VOIP Priority

[ddbadinger]

I am trying to setup priority for voice on a cisco router. I have used the 'ip rtp priority' command and am unsure about the last option 'bandwidth'. I am not quite sure what to put there. Is it a calculated number or is it set to my per call bandwidth off of my phone switch or is it another number?

Thanks for any input.

[dumartin]

The bandwidth statement is the amount you will want set aside for high priority. So if you went-

16384 16383 24 ....you would allocate 24k for the PQ. It is freed up when there is no priority traffic to use it.

[ddbadinger]

If I have my router configured like this:

map-class frame-relay VoIPovFR

no frame-relay adaptive-shaping

frame-relay cir 64000

frame-relay bc 600

frame-relay be 0

frame-relay mincir 64000

frame-relay fair-queue

frame-relay fragment 80

frame-relay ip rtp priority 16384 16383 60

How is the 60k used if I have 64k allocated for cir? Is that too much or too little?

[pborelli]

Setting BW = 60k (on the ip rtp priority command) means that you are reserving up to 60k for *RTP* traffic, when such traffic is present. Is has nothing to do with your CIR. This value should match the necessary BW to hold the maximum number of simultaneous calls, and it depends on the codec each call will use. For example, G.729 will take about 26k on a FR link (without cRTP). So 60k would allow for 2 concurrent calls, and there would be a little cushion (of 60 - 52 = 8k). Don't forget that RTP priority means strict priority; if you have, in this case, 2 concurrent calls, you will have too little BW for data during the time the 2 calls are active.