All things related to multicast

[Bill Owens <>]

On Wed, Jul 19, 2006 at 10:33:08AM -0400, Ramon Sierra wrote:
> Hi,
> 
> I need help with the following problem.  All multicast streams I am 
> receiving get freeze after 4 mins or so.  If I'm the source or any of my 
> campuses is the source there is no problem.  Anyone is having the same 
> problem?  Anyone has any clue about what could be the problem?

Ramon,
        As you know, multicast forwarding relies on a great deal of state 
information in the network, and if any part of that goes away, the multicast 
traffic will stop. With this sort of behavior, it is frequently the case that 
an initial setup has succeeded, but needs to be refreshed in order to prevent 
a state timer from expiring, and that refresh doesn't take place for some 
reason. 

The trick, generally, is to watch the forwarding state at various points in 
the path from the source to the receiver, and look for it to change when the 
traffic stops flowing. It looks like you've already determined that the 
problem is no tlikely within your network, and in fact a lot of problems are 
at the edges, so that would be a good place to start. Look at PIM join state 
in particular; if it is going away or switching to a different state on one 
router, then work closer to the receiver. If it is staying the same while the 
traffic stops, work closer to the source.

Different protocols have different state timers as well, so it may help to 
get an accurate measure of just how long the stream runs from the first 
packet to the last; a capture program like Ethereal or tcpdump should be able 
to do that for you, or you could get a good guess with the clock on your 
computer. 

Bill.