All things related to multicast

[debbie fligor <>]

At 6:01 -0700 10/25/05, Russ Hobby wrote:
> Hi All,
>
> I have been asked a question from a researcher who's project has 
> been trying to use multicast for some time with many problems, and 
> she asked me "Are we trying to do the impossible?"
>
> Their particular use of multicast relies on multiple multicast 
> connections and for them to be set up in a timely fashion.  It is 
> the setup time for a connection with which they have been having 
> trouble.  Connections can take up to several minutes to be 
> established.  They have worked the problem out with a couple of 
> campuses and a gigapop to get it to work (which had to wait for new 
> router codes to be installed in several places).  However every time 
> they go to a new site, they are likely to have the problem again and 
> they have to work it through those network engineers.

Sounds like what happens on our campus.  we don't have any campus 
multicast applications, and didn't even know changing our core from 
cisco to foundry router had broken pim sparse... 3+ years of patches 
and debugging later I think pim is finally stable on this platform, 
and of course we're ready to start swapping out the equipment for 
newer.  (We still have mbgp/msdp issues, but we're considering going 
to a new border router vendor to fix that).

So occasionally a product or application is brought in, and we think 
it should work but it doesn't.  right now campus is working but our 
beacon sources aren't being seen outside of a few sites -- probably 
all MREN peers.  I haven't done enough troubleshooting to mail any 
provider or msdp  peer yet, since half the time this kind of outage 
is on our end.

We are trying to make multicast a service, but without a broken 
application when it's down to keep it a priority (for us and the 
vendor) it's been hard to do.  once we have the new hardware in place 
we're going to see if we can get something using multicast regularly 
on campus so it is more visible as a production part of our network.

> So the researcher is asking if they should give up on multicast and 
> redesign their application.  What do you think?

i like the try multicast fail over to unicast approach as being the 
best compromise, but that doesn't work for all applications.

> Russ


--

-debbie
Debbie Fligor, n9dn       Network Engineer, CITES, Univ. of Il
email: 

          <http://www.uiuc.edu/ph/www/fligor>
"Every keystroke can be monitored. And the computers never forget."