OT? cRTP header compression

Thu Apr 11 03:55:19 UTC 2002

Hello Thomas

I had some kind of experience doing cRTP over Cisco routers, we use Cisco
7204 & 7206 Routers on the IP Gateways and Cisco's 3600 and 5300 as VoIP
gateways, as well we had a small setup using a Cisco 2611 router on the
termination router.

The trick is change the VoIP payload size of each packet to reduce the
packets per second in a half improving the  performance over the routers,
also we are using as Cisco recommends TCP & RTP headers compression over the
circuits using only MLPPP encapsulation.

Also please note that using cRTP and Compression you have increased the
switching delay over the circuit and for that reason you may need also to
have more processing power of the router.

Below you can see a Cisco site where you can check the recommendations for
this setup and also based on that information I created a Bandwidth
calculator on an excel sheet, if you want it, just drop me an email, I will
send it you.

http://www.cisco.com/warp/public/788/voice-qos/voip-mlppp.html

http://www.cisco.com/warp/public/788/pkt-voice-general/bwidth_consume.html

http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fqos
_c/fqcprt6/qcfcrtp.htm

http://www.cisco.com/warp/public/105/compression-qos.html

Bye

Antonio J. Pena
Manager, Network Engineering

(  /_ _ _  __/_ _ 
|_/(-/ (-_) /(//  
Verestar, inc.
1901 Main street
Santa Monica, CA, 90405
Phone(310)382-3300
Direct(310)382-3409
antonio_pena at verestar.com
http://www.verestar.com

-----Original Message-----
From: Thomas Kernen [mailto:tkernen at deckpoint.ch]
Sent: Wednesday, April 10, 2002 1:11 PM
To: nanog at merit.edu
Subject: OT? cRTP header compression

I'm looking for real world experience related to deploying cRTP header
compression on Cisco routers related to VoIP flows. We are trying to
evalute what type of hardware (ie: CPU power since cRTP is CEF switched
since 12.2x IIRC) is required to handle 96/192/384 VoIP calls over a
single circuit (HDLC/PPP/FR). This is related to specific overseas
circuits where the cost of the circuit is still very expensive vs the
cost for the extra hardware to handle the header compression. I'm
disregarding all QoS info at this stage.

Cheers
Thomas