All things related to multicast

[Dan Pritts <>]

On Sat, Jan 12, 2008 at 01:21:04PM -0500, Alan Crosswell wrote:
> - What do we do about multicast over WiFi networks?  We are looking at
>   systems that distribute entertainment content to students in their
>   dorm rooms, and, as we all know, students don't use wired networks
>   anymore.  What are the issues with various vendors' WiFi products and
>   multicast snooping, pruning, rate limiting, etc.?

I tried this back in the 802.11b days with a mix of apple airports
and cisco 350s.  Even when i rate-limited multicast to 512kbps the
network was unusable.

I believe this was because 802.11a/b/g all drop down to the speed of
the slowest client associated to the AP when sending broadcasts, and
they made no attempt to do anything more intelligent with multicast.

the slowest data rate in the 802.11b spec is 1Mbps; I guess the 512k of
multicast i sent plus all the 802.11 MAC layer stuff was just too much.
if i recall correctly, 802.11 is pretty chatty to prevent stations from
stepping on one another.

Looks like the lowest rate in 802.11g is 6Mbps (assuming you disable b 
compatibility).  Probably not good enough for IPTV, i assume you'd need
to support several 2-4Mbps streams?

I should be able to attend the BoF.

danno
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Dan Pritts, System Administrator
Internet2
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