#
U 8XX.XXX.X96:1879 -> 2XX.XXX.XXX.X8:5060
INVITE sip:0123456789@sipserver.xy.mydomain.org;user=phone SIP/2.0.
Via: SIP/2.0/UDP 10.1.99.161:5060;branch=z9hG4bKd1d8154c1C0FA1C7.
From: "Test2" <sip:666555804@sipserver.xy.mydomain.org>;tag=D4463162-BBC51ECB.
To: <sip:0123456789@sipserver.xy.mydomain.org;user=phone>.
CSeq: 1 INVITE.
Call-ID: 12f4a0ce-6b2a600-d177cb11@10.1.99.161.
Contact: <sip:666555804@10.1.99.161:5060>.
Allow: INVITE, ACK, BYE, CANCEL, OPTIONS, INFO, MESSAGE, SUBSCRIBE, NOTIFY, PRACK, UPDATE, REFER.
User-Agent: PolycomSoundPointIP-SPIP_501-UA/1.6.7.0098.
Supported: 100rel,replaces.
Allow-Events: talk,hold,conference.
Max-Forwards: 70.
Content-Type: application/sdp.
Content-Length: 247.
.
v=0.
o=- 1159352772 1159352772 IN IP4 10.1.99.161.
s=Polycom IP Phone.
c=IN IP4 10.1.99.161.
t=0 0.
a=sendrecv.
m=audio 2236 RTP/AVP 0 8 18 101.
a=rtpmap:0 PCMU/8000.
a=rtpmap:8 PCMA/8000.
a=rtpmap:18 G729/8000.
a=rtpmap:101 telephone-event/8000.

#
U 2XX.XXX.XXX.X8:5060 -> 8XX.XXX.X96:5060
SIP/2.0 407 Proxy Authentication Required.
Via: SIP/2.0/UDP 10.1.99.161:5060;branch=z9hG4bKd1d8154c1C0FA1C7;received=8XX.XXX.X96.
From: "Test2" <sip:666555804@sipserver.xy.mydomain.org>;tag=D4463162-BBC51ECB.
To: <sip:0123456789@sipserver.xy.mydomain.org;user=phone>;tag=2f7d8fa65b1e4a32386804888f034ca8.b3bf.
CSeq: 1 INVITE.
Call-ID: 12f4a0ce-6b2a600-d177cb11@10.1.99.161.
Proxy-Authenticate: Digest realm="sipserver.xy.mydomain.org", nonce="451a9b18ed7ecc6616af7ad9d07a019e47075c4c".
Server: OpenSer (1.1.0-tls (i386/linux)).
Content-Length: 0.
Warning: 392 2XX.XXX.XXX.X8:5060 "Noisy feedback tells:  pid=12123 req_src_ip=8XX.XXX.X96 req_src_port=1879 in_uri=sip:0123456789@sipserver.xy.mydomain.org;user=phone out_uri=sip:0123456789@sipserver.xy.mydomain.org;user=phone via_cnt==1".
.