All things related to multicast

[Toerless Eckert <>]

> > Hey all,
> > 
> > I'm tired of users with shared ports preventing a 100% L3 multicast
> > deployment on our campus.  More than once I've thought about just 
> > turning it on everywhere, to all of our 300 or so subnets and let the 
> > chips fall where they may.  My suspicion is that there won't be too
> > big of an effect on the shared 10 users, unless there is some highly
> > desirable multicast content.
> > 
> > So what do you all think the repercussions will be in terms of network
> > operation if we take this step?

Back in university we did this way back and as you said, it didn't pose
any  mayor problem because multicast isn't the only possible bandwidth
hog, and it is in general easier to figure out that someone monopolizes
a hub with multicast than with something else. Eg: Our hubs either
served some classroom set of workstations, and then your classmates could
easily see if someone is running a live video (which typically meant more
people would join the same channel or the studnt was asked to shut it down),
or it was a hub shared by staff and they quickly became responsible with the
applications they ran after they've stumbled across their ignorance about
the network for the first time. Now if you have single hubs connecting both
students and staff, then the self regulation of users might be a bit more of a
challenge. But in general: Sharing encourages community so it's a good
thing ;-))

By the way: when you're pinging all systems you most likely can use
the ping roundtrip time as a very good first guess when a 10Mbps
host has an overloaded collision domain.

> > Network description:
> > 6509 based L3 GE backbone, feeding 3500s and 2900s, with users connected
> > to 3500s and 2900s and still some shared 10 hubs.  Roughly 50/50 mix of
> > users on hubs and users on switches.  We ping all of the hubs and switches
> > we support (which is darn near all of them in the comm closets) every 2
> > minutes to check for reachability.
> > 
> > Tim
> > -- 
> > Tim Ward                                  
> > 
> >       V 847-467-1449
> > Manager of Operations and Engineering  G172 Leverone Hall  F 847-467-5690
> > Telecommunications and Network Services            Information Technology
> > 2001 Sheridan Rd  Evanston IL 60208-2030          Northwestern University
> >