Subject: SPT switch case.

From: "Shekhar, Ravi" <[email-masked]>
Date: Tue, 2 Nov 1999 14:44:28 -0500

I was wondering if the following situation is covered
  somewhere in the draft or do we need to update Periodic
  Join/Prune section to cover it. 

   RP
   |             S
   .             .
   .             .
   |             |
   R1            R2
   |  I          |
   ---------------
       |host

  R1 is the DR/LHR and there is a local group membership on
  interface I for group G. 

  R2 is the next hop towards S for R1.

  If R1 decides to initiate the switch to SPT for <S, G>, it will 
  create an <S, G> entry with iif as I and oif list as NULL (as 
  the only oif I here is also the iif).
  It should trigger an <S, G> join regardless of oif list being 
  NULL in this case or else switch will not happen. Periodic J/P
  section currently prevents the <S, G>join to be generated if the 
  oif list is NULL.
  (This is very similar to the related problem of RP initiating the 
   switch even when oif-list is NULL).

  Thanks.
  - Ravi Shekhar.

---

From: Nair Venugopal <[email-masked]>
Date: Tue, 2 Nov 1999 23:09:15 -0800 (PST)

> On Tue, 2 Nov 1999, Shekhar, Ravi wrote:

>  Join/Prune section to cover it. 

Could one use the text in Section 3.2.1.1 (Trigger-ed Join/Prune Messages) 
to trigger this (S,G) Join?

   "A  Join/Prune message is triggered if and only if a) a new entry
    is created, or b) the oif list changes from null to non-null or
    non-null to null ..."

An implementation could create a new (S,G) entry with NULL-OIF, trigger
the (S,G) Join and then perhaps delete the (S,G) entry because of
zero-downstreams. 

If this was the intent, perhaps the text in the spec could be updated.

--Venu

--------------------------------------------------------------------
Nair Venugopal  --- [email-masked] --- 3Com WAP Engineering

---

From: [email-masked] (Billy Ng)
Date: Wed, 3 Nov 1999 09:36:17 -0500

> From [email-masked] Wed Nov  3 02:17:22 1999
> 

well, you don't want to delete the (S,G) entry because you need that
for the periodic join message.  I would consider this a special case
and should be stated in the spec.  Can the authors look into updating
this?

--Billy