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New Member

RTP header compression and policy maps

There has always been a problem, getting the bandwidth correct, when using

a policy map, we have to allow about 26kbps per G729 call, within the policy-map, but then when using the frame-relay ip rtp header-compression, it gets compressed to 11.6Kbps, for example we want 5 concurrent calls on a 128kbps link, in the Policy-map that would be 130kbps which is over the 128k, and doesn't allow any bandwidth for the we have had to say the bandwidth was more than 128k for things to work.

I see with 122-13T there is now class based RTP& TCP header compression

which overcomes this problem... Has anybody used this yet? If I have one router running an earlier release of IOS with the frame-relay IP rtp Header compression, will that work with a router running the new class based header compression?

any comments most welcome, and a Happy new year to everybody.

New Member

Re: RTP header compression and policy maps

Answeriing my own question

managed to do some testing this is the policy map applied to a frame relay interface

policy-map 256kCIR

class VOIP-RTP

priority 280

compress header ip rtp

class VoIP-Control

bandwidth 10

class class-default

police cir 240000

conform-action transmit

exceed-action drop

here is the sh frame pvc 200 showing the policy map traffic, one voice call no other traffic

Class-map: VOIP-RTP (match-any)

5838 packets, 373632 bytes

30 second offered rate 25000 bps, drop rate 0 bps

Match: ip precedence 5

5838 packets, 373632 bytes

30 second rate 25000 bps

Match: ip dscp ef

0 packets, 0 bytes

30 second rate 0 bps


Strict Priority

Output Queue: Conversation 40

Bandwidth 280 (kbps) Burst 7000 (Bytes)

(pkts matched/bytes matched) 5839/373696

(total drops/bytes drops) 0/0


header ip rtp

UDP/RTP compression:

Sent: 4850 total, 4849 compressed,

184259 bytes saved, 106741 bytes sent

2.72 efficiency improvement factor

99% hit ratio, five minute miss rate 0 misses/sec, 0 max

rate 8000 bps

You can see the the 30sec offered rate still says 25000 bps, and after compression the max rate was 8000bps

when i did ahow interface you see it is about 12000bps

30 second input rate 11000 bits/sec, 52 packets/sec

30 second output rate 12000 bits/sec, 52 packets/sec

So the problem is still not fixed, I still have to allow 25k for each call in the

policy- map even though it is really only taking 12k, that means when the policy-map is created I cannot put the true CIR, i have to fudge it to make it work.

anybody else know of anything different.