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FAX passthrough over SIP (with protocol usage)

s.souroutis
Level 1
Level 1

<b>Our Scenario:

------------------- </b>

A fax located in a non-T.38 SIP VoIP network (non-Cisco) is calling a fax connected in a PABX connected to the SIP network via a 26XX PRI-VoIP Cisco router with IOS 12.3.(e.g. 3640 Cisco Router)

The call starts from the network with default compression codec (G.729), fax should be normally be detected by 26XX & change to G.711 should follow.

However it is required that 26XX informs via SIP signaling the SIP network for this change. Normally the SIP-network expects a re-Invite so that it adapts to the new SDP.

<b>Our Question:

------------------- </b>

If re-invite message is sent & with what SDP from the 26XX.

Also in the other way around i.e for Fax calls originating from PABX-26XX towards the SIP network : if Cisco 26XX will accept SIP re-invite so that to switch to G.711 pass-though via SIP signaling.

1 Reply 1

s.souroutis
Level 1
Level 1

We are interested in using cisco products with a non T.38 SIP voip network (non CISCO). In continuation to our former question:

Is it possible to show us where to find a document that describes the message flow for FAX pass-through method using the latest IOS (12.3?). The more technical details this documents contains, the best.

Please tell us also which from Cisco products support SIP fax pass-through .

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