[cisco-voip] advantages of fax relay over fax passthrough?

[Lelio Fulgenzi]

Thanks Matt. You mention "...if you want to support the fastest speeds in faxing." 

Not sure what you mean by that, because as far as I can tell, with Cisco fax relay, SG3 speeds are not supported. Things are changing with IOS 15 (but I think that affects passthrough speeds as well). 





--- 
Lelio Fulgenzi, B.A. 
Senior Analyst (CCS) * University of Guelph * Guelph, Ontario N1G 2W1 
(519) 824-4120 x56354 (519) 767-1060 FAX (JNHN) 
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 
Cooking with unix is easy. You just sed it and forget it. 
- LFJ (with apologies to Mr. Popeil) 


----- Original Message ----- 
From: "Matthew Ballard" <mballard at otis.edu> 
To: "Lelio Fulgenzi" <lelio at uoguelph.ca>, "cisco-voip voyp list" <cisco-voip at puck.nether.net> 
Sent: Monday, April 19, 2010 2:15:54 PM GMT -05:00 US/Canada Eastern 
Subject: RE: [cisco-voip] advantages of fax relay over fax passthrough? 




>From my study on the matter, relay (Cisco or T.38) is absolutely better if passing through any type of WAN link or other type of link where latency or jitter can be an issue, or if you want to support the fastest speeds in faxing. Since relay is IP, and was designed with the potential unreliability of IP in mind, it can handle that type of issue in a much cleaner method. 



It is also potentially important if you have a fax server that uses IP, as it will likely use T.38 (it is important for analog VoIP ports to support T.38 in this case if you want to allow internal faxing between an analog port and a fax server, and you will need gateway support enabled at a minimum). 



Passthrough is easier to implement (and less likely to encounter bugs), but more prone to network issues, as it is simply passing the analog signal (and fax/modem is much more sensitive to any disruptions to the signal), and is supported on more equipment in more protocols (for example last I checked standards based T.38 isn’t supported with SCCP gateways, only MGCP and H.323). Also, the ATA-186 (not the best box for faxing anyways) only does passthrough. 



Personally I ended up using standards based T.38 wherever possible (I have 2 ATA-186s doing faxing at this point, although I have plans to change that) to ensure consistency for our fax setup, since we do have a fax server and remote sites on WAN links. 



Matthew Ballard 

Network Manager 

Otis College of Art and Design 







From: cisco-voip-bounces at puck.nether.net [mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Lelio Fulgenzi 
Sent: Monday, April 19, 2010 10:49 AM 
To: cisco-voip voyp list 
Subject: [cisco-voip] advantages of fax relay over fax passthrough? 




can anyone help me understand the advantages of fax relay over fax passthrough. 

>From what I gather, if our network is high speed, low latency, low jitter, we should look at using passthrough since it's the easiest to configure. 

Why should I use fax relay? 

--- 
Lelio Fulgenzi, B.A. 
Senior Analyst (CCS) * University of Guelph * Guelph, Ontario N1G 2W1 
(519) 824-4120 x56354 (519) 767-1060 FAX (JNHN) 
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 
Cooking with unix is easy. You just sed it and forget it. 
- LFJ (with apologies to Mr. Popeil)
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