All things related to multicast

[John Zwiebel <>]

 On Monday, May 13, 2002, at 01:02 PM, Robert Olson wrote:
> If we could know that SSM was available on all sites' last-hop routers, and that all the OSs we use had support for IGMPv3 we'd be moving faster toward SSM (it has some nice properties we'd like to make use of...)

IMHO, if it isn't, if you move to SSM, the folks that really want to play with
you will make sure that happens.  In the mean time, that shouldn't prevent
you from being able to do both.  Moving to SSM means only:
-- including the source in the SDP information
-- having an application that knows how to take advantage of this.

Applications and hosts that can not do SSM still do exactly what they do
now.  They throw away the Source information and cause the host
to send an IGMPv2 report.

Hosts that are IGMPv3 (therefore SSM) capable that are on a network
that does not support SSM can't use the source information so just
send an IGMPv2 report.

in both cases, exactly what you are doing now.

The movement to SSM -does-not- require a "flag day".  Nor does SSM
require that you uses the 232/8 range.  If you are sending on an ASM
multicast group (ie anything other than 232/8) if the application knows
how to read the source info in the SDP message, and can send an
IGMPv3 report, there is -nothing- preventing that last hop router from
joining the shortest-path for that source.

NOR does this in anyway at all interfere with ASM hosts on other
networks.  (it depends on how the last-hop router deals with IGMPv2
hosts on a IGMPv3 'subnet' whether or not it interferes, but then you
have the same problem you have with standard ASM, how do you
allocate multicast group addresses).

There is no reason to not move to SSM.

> Any news on support in L2 switches for IGMPv3 switching? How about Linux support for IGMPv3 (last I saw the sprint code isn't being supported).
IGMPv3 snooping is easier to implement than IGMPv2 snooping.  Vendors
who haven't done so should be put out of business.

What does it take to get the sprint code "supported"?  Consumer demand.
You're a consumer, tell your Linux vendor you want it or you won't buy it.
OTOH, it isn't "supported" because no one is using it.  Taht circular thing again.

Thanks