Has anyone use rtp header compression?

ilcram19-2ilcram19-2 Senior MemberBanned Posts: 436
in CCNP Collaboration
tcp header compression or ip rtp header compression?
im using g.711 for my remotes offices that only have 1 ip phone, im getting an average of 110 to 120kb per call i know g.729 take about 30-40k but they want the best posible voice quality, would the compression compress the voice packet a good amount of size of it really stays the same?
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  • cisco_troopercisco_trooper Member Posts: 1,441 ■■■■□□□□□□
    I'm not a voice expert, but if I remember correctly the header compression you are talking about doesn't affect the voice payload, but affects only the packet headers. Someone please correct me if I'm wrong...this is good information to know.
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  • kryollakryolla CCIE Bound Member Posts: 785
    what the speed of the link. Header compression is just that it compresses the IP, UDP and RTP header but you only have 1 ip phone. Are you using dial up lol. I would be more concerned about bigger packet taking too long to get on the wire on a slow serial link than header compression for 1 phone especially G.711. It will compress the the headers from 40bytes to 2-4 bytes. what is you sampling rate 10ms? G.711 with a 10ms sample will go from 80k to 64.8k. You can't have the best of both worlds, slow link and best quality one has to give. Are you using QOS for voice packets? Check out VOIP bandwidth calculator
    Studying for CCIE and drinking Home Brew
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  • ilcram19-2ilcram19-2 Senior Member Banned Posts: 436
    the links go from dsl to cable and the speed is abou 256kup, im gonna give it a try, it doesnt drop any packets or anything i have also a shaper apply to the interface and im givin 125k for voice so is about 50% of the bandwith i just wanted to save some bandwith that all
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  • networker050184networker050184 Went to the dark side.... Mod Posts: 11,962 Mod
    ilcram19-2 wrote: »
    the links go from dsl to cable and the speed is abou 256kup, im gonna give it a try, it doesnt drop any packets or anything i have also a shaper apply to the interface and im givin 125k for voice so is about 50% of the bandwith i just wanted to save some bandwith that all

    You will need to have cRTP configured on both sides of the link and I believe it is only supported over PPP, HDLC and Frame Relay serial links so that would rule out your connections.
    An expert is a man who has made all the mistakes which can be made.
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  • mrblackmamba343mrblackmamba343 Senior Member Inactive Imported Users Posts: 136
    compression must be done at ends of the connection. Try using the MQC instead of the old way.

    class-map VOICE
    match protocol rtp

    Policy-map VOICE
    class VOICE
    Compression header ip rtp

    inter s1/0
    service-policy output VOICE


    you can even prioritize voice traffice by using the priority command under the policy-map
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