Information Technology Reference
In-Depth Information
This command ensures that the gateway treats the incoming (ISDN) Alerting message as if it contains a progress indicator of
8, which indicates that in-band information is available. (The PSTN does not actually include this progress indicator in the
Alerting message in this situation [PI=0].)
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No ringback tone on a phone in the PSTN when calling an IP phone:
This occurs because the IOS gateway does not play
a ringback tone to the phone on the PSTN because the Setup message received from the PSTN did not include a progress
indicator (PI=0).
The gateway assumes the network is ISDN end to end and that playback tones will be handled by the PSTN, but in fact, that
network is not ISDN end to end, and tones are therefore not handled by the PSTN. (The PSTN should have sent the Setup
message with a progress indicator of 3.)
This issue can be resolved by configuring the
progress_ind setup enable 3
command under VoIP dial peers that are used for
the incoming call. This command forces the gateway to play an in-band ringback tone irrespective of the progress indicator in
the Setup message.
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No ringback tone is played to the phone on the PSTN when a call is transferred by an IP phone:
This issue is caused
because an IOS gateway tears down logical channels when transferring a call, so audio is not sent.
This issue can be solved by running IOS 12.2(3) and later, together with CUCM 3.0(8) and later, and setting the CUCM
ToSendH225UserInfoMsg service parameter to True.
IOS H.323 gateways can send DTMF digits in a number of ways, including the following:
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H.245 alphanumeric:
In this case, digit tones are sent out-of-band via H.245 signaling, but this does not include tone
duration. (Each digit is assumed to be 500 ms long.)
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H.245 signal:
This is similar to H.245 alphanumeric, but tone duration is sent.
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RTP-NTE:
Tones are sent in the RTP stream using NTE packets, with the payload type value being negotiated.
■
Cisco proprietary:
Tones are sent in the RTP stream using payload type 121.
