В составе плагина есть интересная утилита SIPTester.exe, которая тестирует устройства и sip cоединения.
Вот какой выводит результат по запросу sipnet.ru:
01.11.2011 1:44:14
[Status]
OK
[Request]
OPTIONS sip:212.53.40.40 SIP/2.0
Via: SIP/2.0/UDP 192.168.12.24:4878;branch=z9hG4bK-7f6e533f-c74e-477b-8960-757839ab5464
From: Anonymous ;tag=1928301774
To:
Call-ID: 89905e35-8778-4886-9ce0-f199ceb2f5aa
CSeq: 1 OPTIONS
Contact:
Max-Forwards: 70
Accept: application/sdp
Content-Length: 0
[Response]
SIP/2.0 200 OK
Via: SIP/2.0/UDP 192.168.12.24:4878;branch=z9hG4bK-7f6e533f-c74e-477b-8960-757839ab5464;received=165.112.20.50
From: "Anonymous" ;tag=1928301774
To: ;tag=5FE084C7
Call-ID: 89905e35-8778-4886-9ce0-f199ceb2f5aa
CSeq: 1 OPTIONS
Date: Mon, 31 Oct 2011 21:44:27 GMT
Allow: PUBLISH,SUBSCRIBE
Supported: path,gruu
Allow-Events: presence,message-summary,reg,dialog,line-seize,keep-alive,refer
Server: CommuniGatePro/5.4.2
Content-Length: 0