pls explain the description of IP header compression

[llongb1]

1005 packets, 64320 bytes

30 second offered rate 16000 bps, drop rate 0 bps

Match:any

compress:

header ip rtp

UDP/RTP Compression:

Sent:1000 total, 999 compressed,

41957 bytes saved, 17983 bytes sent

3.33 efficiency improvement factor 99% hit ratio, five minute miss rate 0 misses/sec, 0 max

rate 5000 bps

this the information descrbing the ip

header compression, pls some guy can explain what's mean about the "3.33 efficiency improvement factor ", if I want to explaint the ratio of IP header compression to customer , through that information , what can I get from ?

[Kevin Dorrell]

IP compression and cRTP compression is a way of making your link more efficient. It is particularly effective when you have a small payload in each packet, for example if you are using G729a codec on your phones. When you have a very small payload, most of the packet is taken up with IP and RTP headers. However, the contents of this headers is quite predicatable, so there is great scope for saving bandwidth be compressing them. If you can reduce the headers from their normal 36 bytes (if I remember correctly) down to 4 or 5 bytes, then that is a big space saving.

The 3.33 efficiency improvement means that instead of using 16000 bps, you have been able to compress it down to 1/3.33 of its size, i.e. about 5000 bps. That's a pretty impressive improvement.

Be aware that with header compression, the headers have to decompressed in each router and recompressed on the outgoing link. They cannot pass through the router without the compression, usually on the CPU, getting involved.

Kevin Dorrell

Luxembourg