Multicast Traffic on Backbones

Sun Jun 10 07:30:58 UTC 2001

On Sat, 9 Jun 2001, Tim Winders wrote:

> UUnet has two levels of multicast capabilities.  Their "Basic" package is
> receive only and is free.  Their "Gold" package is full send/receive, but
> they charge a ton for it.  The basic package seems pretty useless to me.
> To join a multicast group, you have to be able to send to it, right?

not right. with many/most multicast protocols, you can (sometimes must)
build a source-rooted tree, not a shared tree. joining as a receiver
is then a matter of becoming another branch off the tree, hopefully
along the reverse shortest path to the sender. in this case, you can
send but not receive.

possibly the difference is in your permissions to establish a (s,g) pair
or to announce a core (RP).

which multicast routing protocols are on offer? PIM-SM? MSDP? MBGP?
if you can't get your multicast across the border, it may not be useful
to you.

there are better protocols in the literature than are deployed
but the arcana is often politically anathema for inertial, commercial
or plain lack-of-working-code reasons.

> I have found that most sales reps don't know what multicast is, or why it
> is important to have.

many network engineers glaze over at the mention of multicast. it
takes some serious grey matter work to fathom the entire subject.