question of ip rtp header-compression

[teru-lei]

Hi all,

when use VoIP, the default codec is g.729, and the pure data rate is 8k, but when I use rsvp to check, the rsvp preserve 24k per session. Is the overhead (24-8=16k) is all rtp overhead? If so, and I use ip rtp header-compression command in the interface, how many bandwidth can I save with this command? can any body tell me? thank you!

Best Regards

Teru Lei

[ndoshi]

The use of G.729 coder-decoder (codec) allows the compression of voice calls to 8 kb. However, VoIP networks introduce header-based overhead, which raises the size of the voice packet to 60 bytes and the required bandwidth to approximately 24 kbps. The use of compressed real-time protocol (cRTP) reduces the size of the header to 2 to 4 bytes per packet and the bandwidth requirement to 11.2 kbps per G.729 compressed call (Figure 4), thus increasing call capacity.

http://www.cisco.com/en/US/about/ac123/ac114/about_cisco_online_exclusive09186a00800a34b3.html

Nilesh