Advantech MIC-3369C Installationsanleitung PDF herunterladen (Seite 52)

Dialogic

System Release 6.1 CompactPCI for Windows

Release Update 52

With the Service Update, the ability to disable/enable the sending of the automatic SIP re-

INVITE message upon media switch can now be configured with the Dialogic

Global Call

API to prevent this glare condition.

1.14.1 Feature Description

Overview of Use Case

A user application can enable and disable the unsolicited GCEV_EXTENSION notification

events associated with certain types of transition events, including media streaming

connection state changes. The application can receive notification of changes in the

status (connection and disconnection) of media streaming in the transmit and receive

directions as GC_EXTENSIONEVT events. The events for this notification must be

enabled by setting or adding the bitmask value EXTENSIONEVT_SIGNALING_STATUS

to the GC_EXTENSIONEVT mask. Events can be enabled on a per board basis (using

gc_SetConfigData( )) or on a per channel basis (using gc_SetUserInfo( )).

A user application needs to enable media streaming status

EXTENSIONEVT_STREAMING_STATUS to get notification of media transmit and

receive connected events before doing specific media tests just after another media test is

completed. This is particularly useful in back-to-back testing, because in live applications

there are other indications of media session events, e.g., fax CNG/CED tones, busy tone,

phone hang-up tone, etc., which are not available in back-to-back testing.

For example, consider two user applications where one makes an IP call to the other,

sends a fax (over IP), and after the fax session is completed, dials a string of DTMF digits

for the other side to detect. If the DTMF digits are dialed before the fax session completely

ends, the DTMF dial test will fail, since the media session has not switched from fax to

audio yet. In order for the application to know when to dial the DTMF digits it has to know

when the previous fax session has ended and the audio session has started. It knows this

when it receives an event indicating that the audio media stream is connected.

When working with the H.323 protocol, this functionality to detect the media switch is

sufficient for user applications. However for SIP protocols, when a fax to audio switch

occurs, both sides send a re-INVITE message to renegotiate the media session between

them, which causes a glare condition that drops the call. This is not an expected situation

for a user application.

A similar situation can occur when the media switches from audio to fax.

New Parameters to Disable/Enable Automatic re-INVITE Messages

In order to prevent this glare situation, new parameters are now available in Global Call to:

• prevent sending an automatic SIP re-INVITE when a switch from fax to audio media

occurs, or when a switch from audio to fax media occurs

• re-enable the sending of an automatic SIP re-INVITE when a switch from fax to audio

media occurs, or when a switch from audio to fax media occurs

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Advantech MIC-3369C Installationsanleitung Seite 52