP report but it cannot add the
interface to the olist as it is the (*,G) incoming interface. However it still
has to generate joins.

>  based on local group membership.

Normally all routers receive IGMP reports. The difference is that only the DR
should act on the reports unless an assert happens in which case another
router may take over.

Isidor