Dialogic 05-2239-009 User Manual
54
Dialogic
®
Global Call IP Technology Guide — November 2007
Dialogic Corporation
IP Call Scenarios
Note that in some cases it is possible to enable streaming in one direction significantly earlier than
in the other direction. To take full advantage of this fact, the Global Call IP call control library
initially enables a temporary unidirectional connection, then modifies the connection to be full
duplex as soon as that is possible.
in the other direction. To take full advantage of this fact, the Global Call IP call control library
initially enables a temporary unidirectional connection, then modifies the connection to be full
duplex as soon as that is possible.
3.1.3.1
H.323 FastStart Mode
The library’s default for H.323 operation enables the Global Call FastStart mode, in which the
channel capability information is embedded in a fastStart element (indicated in the figure as
“FSE”) that can be sent within the messages of the H.225 Setup exchange rather than using the
H.245 messages. (This minimizes the number of round-trip message exchanges and avoids the
latency of H.245 channel establishment.) As a calling endpoint, the Dialogic
channel capability information is embedded in a fastStart element (indicated in the figure as
“FSE”) that can be sent within the messages of the H.225 Setup exchange rather than using the
H.245 messages. (This minimizes the number of round-trip message exchanges and avoids the
latency of H.245 channel establishment.) As a calling endpoint, the Dialogic
®
Global Call API
library enables media after Alerting is received if the called endpoint supports the fastStart mode.
As a called endpoint, the Global Call library enables media in a fastStart connection after the
application calls gc_AcceptCall( ).
As a called endpoint, the Global Call library enables media in a fastStart connection after the
application calls gc_AcceptCall( ).
If the calling endpoint sets the MediaWaitForConnect element in the Setup message, the Dialogic
®
Global Call API library does not enable media transmission for a called endpoint until the Connect
message is sent.
message is sent.
Figure 10. H.323 Early Media, FastStart Mode
gc_MakeCall( )
Calling
App
Called
App
IP
CCLib
IP
CCLib
GCEV_ALERTING
GCEV_CONNECTED
GCEV_EXTENSION
(EXTID_MEDIAINFO - RX)
GCEV_EXTENSION
(EXTID_MEDIAINFO - TX)
GCEV_EXTENSION
(EXTID_MEDIAINFO - RX)
GCEV_EXTENSION
(EXTID_MEDIAINFO - TX)
GCEV_DETECTED/OFFERED
GCEV_ANSWERED
GCEV_ACCEPT
gc_AcceptCall( )
gc_AnswerCall( )
FACILITY(TCS, MSD)
FACILITY(TCS, MSD,
TCSAck, MSDAck)
FACILITY(TCSAck, MSDAck)
SETUP(fse OLC , OLC ,
OLC , OLC , ...)
Fm
Fn
Rn
Rm
PROGRESS(fse with OLC
and OLC )
Ry
Fx
CONNECT(fse with OLC
and OLC )
Ry
Fx
ALERTING(fse with OLC
and OLC )
Ry
Fx
Unidirectional media
streams are enabled
after the ALERTING
is received and before
each respective
GCEV_EXTENSION
(MEDIAINFO) event
is dispatched.
streams are enabled
after the ALERTING
is received and before
each respective
GCEV_EXTENSION
(MEDIAINFO) event
is dispatched.
Unidirectional media
streams are enabled
before each respective
GCEV_EXTENSION
(MEDIAINFO) event
is dispatched and
before the ALERTING
response is sent.
streams are enabled
before each respective
GCEV_EXTENSION
(MEDIAINFO) event
is dispatched and
before the ALERTING
response is sent.
Pre condition:
Both line devices are IDLE. Called party has executed gc_WaitCall().
FastStart is enabled. Tunneling is enabled.
Post condition: Call is connected.