All things related to multicast

[Bill Owens <>]

Although NYSERNet is on the 'good' list, something I'm happy about, 
that doesn't mean that we have good multicast deployment. One campus 
has it deployed everywhere, but it doesn't *work* everywhere; often 
when someone attempts to send or receive traffic from a new subnet 
there's troubleshooting and tweaking that has to take place. Another 
campus has multicast running just to the computer center. I have it 
to our entire network here at the NYSERNet office, but that's one 
router and one switch.

I think there are three problems preventing better deployment. One is 
that some sites' hardware just can't cut it; they have routers or 
switches that don't do anything but DVMRP, they have too many hubs, 
they have no choice but to use a firewall. Another is that multicast 
is hard to troubleshoot - it works (and breaks) differently from 
unicast, some of the troubleshooting tools are quirky and unreliable, 
there's less monitoring and alerting. The last is that it breaks, for 
me at least, on a constant basis. Every unicast routing change risks 
breaking multicast, as does every software upgrade. Even when 
*nothing* changes, multicast breaks out of spite ;)

Right now I have MSDP instablity with the Ciscos that I peer with (I 
also have a Cisco) but not with my backbone Junipers. I discovered 
that while trying to get multicast traffic from Columbia; one of 
their sources worked fine, the other didn't. Cisco problem? Bug in my 
bleeding-edge IOS? Some weird MSDP traffic? Change in unicast 
routing? Darned if I know. I'm not even positive the MSDP instability 
is related to my not being able to see their content. I'll spend a 
couple of hours troubleshooting and hopefully fix it, but next week 
or next month it will be something different.

All that being said, I do like multicast, especially native 
multicast. Things have come a long, long way since the first time I 
pulled up a multicast tunnel and they continue to get better. I will 
keep pushing it to NYSERNet members, making sure that they know both 
the benefits and the costs involved. And I've put a shiny new edge 
router in next year's budget ;)

Bill.