Subject: RE: IGMPV3: Source timer expiration in Exclude Mode

From: Srivatsan S <[email-masked]>
Date: Fri, 4 Oct 2002 10:00:54 +0530

EXCLUDE mode is "forwarding packets from *all but* specific source
addresses".

When you remove the source (with timer expired) from the list, multicast data
packets from that source are forwarded to that i/f (whereas it should be
blocked). Only the sources with "source-timers expired and in the block list"
are blocked in EXCLUDE mode. Packets from all other sources are forwarded. 

Refer Appendix A.3 in the draft for more explanation. 

- Srivatsan

----------------------------------------------------------
Srivatsan S
MindTree Consulting, Bangalore.
Ph: 91-80-6711777 Extn:1428
----------------------------------------------------------

-----Original Message-----
From: Suresh Boddapati [mailto:[email-masked]]
Sent: Thursday, October 03, 2002 9:08 PM
To: Srivatsan S; idmr
Subject: RE: IGMPV3: Source timer expiration in Exclude Mode

Not sure this helps. Maybe you can elaborate. My question relates to the
second entry in your table. I have a source timer that has become zero (or
expired) in EXCLUDE mode. The draft says that I should not remove the source
record (even though I should block forwarding of packets from this source).
My question is what is the use of keeping this record around? Why not just
delete it? We delete the record with source timer zero in INCLUDE mode
because we dont need it anymore. Same thing applies to EXCLUDE mode also
(even from your explanation, since everybody on the network is in agreement
that no one needs packets from this source).

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]On Behalf
Of Srivatsan S
Sent: Wednesday, October 02, 2002 8:35 PM
To: suresh; idmr
Subject: RE: IGMPV3: Source timer expiration in Exclude Mode

Suresh,

     Following table gives u a more clear picture.

   Mode                      Source Timer

  EXCLUDE             If source timer is running, then there is a
                      conflict for the source, i.e., one client wants
                      mcast packets from the source, while another doesn't.
                      Hence the result is if source timer is running in
                      EXCLUDE mode, the mcast packets from the source are
                      forwarded to the n/w. It is the responsibility
                      of the client to filter out unwanted packets.

  EXCLUDE             No source timers are running. The clients in this
                      n/w are in total agreement that they don't need
packets
                      from this source.

  INCLUDE             Source timer should be running. Because if the source
                      timers are not running, there is no point in keeping
                      the entry as it is obvious that none of the clients
                      are interested.

    Also, note that in EXCLUDE mode if any igmp packets are received which
contains
    sources to be blocked, these are not blocked immediately. A Group and
source
    specific query is sent to make sure that none of the clients on the n/w
wants
    packets from the source. At this point of time, the mode is EXCLUDE with
    source timer running. If no response is received, the timer expires
blocking
    the source. If a client responds, the source timer continues to
    run with all mcast packets from the source being forwarded to the
interface.

    Hope this helps.

Thanks,
Srivatsan

----------------------------------------------------------
Srivatsan S
MindTree Consulting, Bangalore.
Ph: 91-80-6711777 Extn:1428
----------------------------------------------------------

-----Original Message-----
From: Suresh Boddapati [mailto:[email-masked]]
Sent: Wednesday, October 02, 2002 9:55 PM
To: idmr
Subject: IGMPV3: Source timer expiration in Exclude Mode

Hi,
	In the table specified in Section 6.3, when a source timer expires in
EXCLUDE mode, it says "DO NOT Remove Record". I am assuming this means the
source record. If so, what is the use of keeping the record and not removing
it as is done when the mode is INCLUDE? When the group timer expires and the
transition happens to INCLUDE mode, all the source records that have expired
timers are removed anyway. Why keep them till the group timer expires?
Thanks.

Suresh

---

From: Suresh Boddapati <[email-masked]>
Date: Fri, 4 Oct 2002 09:03:30 -0700

Thanks for the explanation. I think I understand what you are saying,
although IMO the spec could have been a little more explicit. I guess it is
more easier conceptually and consistent with the draft's notation if it
stated that
"when a source timer expires in EXCLUDE mode, IGMP should suggest to not
forward traffic from source and move source from the INCLUDE list to the
EXCLUDE list"  i.e.

Original state      Src Timer expired       New state
==============      ===============         ==============
EXCLUDE(X, Y)              (A)              EXCLUDE(X-A, Y+A)

Does this sound right?

Suresh

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]On Behalf
Of Srivatsan S
Sent: Thursday, October 03, 2002 9:31 PM
To: suresh; idmr
Subject: RE: IGMPV3: Source timer expiration in Exclude Mode

When you remove the source (with timer expired) from the list, multicast
data
packets from that source are forwarded to that i/f (whereas it should be
blocked). Only the sources with "source-timers expired and in the block
list"
are blocked in EXCLUDE mode. Packets from all other sources are forwarded.

- Srivatsan

-----Original Message-----

Suresh,

   Mode                      Source Timer

    Hope this helps.

Thanks,
Srivatsan

-----Original Message-----
From: Suresh Boddapati [mailto:[email-masked]]
Sent: Wednesday, October 02, 2002 9:55 PM
To: idmr
Subject: IGMPV3: Source timer expiration in Exclude Mode

Hi,

Suresh