Dialogic 6.2 Manuale Utente

Managing Calls Using IP Telephony

November 2009

226

This Brooktrout SDK supports the H.323 protocol (version 4 and 

Annex D), providing end point functionality only. Our current H.323 

implementation does not operate as a gateway or H.323 Gatekeeper, 

but you can configure your application to communicate with a 

gateway or H.323 Gatekeeper.

The H.323 implementation supports both a primary and alternate 

H.323 Gatekeeper. When an application is configured to 

communicate with a Gatekeeper, all the RAS messages exchanged 

with the Gatekeeper are done inside of the H.323 implementation 

without requiring the application to get involved. The H.323 

implementation registers the end points transport address and alias 

information with the Gatekeeper and resolves destination alias 

addresses with the Gatekeeper. If the application turns on alternate 

Gatekeeper support and the primary Gatekeeper becomes 

unavailable, the H.323 implementation automatically falls back to 

an alternate Gatekeeper without involving the application.

Multiple Protocols

SIP and H.323 can co-exist in the same system. You can configure a 

single hardware module or SR140 module to support either SIP or 

H.323, selecting which protocol stack to use on a per-module basis. 

The protocols can operate simultaneously on different modules.

Different modules in the same system can support different IP call 

control stacks, but the SR140 Fax Software implementation only 

supports one IP stack at a time.

Supporting Media

The H.323 implementation supports T.38 (Fax Media) and RTP 

media over UDP (H.323 Annex D).

The H.323 implementation supports the ability to negotiate a pseudo 

G.711 media session with the intent of renegotiating to a T.38 media 

session even when RTP prompt playback/record capability is not 

desired.

This functionality is required to interoperate with certain supported 

equipment. Media renegotiation to T.38 is also supported after a call 

is setup.

The H.323 implementation supports basic call control functionality, 

specifically outbound call setup and teardown and inbound call 

detection, answering, and teardown. See the sections on 

 and 

 for information 

about the functions that support these activities.