Snom 7xx series codec issue with Exchange 2010 UM

Hi, during a Lync 2013 installation, with Exchange UM integration and snom deployment, I’ve found an issue with snom 7xx phone series and Exchange 2010 UM services.

With the default snom 720 configuration, the IP phone cannot access the Exchange Voicemail (Subscriber Access) and Exchange AutoAttendant, the SIP signaling was ok, not the media communication.

Exchange 2010 server is updated at SP1 RU8 level.
There is no issue if I use a snom 821.

If you look at SIP Trace from snom 821 when you call Exchange Subscriber Access Service, you can find

 m=audio 55926 RTP/AVP 9 0 8 99 18 101
 a=rtpmap:9 G722/8000
 a=rtpmap:0 PCMU/8000
 a=rtpmap:8 PCMA/8000
 a=rtpmap:99 G726-32/8000
 a=rtpmap:18 G729/8000
 a=fmtp:18 annexb=no
 a=rtpmap:101 telephone-event/8000

the same SIP Trace from snom 720

m=audio 57818 RTP/AVP 9 0 8 115 3 97 98 99 100 18 101
 a=rtpmap:9 G722/8000
 a=rtpmap:0 PCMU/8000
 a=rtpmap:8 PCMA/8000
 a=rtpmap:115 x-msrta/8000
 a=fmtp:115 bitrate=11800
 a=rtpmap:3 GSM/8000
 a=rtpmap:97 G726-16/8000
 a=rtpmap:98 G726-24/8000
 a=rtpmap:99 G726-32/8000
 a=rtpmap:100 G726-40/8000
 a=rtpmap:18 G729/8000
 a=fmtp:18 annexb=no
 a=rtpmap:101 telephone-event/8000

The problem seems to be represented by an audio codec incompatibility between snom 7xx and Exchange 2010 SP1 UM Service.

The workaround I’ve found is to change the snom audio codec configuration.
I’ve tested the snom 821 codec order with success: g722,pcmu,pcma,g726-32,g729,telephone-event

You can use snom provisioning file to change your snom phone deployment, simply add these line to your snom7xx.htm configuration file.

<codec_priority_list idx=”1″ perm=””>g722,pcmu,pcma,g726-32,g729,telephone-event</codec_priority_list>
<codec_priority_list idx=”2″ perm=””>g722,pcmu,pcma,g726-32,g729,telephone-event</codec_priority_list>
<codec_priority_list idx=”3″ perm=””>g722,pcmu,pcma,g726-32,g729,telephone-event</codec_priority_list>
<codec_priority_list idx=”4″ perm=””>g722,pcmu,pcma,g726-32,g729,telephone-event</codec_priority_list>
<codec_priority_list idx=”5″ perm=””>g722,pcmu,pcma,g726-32,g729,telephone-event</codec_priority_list>
<codec_priority_list idx=”6″ perm=””>g722,pcmu,pcma,g726-32,g729,telephone-event</codec_priority_list>
<codec_priority_list idx=”7″ perm=””>g722,pcmu,pcma,g726-32,g729,telephone-event</codec_priority_list>
<codec_priority_list idx=”8″ perm=””>g722,pcmu,pcma,g726-32,g729,telephone-event</codec_priority_list>
<codec_priority_list idx=”9″ perm=””>g722,pcmu,pcma,g726-32,g729,telephone-event</codec_priority_list>
<codec_priority_list idx=”10″ perm=””>g722,pcmu,pcma,g726-32,g729,telephone-event</codec_priority_list>
<codec_priority_list idx=”11″ perm=””>g722,pcmu,pcma,g726-32,g729,telephone-event</codec_priority_list>
<codec_priority_list idx=”12″ perm=””>g722,pcmu,pcma,g726-32,g729,telephone-event</codec_priority_list>

You can find more information on codec priority at snom Wiki page http://wiki.snom.com/Settings/codec_priority_list

I hope this could help.
Bye,
Luca

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