[no subject]

Cheers
Thomas

----- Original Message -----
From: "Mathew Lodge" <mathew () cplane com>
To: "Pena, Antonio" <Antonio_Pena () verestar com>; "'Thomas Kernen'"
<tkernen () deckpoint ch>; <nanog () merit edu>
Sent: Thursday, April 11, 2002 1:47 PM
Subject: RE: OT? cRTP header compression


> At 08:55 PM 4/10/2002 -0700, Pena, Antonio wrote:
> > 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.
>
> As well as increasing sample size (thereby increasing the
payload:header
> ratio), the other thing to try is turning on voice activity detection
(VAD,
> AKA silence suppression). For human conversation, this typically
reduces
> packet rates by around 60%, enabling you to squeeze more conversations
onto
> the link. It also has the side effect of reducing CPU utilization per
call
> on your Cisco voice gateways. Note that turning on VAD does decrease
the
> perceived voice quality a little, so whether it is worth it depends on
> where you want to make the trade-off between cost and voice quality.
>
> Also, cRTP is not CEF switched on the 5300 in 12.2, AFAIK. It was on
> 26xx/36xx, but 5300 architecture (and hence switching code) is
different.
> That may have changed since I last looked 6 months ago -- best bet is
to
> ask on the Cisco-NAS mailing list at
>
> http://www.cisco.com/warp/public/471/cisco-nas.html
>
>   Cheers,
>
> Mathew
>
>
>
>
> > 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.h
tml
> >
>
> 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 () verestar com
> > http://www.verestar.com
> >
> >
> > -----Original Message-----
> > From: Thomas Kernen [mailto:tkernen () deckpoint ch]
> > Sent: Wednesday, April 10, 2002 1:11 PM
> > To: nanog () 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