[cisco-voip] SIP t.38 fax

[Brian Turnbow]

Thanks Nick, 
This seems to be related however to h.323. I know that with h.323 I can set the rate and I assumed that this was the case for SIP, but now I 'm not so sure . In the "configuring fax" guide (firt url)  it talks about setting the fax rate, but then says 64k I've tried asking my local cisco rep and I'll let you know if I get a answer. 
Brian
 

________________________________

From: Nick Marus [mailto:nmarus at gmail.com] 
Sent: venerdì 3 giugno 2005 15.33
To: Brian Turnbow
Cc: cisco-voip at puck.nether.net
Subject: Re: [cisco-voip] SIP t.38 fax


Interseting you mentioned this for I was having to look this info up this week as well and found this article:
 
http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121newft/121t/121t3/dt_t38fx.htm
 
What I understood is that it varies depending on the fax rate command. If you use fax rate voice it will take 64k, but if you use faxrate 9600 it only uses 24k.
 
Excerp:
Note   The fax call will not get compressed using the ip rtp header-compression command, because User Datagram Protocol (UDP) is being used and not Real-time Transport Protocol (RTP). For example, 9600 fax call will take about 24 kbps. 


 
On 6/3/05, Brian Turnbow <b.turnbow at twt.it> wrote: 


	Hello All, 
	I  am look ing to deploy a SIP network that needs to support fax and looking into t.38 I found 

	SIP T.38 Fax Relay 

	*T.38 fax relay requires a 64-kbps transmission rate, the same amount of bandwidth as a voice call with the G.711 codec. 

	http://www.cisco.com/en/US/products/sw/iosswrel/ps1839/products_feature_guide_chapter09186a00800b5dce.html <http://www.cisco.com/en/US/products/sw/iosswrel/ps1839/products_feature_guide_chapter09186a00800b5dce.html>  


	Do you need 64k for a fax transmission with via sip using a cisco gateway ? 

	Thanks 
	Brian 


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-- 

Nick Marus
nmarus at gmail.com
homepage: http://www.nicholasmarus.com

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