[cisco-voip] Multicast MoH Delay

[Wes Sisk]

hmm,
the usual recommendation for multicast is sparse-dense which allows  
the stream to be pruned when not in use.  that said, i've not heard  
reports of delays with that setup.
you might try dense-sparse from the core and then sparse-dense at  
floor switches. if this is a propagation delay that would remove most  
of the moving pieces.

/wes

On Jun 24, 2009, at 2:46 AM, Daniel wrote:

Hi All,

I've setup multicast routing for music on hold between our data centre  
network and building floor subnets. The setup is that the data centre  
is on a different subnet and gear to the floor subnets so multicast  
routing needs to be used to get MoH packets to the phones.

This consists of the following traffic flow,

MoH Server > Access Switch > Distribution Switch/router(RP) >  
Distribution Switch/router > Floor Switches > Phones

There are three routing hops (1) from vlan interface to routed  
interfaces of distribution switch (2) between Distribution and (3)  
from routed interface of distributionswitch  to phone vlan interface.  
Only the distribution switches are layer 3.

The first distribution switch is the RP for the group and only that  
group.The second distribution switch is accepting auto RP only. We are  
using sparse mode.

Multicast traffic is working, the RP mappings are there, the mroute is  
there, the problem is that when a call is placed on hold there is a 5  
second delay before the music is heard. I assume this to be somewhat  
because of the join message and the delay of the route or path being  
setup.

Anyone know of a way to reduce the delay before music is heard? If not  
I guess its back to the lab.

regards,

Dan

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