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U1911 Interconnect with Skype Gateway

Publication Date:  2017-12-21 Views:  728 Downloads:  19

Issue Description

User fail to make a call from PSTN to Huawei eSpace U1911 via the PRA Circuit with the Interconnection of SIP trunk to the Skype Gateway and Skype Business User.

Network Topo

PSTN/4G--------PRA------->U1911----------SIP Trunk ------------>Skype Gateway-------->Skype User.

Version of the U1911 = V200R003C20

Error Message : SIP 488  Invalid incoming Gateway SDP

Alarm Information


Handling Process

Wireshark to Capture the Logs from the network


Fail call logs as below.


From the Wireshark Log, we found from the Message Body , the Media Attribute is from PCMA , PCMU, G.729, G.723, iLBC, G.7221, AMR and it might be not compatible with the Skype Gateway User.

The Payload type is 101 while U1911 get response of 255 Payload from the Skype Gateway. 

Successful Call logs:

User use the X-Lite and successful to make a call to Skype Gateway and the Skype Business User.

Modify the Payload type at U1911 to match Skype Business.

From the Wireshark Log, we found from the Message Body , the first Media format Attribute X-Lite using is G.711A ( Media Format G.711 PCMA )


1. show cdsp argu


This is to check if the RFC2833 Flag is enable . By default Value is 0

config cdsp rfc2833 switch on

2.)The Default Value of Payload for RFC2883 is 255

config cdsp payloadtype RFC2883 value 101


3.)config cdsp payloadtype libc_1520 value 255

config cdsp payloadtype libc_1333 value 255

4.) Add one Codec only in the System and try one by one. The first codec will be G.711A which is similar like X-Lite .

Reason is Skype Business not able to Analysis many coded at the same time. Their Strategy is select those common codec which is used commonly.

Command Line : config sys codetype G711A
Next Command Line : config sys codetype G711A&G.711U
Continue on to Add others Codec Command Line : config sys codetype G711A&G.711U&G.729