[cisco-voip] SIP analog gateways

[Daniel Pagan]

Definitely a valid point on ECM -  it can help with a few errors detected on transmitted page, but consistent errors will simply cause ECM to retransmit again, and again, until the fax fails, redials, detects more errors and repeats the retransmissions, fax failure, redial, repeat again, etc.
Adding to this, you can disable ECM from a Cisco voice gateway when using fax relay. When using pass-through, this can’t be done in IOS and must be done on the fax machine itself, but fax relay has the capability to the ECM “advertisement” from the destination fax machine’s DIS, which is basically a series of tones communicating its capabilities (ECM being one of them). If this gets stripped from the DIS, the originating fax machine will simply think ECM isn’t supported and will never negotiate it when sending its DCS.

This done on the terminating gateway:

For SIP/H.323
  voice service voip
   fax-relay ecm disable

For MGCP
  no mgcp fax t38 ecm

Hope this helps.

- Dan

From: Ryan Huff [mailto:ryanhuff at outlook.com]
Sent: Wednesday, August 19, 2015 10:53 AM
To: nhaas at co.fresno.ca.us; Daniel Pagan <dpagan at fidelus.com>; norm.nicholson at kitchener.ca; cisco-voip at puck.nether.net
Subject: Re: [cisco-voip] SIP analog gateways


My experince is that analog faxing over SIP is sometimes a dance.

What I have found to work consistently is to disable SuperG3 and ECM on the fax modem and restrict the rx/tx of the modem to 14.4 Kbps.

Thanks,

Ryan


-------- Original Message --------
From: "Haas, Neal" <nhaas at co.fresno.ca.us<mailto:nhaas at co.fresno.ca.us>>
Sent: Wednesday, August 19, 2015 10:31 AM
To: 'Daniel Pagan' <dpagan at fidelus.com<mailto:dpagan at fidelus.com>>,"'norm.nicholson at kitchener.ca'" <norm.nicholson at kitchener.ca<mailto:norm.nicholson at kitchener.ca>>,"'cisco-voip at puck.nether.net'" <cisco-voip at puck.nether.net<mailto:cisco-voip at puck.nether.net>>
Subject: Re: [cisco-voip] SIP analog gateways
We tried to put our faxes all on SIP, best solution was to move 200 DID’s back to PRI, sad day…….

Thank you,
Neal Haas


From: cisco-voip [mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Daniel Pagan
Sent: Wednesday, August 19, 2015 5:52 AM
To: norm.nicholson at kitchener.ca<mailto:norm.nicholson at kitchener.ca>; cisco-voip at puck.nether.net<mailto:cisco-voip at puck.nether.net>
Subject: Re: [cisco-voip] SIP analog gateways

I personally can’t speak to 3rd party FXS gateways, but I’ve worked with customers in the past whose VG224s were integrated w/ CUCM via SIP trunk. The two caveats that immediately come to mind are applicable to a non-Cisco FXS gateway using SIP as well:


1)      Lack of SCCP supplementary services

http://www.cisco.com/c/en/us/td/docs/ios/voice/fxs/configuration/guide/15_1/fxs_15_1_cg_book/fxssccpsplmft.html

2)      Unable to use shared line appearances between the VG2XX and non-VG2XX device.

Just two things to keep in mind. I’ve seen this sometimes act as a deal breaker w/ SIP to the FXS gateway. Hope this helps in some way.

- Dan

From: cisco-voip [mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of norm.nicholson at kitchener.ca<mailto:norm.nicholson at kitchener.ca>
Sent: Tuesday, August 18, 2015 7:10 PM
To: cisco-voip at puck.nether.net<mailto:cisco-voip at puck.nether.net>
Subject: [cisco-voip] SIP analog gateways


Anyone using a SIP FXS gateway instead of a VG224. Just trying to compare costs and ease of use.

Thanks



Norm Nicholson
Telecom Analyst
City of Kitchener
(519) 741-2200 x 7000


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