All things related to multicast

[Alan Buxey <>]

hi,

unfortunately, many sites just dont 'get' multicast (well,
logically and physically) . there are a few tools out there
for checking/testing but i seem to recall that all of the 
eg beacon software monitors have fallen out of support.

we entered into a system in which an IPTV system was delivered
to campus via multicast. really nice - the students could
watch many channels...and of course, only one stream per
channel chewed up our WAN link..... not many sites could
take up such a system so the company changed their client
to do receive unicast streams instead... (granted, they have
an adaptive compression system with client feedback loop)
but now each viewer sucks up the bandwidth. thats just a shame :-(

maybe the situation will change now that we have these
new GLOP IP addresses for multicast - it gives sites the chance
to use an address fairly easily and know that there should
be no clashes with others.

as for the tech/takeup... its one of those techs which on the local
network is often common...on the LAN is not needed (broadcast
can take over...and sites do directed broadcast to deal with
leaky needs etc)...and its one of those that is often blamed
for issues..with a 'just turn it off' mentality - which now seems
to be targetted just the same at IPv6 :-(

..it doesnt help when software vendors dont read the specs and just
abuse it... i've lost count of the number of packages that
use a global multicast address...and TTL of 255!! :-(

alan