FAX T38 Redundancy: what it means ?

Endorsed Question
May 13th, 2009

Hi,

There are a setting: FAX T38 Redundancy in spa2102 in LINE tab. How it works?

Some time SPA2102 do not detect that is a fax, and do not do a ReInvite with T38. How can I better set up SPA2102 to detect fax ?

Best Regards

Przemek

I have this problem too.
0 votes
Endorsed by Dan Lukes
Patrick Born about 7 years 8 months ago

Hi Przemek,

Great question. This feature is not documented. I had to request this information from Engineering. I will let the docs group know to update next time they revise the ATA admin guide.

Voice tab > Line N tab > Audio Configuration > FAX T38 Redundancy:

The number corresponds to how many previous packet payloads are repeated with each packet.  Zero means no payload redundancy.  Default is 1 (which matches previous behavior, that is we have been using redundancy = 1 all along).  The higher the number, the larger the packet size and hence the larger the bandwidth consumed.  This is independent of packet rate.

The Admin Guide describes configuring T.38 faxing in detail on page 55 in the Using a Fax Machine section.

Available from: https://www.myciscocommunity.com/docs/DOC-2149

Direct link: http://www.cisco.com/en/US/docs/voice_ip_comm/csbpvga/ata/administration/guide/ATA_AG_v3_NC-WEB.pdf

Regards,

Patrick

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Patrick Born Wed, 05/13/2009 - 15:09

Hi Przemek,

Great question. This feature is not documented. I had to request this information from Engineering. I will let the docs group know to update next time they revise the ATA admin guide.

Voice tab > Line N tab > Audio Configuration > FAX T38 Redundancy:

The number corresponds to how many previous packet payloads are repeated with each packet.  Zero means no payload redundancy.  Default is 1 (which matches previous behavior, that is we have been using redundancy = 1 all along).  The higher the number, the larger the packet size and hence the larger the bandwidth consumed.  This is independent of packet rate.

The Admin Guide describes configuring T.38 faxing in detail on page 55 in the Using a Fax Machine section.

Available from: https://www.myciscocommunity.com/docs/DOC-2149

Direct link: http://www.cisco.com/en/US/docs/voice_ip_comm/csbpvga/ata/administration/guide/ATA_AG_v3_NC-WEB.pdf

Regards,

Patrick

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przemyslawsiwek Thu, 05/14/2009 - 04:16

Thank you for your answer.

I have one more quetions. Does WRP400 support t38?

In GUI of WRP400 i found setting for T.38, but in documentation is "T.38 Fax is only supported on the SPA2102, SPA3102, and the SPA8000. The SPA2102 and SPA3102 support a single connection, while the SPA8000 supports one connection for each pair of ports (1/2, 3/4, 5/6, and 7/8) for a maximum of four connections."

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