Load balancing RTP traffic over two 1.5mb links

Unanswered Question
Jul 18th, 2009

Hello All,

I'am trying to come up with the best method to load balance RTP traffic over two 1.5 mb ATM links. Currently CEF is load balancing via source and destination ip, since the RTP traffic is between two PBX's the traffic always takes the same link. What can we do to load balance the rtp traffic? Thanks

I have this problem too.
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Joseph W. Doherty Sat, 07/18/2009 - 15:53

If your platforms support PfR, and your RTP traffic uses different port numbers per flow, then PfR might offer a solution.

Giuseppe Larosa Sun, 07/19/2009 - 10:02

Hello Jason,

the old way to do this would be to use ATM IMA to use the two links if it is only one and leaving to ATM IMA the duty of load balancing.

What Joseph suggests can be interesting if traffic has variations on UDP ports used by RTP streams and if the suggested mechanism doesn't use an odd/even check to divide flows on the links: each stream has an associated control channel and they use two consecutive ports in the range like x and x+1 with x odd bearer channel and x+1 control channel.

Just to say a L4 CEF with its way of doing would put all bearer streams on link1 and control channels on link2.

Hope to help

Giuseppe

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