Hi,
I set up the following scenario: 20 callers on different machines make
continuous calls to one single SIP server. The callers and server use
default configuration files.
I then use tcpdump to capture packets on the SIP server, and find that about
10% of all SIP messages are "200 OK" sent by the server to WRONG callers.
Here "WRONG" means that the "200 OK" message follows an early INVITE from
caller A, but tcpdump shows that the "200 OK" is actually destined to caller
B.
For example, the following is a packet captured by tcpdump. The TCP/IP
header shows that this message is sent to 128.112.139.96 by SIP server
(128.112.139.78), but if you look at the "From." and "To." fields in SIP
message portion, you will find that this is a "200 OK" message destined for
136.145.115.196.
1174505710.070239 IP (tos 0x0, ttl 64, id 787, offset 0, flags [DF], proto:
UDP (17), length: 517) 128.112.139.78.5060 > 128.112.139.96.5060: SIP,
length: 489
SIP/2.0 200 OK
Via: SIP/2.0/UDP 136.145.115.196:5060;branch=z9hG4bK-8788-28-0
From: sipp <sip:[EMAIL PROTECTED]:5060>;tag=28
To: sut <sip:[EMAIL PROTECTED]:5060>;tag=4565SIPpTag01328
Call-ID: [EMAIL PROTECTED]
CSeq: 1 INVITE
Contact: <sip:128.112.139.78:5060;transport=UDP>
Content-Type: application/sdp
Content-Length: 139
v=0
o=user1 53655765 2353687637 IN IP4 128.112.139.78
s=-
c=IN IP4 128.112.139.78
t=0 0
m=audio 6000 RTP/AVP 0
a=rtpmap:0 PCMU/8000
I'm puzzled by this issue for a few days. Could anybody give me some help?
Thanks a lot
-George
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