CALL ESTABLISHMENT PROCEDURES FOR T.38 H.248/MEGACO MEDIA GATEWAYS
CAPABLE OF AUTONOMOUS TRANSITION BETWEEN VoIP AND T.38 FoIP
Nortel Networks
This document describes MEGACO/H.248 [6,2] call-setup set up procedures that enable T.38 [4] capable media gateways to transition between a Voice over IP (VoIP) call and a Facsimile over IP (FoIP) (using ITU-T Rec. T.38) call either: a) with the real-time intervention of a Media Gateway Controller (MGC) using one of the existing mechanisms in Rec. T.38 Annex B/H.323, Rec. T.38 Annex D/SIP-SDP and Rec. T.38 Annex E/H.248, and Rec. H.323 Annex D. b) without the real-time intervention of a Media Gateway Controller (MGC). The only involvement of the MGC will be during initial connection capabilities negotiation between the media gateways. At this stage, both the MGs and the MGCs are unaware of the type of connection, (i.e. Voice, Fax, Modem, etc.). This contribution also describes how these call set-up procedures can be used in conjunction with the existing procedures of ITU-T Rec. H.323 Annex D to set-up two parallel channels, one for voice and the other for T.38, without any modifications of the procedures.