Multicast Advice

[kschafer]

Hello,

We've been using Tandberg video encoders in unicast mode to transmit video streams over IP from encoders in one city to a single decoder in another city. We'd now like to convert the IP stream to multicast so that multiple decoders in various locations can participate.

The encoders and decoders are in multiple cities and each city has a 3550-EMI switch that I'd like to use as a gateway. The interconnection between switches is Gig-E.

What I'm contemplating is having each encoder/decoder in its own VLAN local to the city/switch and 1 single multicast VLAN tying all the switches together.

I'm also thinking that I'd like each encoder to use the local switch as the RP. Do I need to hard code this or should I just let Auto-RP choose ? I'm not clear on what role the RP actually plays.

Our switch topology is a tree with encoders and decoders existing at arbitrary locations on the tree. Obviously I'd like the streams to split appropriately at each intersection.

Any pointers or suggestions would be appreciated.

Thanks,

= K

[scottmac]

The RP (Rendezvous Point) is the root of the multicast tree (closest to the point of origin).

Depending on whether you are using PIM-dense, PIM-Sparse, or PIM Sparse-Dense, you may or may not need an RP.

For example, if you use PIM Sparse-Dense: If an RP is defined, PIM-Sparse will be used. If no RP can be determined, then PIM-Dense mode will be used.

Sparse / Dense refer the initial distribution and subsequent pruning of the multicast "branches."

The "branching" will happen according to IGMP as each client requests access to the multicast stream. If the client drops / goes away, a timer expires, and the multicast stream to that port is "pruned."

Goood Luck

Scott

[kschafer]

OK, it sounds like it makes sense to manually set the RP since in every case I will know which switch should be the appropriate root for a particular group. (listeners can be anywhere but the senders for a particular group will always be on a particular switch in the origin city)

Also, are you aware of any multicast timers that may need adjustment ? I've had some success with multicast thus far but it seems the stream never lasts longer than a day. ie, when I leave work, the stream is working but when I come back in the morning, the picture has frozen indicating that the decoder stopped receiving traffic.

Thanks,

= K