Reliably Transmitting (no NAT) to 63.209.144.201:5060:
INVITE sip:00543515544154@sip.skype.com SIP/2.0
Via: SIP/2.0/UDP 190.220.135.170:5060;branch=z9hG4bK1e044cc6;rport
Max-Forwards: 70
From: "bui142" <sip:99051000141672@sip.skype.com>;tag=as582a2ff3
To: <sip:00543515544154@sip.skype.com>
Contact: <sip:99051000141672@190.220.135.170>
Call-ID: 2791b0b3110596da55b6f5972dea9cfb@sip.skype.com
CSeq: 102 INVITE
User-Agent: Asterisk PBX 1.6.2.18
Date: Fri, 15 Jul 2011 21:27:21 GMT
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY, INFO
Supported: replaces
Content-Type: application/sdp
Content-Length: 266

v=0
o=root 1753181732 1753181732 IN IP4 190.220.135.170
s=Asterisk PBX 1.6.2.18
c=IN IP4 190.220.135.170
t=0 0
m=audio 16736 RTP/AVP 18 101
a=rtpmap:18 G729/8000
a=fmtp:18 annexb=no
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-16
a=ptime:20
a=sendrecv

---
    -- Called sipTrunkSkypeBui/00543515544154

<--- SIP read from UDP:63.209.144.201:5060 --->
SIP/2.0 100 Trying
From: "bui142" <sip:99051000141672@sip.skype.com>;tag=as582a2ff3
To: <sip:00543515544154@sip.skype.com>
Call-ID: 2791b0b3110596da55b6f5972dea9cfb@sip.skype.com
CSeq: 102 INVITE
Via: SIP/2.0/UDP 190.220.135.170:5060;branch=z9hG4bK1e044cc6;rport=5060
Contact: <sip:00543515544154@sip.skype.com:5060;maddr=63.209.144.201;transport=udp>
Content-Length: 0


<------------->
--- (8 headers 0 lines) ---

<--- SIP read from UDP:63.209.144.201:5060 --->
SIP/2.0 407 Proxy Authentication Required
From: "bui142" <sip:99051000141672@sip.skype.com>;tag=as582a2ff3
To: <sip:00543515544154@sip.skype.com>;tag=ca90d13f-13c4-4e20b0b9-2e7b5848-1b7a213
Call-ID: 2791b0b3110596da55b6f5972dea9cfb@sip.skype.com
CSeq: 102 INVITE
Proxy-Authenticate: Digest realm="sip.skype.com", nonce="4e20b0d700002010b4e714ddb1f038b4b692dd040d9fb3ac", algorithm=MD5
Via: SIP/2.0/UDP 190.220.135.170:5060;branch=z9hG4bK1e044cc6;rport=5060
Content-Length: 0


<------------->
--- (8 headers 0 lines) ---
Transmitting (no NAT) to 63.209.144.201:5060:
ACK sip:00543515544154@sip.skype.com SIP/2.0
Via: SIP/2.0/UDP 190.220.135.170:5060;branch=z9hG4bK1e044cc6;rport
Max-Forwards: 70
From: "bui142" <sip:99051000141672@sip.skype.com>;tag=as582a2ff3
To: <sip:00543515544154@sip.skype.com>;tag=ca90d13f-13c4-4e20b0b9-2e7b5848-1b7a213
Contact: <sip:99051000141672@190.220.135.170>
Call-ID: 2791b0b3110596da55b6f5972dea9cfb@sip.skype.com
CSeq: 102 ACK
User-Agent: Asterisk PBX 1.6.2.18
Content-Length: 0