Hi,

is there a maximum number of multicast groups that routeros can handle? If so, is it hardware dependent.

We're thinking about multicast in our organization, and are concerned at the number of systems that start multicast groups - think Mac OS X Laptops, and other bits of software. Just wondering if a single central router dedicated to multicast would be able to handle the load.

FWIW: 4k isn't enough..

thanks,

Hello,

Think there is no restrictions from ros side. The only limitation will be the power of hardware vs concurrent multicast groups can handle. Routing takes a power. traffice itself is limited by network. What is the number of multicast groups it needs to handle and in what bitrate ?

I have 150 concurrent multicast streams in action and my hw is core2 duo 2.8Ghz and the load is ~40%

The bottleneck will be the switches - they have a limitation in multicast groups!


Kind regards

Aleksander

I honestly don't think there's a software based router out there that could handle 4,000 multicast groups unless the vast majority of those groups is just empty. The router doesn't just have to route the packets for those groups, it has to process them. To get anywhere close to that number you're going to need something that can do multicast forwarding and replication in hardware.

I guess my question really was there any limits software wise in ros - the problem that's been seen is things like Mac OS X systems that start multicast (bonjour) for service discovery and advertisement - so there might be lots of really small groups with only 1 or 2 members at most. So lots and lots of small, "unused" groups.

The problem I've seen with some of the hardware routers, is the limit (in hardware) is 4k entries (or less if you're running virtual router instances).

Bounjour runs on 224/24, which is confined to a single subnet. There's no multicast routing for Bonjour services. It runs entirely on 224.0.0.251, so there's only one group. There may be one such group behind every router interface, but the router doesn't have to participate in it since theres' no expectation of anyone that the traffic be forwarded past the local subnet.