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U1981 to Lync call failed. SIP 488 Invalid incoming Gateway SDP Invalid media

Publication Date:  2016-11-10 Views:  6013 Downloads:  0

Issue Description

U1981 SW version - V200R003C20SPC500B013

MS Lync 2013 server

Calls from MS Lync to U1981 transmit properly.

Calls from PSTN to Lync failed.

Alarm Information

Calls from PSTN to Lync failed. Error appeared: SIP/2.0 488 Invalid incoming Gateway SDP: Invalid media


Handling Process

Check INVITE message towards Lync:

IsCallMsg:[Y], Direction:[10.1.X.X--->10.6.X.X]
INVITE sip:495XXXXXXX@10.6.X.X:5068;transport=tcp;user=phone SIP/2.0
Via: SIP/2.0/TCP 10.1.X.X:5068;branch=z9hG4bKifucfjmf9cehjgrejkcbbhcgh;rport
Call-ID: bcullcfacmlhcal9bhlahlmeglufruag@10.1.X.X
From: <sip:495XXXXXXX@10.1.X.X:5068;transport=tcp;user=phone>;tag=j3ljigaf
To: 495XXXXXXX <sip:495XXXXXXX@10.6.X.X:5068;transport=tcp;user=phone>
Contact: <sip:495XXXXXXX@10.1.X.X:5068;transport=tcp;user=phone>
Supported: 100rel
Max-Forwards: 70
Content-Length: 721
Content-Type: application/sdp

o=HuaweieSpaceV200R003C20SPC500 3546 3546 IN IP4 10.1.X.X
s=Sip Call
c=IN IP4 10.1.X.X
t=0 0
m=audio 13984 RTP/AVP 8 0 18 4 98 102 9 103 104 105 101
a=rtpmap:8 PCMA/8000
a=rtpmap:0 PCMU/8000
a=rtpmap:18 G729/8000
a=rtpmap:4 G723/8000
a=rtpmap:98 iLBC/8000
a=rtpmap:102 iLBC/8000
a=rtpmap:9 G722/8000
a=rtpmap:103 G7221/16000
a=rtpmap:104 G7221/16000
a=rtpmap:105 AMR-WB/16000
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-15
a=fmtp:18 annexb=no
a=fmtp:4 annexa=no
a=fmtp:102 mode=30
a=fmtp:98 mode=20
a=fmtp:104 bitrate=32000
a=fmtp:103 bitrate=24000
a=fmtp:105 mode-set=0,1,2,3,4,5,6,7,8

Root Cause

Customer’s MS Lync server supports only G711A and G711U audio codecs. Lync rejected incoming calls with audio codecs, which are not supported.


Exclude all audio codecs U1981 support except G711A and G711U for the call.

Configure U1981 SIP-trunk to Lync with allow only G711A and G711U audio codecs support:

Configure IP-phone with G711A and G711U codecs support only:

In my case call still failed. Audio coedec settings for SIP-trunk to Lync is not enough to resolve the issue. INVITE packet still contain not allowed by Lync audio codecs after transmitting through MD-110 PRA-trunk.

Audio codecs restriction should be configured on U1981 to apply codec restriction for PRA-trunk too:

config system codetype g711a&g711u

Setting above wasn’t applied to U1981 successfully. This is a bug of V200R003C20SPC500 software version. Upgrade U1981 with patches from version V200R003C20SPC500 to version V200R003C20SPH502 to resolve this issue.

Type the command again after successful patch installation:

config system codetype g711a&g711u

Check U1981 codec state:

Try the call again.

Now INVITE message contains following information:

o=HuaweieSpaceV200R003C20SPC500 4002 4002 IN IP4 10.1.X.X
s=Sip Call
c=IN IP4 10.1.X.X
t=0 0
m=audio 11664 RTP/AVP 8 0 101
a=rtpmap:8 PCMA/8000
a=rtpmap:0 PCMU/8000
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-15

Lync doesn’t complain on Media. It means U1981 negotiate audio codecs with Lync properly.