I am trying to understand the order of fax protocol selection. For example, lets take a PSTN gateway that is MGCP enabled. Fax passthrough, T38 relay and Cisco fax relay are enabled. Which protocol will be used to negotiate with the far end device first(ATA, vg248 etc) ? Is there a particular order in which negotiation takes place ?
On the mgcp gateway the follwing commands are present.
mgcp modem passthrough codec g711ulaw
mgcp modem passthrough voip mode nse
ccm-manager fax protocol cisco (default)
no mgcp t38 fax inhibit (default)