[Serusers] Another Looping Question

[Java Rockx]

Hi All.

Below is a snippet of an INVITE and you can see the usual "trying - your 
call is important to us" in the dialog. Anyhow, for some reason SER 
occasionally attempts to sent the ACK to itself, which causes a looping 
condition. The last ACK shown is the start of the looping condition.

It only happens on occasion. SER should have consumed the ACK rather than 
attempted to forward it.

Can anyone explain this?

Regards,
Paul

IP Legend
-------------------
10.3.0.221 <http://10.3.0.221> - SER (behind a Cisco 3600 so ALG rewrote the 
IPs)
69.36.46.178 <http://69.36.46.178> - NATed SIP UA

U 2005/04/15 02:19:16.252614 69.35.46.178:5060 <http://69.35.46.178:5060> -> 
10.3.0.221:5060 <http://10.3.0.221:5060>
INVITE sip:8187768080 at sipdev.mycompany.net SIP/2.0.
Via: SIP/2.0/UDP 192.168.1.102:5060 <http://192.168.1.102:5060>
;branch=z9hG4bK3915905414.
From: Test User <sip:3215591439 at sipdev.mycompany.net>;tag=1465261089.
To: <sip:8187768080 at sipdev.mycompany.net>.
Call-ID: 2671219156 at 192.168.1.102.
CSeq: 101 INVITE.
Contact: <sip:3215591439 at 192.168.1.102:5060>.
Proxy-Authorization: Digest username="3215591439", realm="
sipdev.mycompany.net <http://sipdev.mycompany.net>", 
nonce="425f5e0de25efdb3f5a6125dcf2147bf30fe9177", uri="
sip:8187768080 at sipdev.mycompany.net", 
response="61996c3bdc10990fec7e245751777516", algorithm=MD5, 
cnonce="ae02e47a3355bada49ce344c92f48587", qop=auth, nc=00000002. 
max-forwards: 70.
Allow: INVITE, ACK, CANCEL, BYE, REFER, NOTIFY.
Content-Type: application/sdp.
Content-Length: 180.
.
v=0.
o=- 32014 3005 IN IP4 192.168.1.102 <http://192.168.1.102>.
s=-.
c=IN IP4 192.168.1.102 <http://192.168.1.102>.
t=0 0.
m=audio 13456 RTP/AVP 18 0 8 2 4 101.
a=rtpmap:101 telephone-event/8000.
a=fmtp:101 0-15.
a=ptime:20.
.

#
U 2005/04/15 02:19:16.276216 10.3.0.221:5060 <http://10.3.0.221:5060> -> 
69.35.46.178:5060 <http://69.35.46.178:5060>
SIP/2.0 100 trying -- your call is important to us.
Via: SIP/2.0/UDP 192.168.1.102:5060 <http://192.168.1.102:5060>
;branch=z9hG4bK3915905414;rport=5060;received=69.35.46.178<http://69.35.46.178>
.
From: Test User <sip:3215591439 at sipdev.mycompany.net>;tag=1465261089.
To: <sip:8187768080 at sipdev.mycompany.net>.
Call-ID: 2671219156 at 192.168.1.102.
CSeq: 101 INVITE.
Content-Length: 0.
.

#
U 2005/04/15 02:19:16.792795 69.35.46.178:5060 <http://69.35.46.178:5060> -> 
10.3.0.221:5060 <http://10.3.0.221:5060>
ACK sip:8187768080 at sipdev.mycompany.net SIP/2.0.
Via: SIP/2.0/UDP 192.168.1.102:5060 <http://192.168.1.102:5060>
;branch=z9hG4bK3499714875.
From: Test User <sip:3215591439 at sipdev.mycompany.net>;tag=1465261089.
To: <sip:8187768080 at sipdev.mycompany.net>;tag=
cdbfe46960d7566fcbe09f199f2b328d.c2bb.
Call-ID: 2671219156 at 192.168.1.102.
CSeq: 100 ACK.
Content-Length: 0.
.

#
U 2005/04/15 02:19:16.912146 10.3.0.221:5060 <http://10.3.0.221:5060> -> 
10.3.0.221:5060 <http://10.3.0.221:5060>
ACK sip:8187768080 at sipdev.mycompany.net SIP/2.0.
Max-Forwards: 10.
Record-Route: <sip:10.3.0.221 <http://10.3.0.221>;ftag=1465261089;lr>.
Via: SIP/2.0/UDP 10.3.0.221 <http://10.3.0.221>;branch=0.
Via: SIP/2.0/UDP 192.168.1.102:5060 <http://192.168.1.102:5060>;received=
69.35.46.178 <http://69.35.46.178>;branch=z9hG4bK3499714875.
From: Test User <sip:3215591439 at sipdev.mycompany.net>;tag=1465261089.
To: <sip:8187768080 at sipdev.mycompany.net>;tag=
cdbfe46960d7566fcbe09f199f2b328d.c2bb.
Call-ID: 2671219156 at 192.168.1.102.
CSeq: 100 ACK.
Content-Length: 0.
P-hint: Local Destination.
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