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Troubleshooting IP Solutions 2 H.323 Trunks
Administration for Network Connectivity
CID: 77730 555-233-504 — Issue 1 — April 2000
52
IP Softphone Problem Solving
Codecs used with
Netmeeting
Voice quality for the road-warrior application of DEFINITY IP softphone will vary
depending on several factors. Poor voice quality can be caused by the use of the
high-compression codecs (G.723 or G.729) in situations where the low-compression
codec (G.711) should be used. This can happen unexpectedly when using NetMeeting
— when the G.711 is set as the preferred codec on the switch, NetMeeting may fail to
use it. Since there is no way to monitor which codec is being used, the only way to
determine that this is the problem is to disable all but the G.711 codecs. Then, if calls
no longer work, it can be concluded that NetMeeting is failing to use the G.711. The
solution to this problem is to reinstall NetMeeting.
Telecommuter use of
phone lines
The telecommuter application of the IP Softphone requires the use of two phone lines:
one for the IP connection to DEFINITY, which is used for softphone registration and
call signaling, and the other for a PSTN connection, which DEFINITY uses as a
callback number to establish the voice path. How you allocate your phone lines to
these two functions may make a difference.
For example, assume that you have telephone services provided by the local phone
company, such as voice mail, associated with one of your lines and not the other. In
this case, you should use the line with the services to make the initial IP connection to
register the softphone and use the line without the services as the POTS callback for
the voice path. Otherwise, there could be undesirable interactions between the
softphone and the local services. For example, if your telecommuter application is
registered and you were using your POTS callback line for a personal call when a
business associate dialed your work extension, the business associate would hear your
home voice mail message.
NetMeeting drops
unanswered calls
For calls made to a NetMeeting softphone, if the call is not answered or if coverage is
not administered, after about 5 rings NetMeeting drops the call and the station stops
ringing but the caller continues to hear ringback. To avoid this situation, make sure
that coverage is administered for the NetMeeting softphone.
NetMeeting ignores
out-of-band tones
NetMeeting ignores any H.323 digits received out-of-band, so it never hears DTMF
from DEFINITY, which always strips DTMF from the audio path and plays it
out-of-band with H.323.
For example, if you are on a call on a NetMeeting softphone and the calling party
presses a number or character on their keypad, you will not hear the tone.