
RTP
Table 56: Anatomy of
IP header | UDP header | RTP header | 20 ms of G.729 audio |
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20 B | 8 B | 12 B | 20 B |
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It is important to understand that all
Network perspective
RTP header compression is a mechanism that routers use to reduce the 40 bytes of protocol overhead to approximately 2 to 4 bytes. Cisco routers use this mechanism, as does the Avaya X330WAN router, which is a module for the P330 chassis. RTP header compression can drastically reduce the IP Telephony bandwidth consumption on a WAN link when using
Recommendations for RTP header compression
Enterprises that deploy routers that are capable of this feature might be able to benefit from it. However, Cisco recommends caution in using RTP header compression on its routers because it can significantly tax the processor if the compression is done in software. Depending on the processor load before compression, enabling RTP header compression can significantly slow down the router, or cause the router to stop completely. For best results, use a hardware/IOS/ interface module combination that permits the compression to be done in hardware.
RTP header compression has to function with exactness or it will disrupt audio. If for any reason the compression at one end of the WAN link and decompression at the other end do not function properly, the result can be intermittent loss of audio or