Subject: RE: Doubts PIM

From: "L.N.Subramanian" <[email-masked]>
Date: Wed, 22 Mar 2000 14:12:28 +0530

-----Original Message-----
From:	Bill Fenner [SMTP:[email-masked]]
Sent:	Tuesday, March 21, 2000 9:32 PM
To:	[email-masked]
Cc:	[email-masked]; [email-masked]
Subject:	Re: Doubts PIM

>   I dont understand the the second condition in 1 b? How it helps in 
>sending Periodic Join Message.

It allows a "downstream" DR with no downstream group members (so it
has an empty OIF list) to still send Joins to get traffic to the
network it's the DR for.  Bad ASCII art:

        RP
        |
        R1
        |
        R2
        |
    -----------------------------------   
                 |                   |
                 H                   DR

In this case,it's the DR's job to get the traffic from the RP since H
is interested, but the DR has an empty oiflist so the first half of
1b would prevent it from sending a join to R2.
[L.N.Subramanian]  How can a DR distingish between the groups it has learnt from downstream host-group members and
                                that learnt in the other interface as Host H is,
  i.e;
              1      2
       H1------R1---------R2
                         |
                       H2

suppose say R1 is the DR on interface 1 & 2.
Host H1 joins for group G1
(*,G1) at R1

  iif           oif    
  2             1
From H2 for G2
  2             -        [oif = NULL  right?]
 
suppose H1 takes its membership out of G1, then

(*,G1)

  iif =2    oif  = Null
Now will R1 send Join for group G1? It sends Periodic Join for G2. How does it distinguish between Groups learnt
from different interfaces when the Oif = NULL.

>2)   With what Version of IGMP does PIM can operate?

Any.

>      And if Querier in IGMP v2 is diiferent from DR on the LAN, then how
>does the DR knows about Group Information.

That's how IGMP works; non-Queriers know group membership also.

  Bill