[sip-comm-issues] [Issue 832] New - SIP Message Processing Delay in Isolated network without DNS server

girish_k at dev.java.net girish_k at dev.java.net
Fri Jun 25 09:29:21 CEST 2010

                 Issue #|832
                 Summary|SIP Message Processing Delay in Isolated network witho
                        |ut DNS server 
              OS/Version|Windows Vista
       Status whiteboard|
              Issue type|DEFECT
             Assigned to|issues at sip-communicator
             Reported by|girish_k

------- Additional comments from girish_k at dev.java.net Fri Jun 25 07:29:15 +0000 2010 -------
We are using SIP Communicator(Version-sip-communicator-src-1.0-alpha3-
nightly.build.2164) with a locally installed SIP server in our Intranet and it 
works perfectly fine for Third-party Call Control scenario orchestrated by a 
Application Server.

However, when we perform the same setup in a isolated Lab network with no DNS 
server and using Statically configured IPs on SIP server and Client machines, 
we are intermittently facing a strange behavior with Sip Communicator. It 
generates a 100 Trying message immediately on incoming INVITE, but notifies 
user of incoming call (as well as generates 180 Ringing) only after a long 
delay of 6-10 seconds. Also once user accepts the call (for which 200 OK is 
generated instantaneously), the ringing continues for many-many seconds because 
the Ack sent back by SIP server is not processed right away.

We have removed the DNS Server entries from IP settings of Network Adapter on 
Client machine and left both Primary/Secondary DNS servers blank.

We are not able to understand the reason for such a behavior. Noticed that Sip 
Server is sending Notify of Sip-Message-Summary to Sip Communicator after 
initial REGISTER which seems to be forcing Sip Communicator to send out 
multiple DNS SRV queries for _sip._udp.<ip-address>. Can this be hogging the 
threads of Sip Communicator and reason for the delay? Also, as we are using 
just IP Address in isolated Lab network; why is DNS lookup done at all?

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