Subject: RE: The Assert Mechanism

From: "Mohit Talwar (Exchange)" <[email-masked]>
Date: Wed, 20 Oct 1999 17:28:57 -0700

> > >In PIM Dense Mode, the outgoing interface is "pruned" and a timer is
> > >associated with it, so that Asserts reoccur periodically to handle
> > >failures like this.  Perhaps PIM-SM could use a similar mechanism.
> >
> >to avoid the periodic reflood upstream of the
> >assert loser, the assert winner can periodically re-assert as long as
> >there is traffic for the source.
> 
> You mean the winner would retransmit its Assert before the loser's
> timer goes off to refresh the timer?  (If the loser doesn't have a
> timer then this doesn't help any when the winner dies).
> 

correct me if i am wrong...
but this solution requires another timer per oif per tree entry
and periodic generation of control (assert and joinprune) messages.

what do u think about the alternative in which the DR on an 
interface keeps track of tree entries for which it has lost 
the interfacec and the neighbor to whom it lost it. so the 
interface can be added to those entries if the assert winner 
dies.  

this assumes that the assert winner takes responsibility for 
local group members, but don't existing pim implementations 
do that?

anyway, i think the spec should say something about this so
implementations are consistent.

mohit.

---

From: Isidor Kouvelas <[email-masked]>
Date: Wed, 20 Oct 1999 17:47:46 -0700

>interface can be added to those entries if the assert winner 

This would only work if you can also detect that state has been cleared
by configuration on the assert winner. To achieve this the GenID in
Hello messages should change when state is cleared as well as on
restarts.
In either case, as Bill pointed out, on the loser you have to maintain
information on the interface after you have stoped forwarding (keeping
it in the list in pruned state).

>local group members, but don't existing pim implementations 

The spec states that the assert winner takes over.

>implementations are consistent.

Agree. A fix for this problem should go in the spec.

Isidor

---

From: Liming Wei <[email-masked]>
Date: Wed, 20 Oct 1999 19:30:32 -0700 (PDT)

> From: Isidor Kouvelas <[email-masked]>
> 

This is what the spec says about the DR losing assert:

   From then on,
   the DR is no longer the last-hop router for local receivers and
   removes the LAN from its (*,G) oif list. The winning router becomes
   the last-hop router and is responsible for sending (*,G) join
   messages to the RP.

> Agree. A fix for this problem should go in the spec.

If it is broken, we'v got to fix it. No question about that.

Lets concentrate on coming up with a good description of the problem,
and have a well described/understood proposal for the fix.  If I
missed the complete description for the proposal, please resend
it to me. Thanks.

-Liming