Clustering over WAN - Design question

Unanswered Question
Oct 2nd, 2009


I have read the SRND-section of clustering over WAN and i have a question about bandwidth requirements: SRND states, that you need 1,544 Mbps minimum for sites that are clustered over WAN for ICCS real-time traffic. It says "sites" not "servers".

And you need additional 1,544 Mbps for every subsriber server remote to the publisher for database traffic. Here it says "server" not "sites".

Why is the real-time traffic independant of the number of servers at a site? I thought, the real-time traffic is fully meshed between each server running ccm.exe, so if i have 2 remote subscibers at a site, i would assume that i would have 1,544 Mbps to every other server running ccm.exe. So in a 2 site environment with 2 subsriber at each site i would have 4 ICCS-real-time-traffic flows, each with 1,544 Mbps. Is that correct?

I have this problem too.
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Paolo Bevilacqua Fri, 10/02/2009 - 03:13

I think all what the document tries to convoy, is that the more the servers and sites, the more the bandwidth you need.

I do not think an exact requirement can be ever calculated, because ultimately it also depends by the volume of traffic.

So if like in the networking of today you can provide BW in good amounts between sites, you should not have any problem. You also needed that media streams anyway, so it's not like you can save on it.

philippgrafl Fri, 10/02/2009 - 04:00

It is clear that the bandwidth needed depends on the volume of traffic. But the 1,5Mbps at 10.000 BHCA are already calculated for a high call volume in respect of the installation we did so far. The key point for me is, we start with 2 sites, but there will be more sites with a subscriber. So if i add another site, do i also have to increase the bandwidth to the other remote sites (which is true if there is a 1,5Mbps "stream" to each server) or is it OK to provisioning enough bandwidth to the main site, where publisher is located.

Paolo Bevilacqua Fri, 10/02/2009 - 04:27

I would start with the initial sites, watch circuit utilization, add BW as necessary.

Good networking is done going trough the the reality of things, not papers.

blatkinson Fri, 10/02/2009 - 03:14

For the DB replication, I believe the subs only get DB updates from the pub.

Good question on the real-time signaling traffic requirements. Maybe Cisco was pointing more toward DB replication needs. That would be a lot of BW dedicated to just signaling.


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