SIP send a lot of INVITE msg to Gateway?

Voice & Telephony
1

Hi all,

Pls help me clarify this problem. My topology as follows:
X-lite 10.56.237.75 (1004)===SIPsrv 10.56.237.32 ===Audiocodes Gateway 10.56.237.128 ===PSTN.

I call out to mobile number ‘0904716790’. It take 10s to customer receive that call. When i check sip flow in wireshark. I saw 4 INVITE sent from SIPsrv. And it take that time.

Here is flow i capture by wireshark.
http://www.upsieutoc.com/image/p28cHY

2

Always 10 seconds?

Your issue is on AudioCodes (or in the network between your SIP Server and AudioCodes dropping packets).

Note that it takes 5 INVITE messages for AudioCodes to respond with 100 Trying. That response should be immediate. Try enabling syslog on the AudioCodes to get more clue on why is it taking to long to respond.

Complementing:

By the SIP RFC 3261, Section 16.2 “Stateful Proxy”:


A stateful proxy creates a new server transaction for each new
request received. Any retransmissions of the request will then be
handled by that server transaction per Section 17. The proxy core
MUST behave as a UAS with respect to sending an immediate provisional
on that server transaction (such as 100 Trying) as described in
Section 8.2.6. Thus, a stateful proxy SHOULD NOT generate 100
(Trying) responses to non-INVITE requests.

3

If 10.56.237.128 is the audiocodes device the problem is on the PSTN side.

4

Thanks a lot hsujdik, genesysguru, I fixed that problem. That’s because GW take 10s to ask DNS server about domainname of VIP SIP Switch ;D