Incoming Call Failed Due to Duplicate URI in P-Asserted-ID in the INVITE Message

Hello, everyone!

Today, I'd like to share a case with you.

Problem Description

if configure display name from Softswitch, incoming call failed with 400 bad messages, after remove the display name in Softswitch, everything works fine network topology as bellow.

Handling Procedure

Step 1: Check current configuration, confirm configuration no problem.

Step 2: Capture the signaling logs, trace signaling find any fault in the messages from MDU can use open dbwin to trace the signaling logs :

• Open dbwin to trace the signaling
    MA5620E_B(su)%%
    MA5620E(config)#diagnose
    MA5620E(diagnose)%%su                                               
    MA5620E(su)%in enable
    MA5620E(su)%in print 0x9d 1 1
    MA5620E(su)%in send 0x9d 1 1

• Reappear this issue, you will see the signaling print out, please feedback the signaling trace log. after log collection, close the dbwin.

       MA5620E(su)%in print 0x9d 1 0
       MA5620E(su)%in send 0x9d 1 0
       MA5620E(su)%in disable

Root Cause

1. Analysis of the SIP signaling of the incoming call, we found that the MA5620 reply an error message (SIP/2.0 400 Bad Request) when received the INVITE message. There is a warning in the reply that is “Warning: 399 10.33.101.187 "SS150000F150L1936[05406] P-Asserted-ID usage error":
   

   
   

2. Then we checked the P-Asserted-ID in the INVITE message and found that there were two same URI(<sip:3640@10.33.30.2>) in the P-Asserted-Identity header, this is why MA5620 reply 400 Bad Request to the INVITE message:

   

   
   

3. MA5620 does this checking base on this description in the RFC3325. If there are two values, one value MUST be a sip or sips URI and the other MUST be a tel URI:

   

Solution

1.suggest removing the duplicate URI from Softswitch

2.Some new versions optimize it according to RFC 5876, to ignore the duplicate URI.

Summary and Suggestion 

1.trace the signaling is the common method when we do VOIP troubleshooting;

2.suggest customers when configuring VOIP service in Softswitch according to the standard and consider old device can support it.

3.reference RFC document :

http://www.ietf.org/rfc/rfc3325.txt

http://www.ietf.org/rfc/rfc5876.txt

Thanks.