asterisk users - Mar 2005 - help understanding sip header

What are these messages that * constantly sends to the client?  And
why does it always say 'looking for [server ip] in default'  ?

Sometimes I see 404's instead of 200's, and I know something is wrong
but I don't know what is being signalled here.

In this case 206.80.111.117 is the * server,  and 4.27.217.38 is my nat box.


<-- SIP read from 4.27.217.38:61384: 
OPTIONS sip:206.80.111.117 SIP/2.0
Content-Length: 0
Call-ID: 5F620712-81EE-4E77-925D-DCF4697C129E@192.168.0.30
From: <sip:chris@206.80.111.117>;tag=22240583790
CSeq: 7 OPTIONS
Max-Forwards: 70
To: <sip:206.80.111.117>
Via: SIP/2.0/UDP
192.168.0.30;rport;branch=z9hG4bKc0a8001e0131c9b1424260a4000012c800000019


--- (8 headers 0 lines)---
Looking for 206.80.111.117 in default
Transmitting (no NAT) to 4.27.217.38:61384:
SIP/2.0 200 OK
Via: SIP/2.0/UDP
192.168.0.30;branch=z9hG4bKc0a8001e0131c9b1424260a4000012c800000019
From: <sip:chris@206.80.111.117>;tag=22240583790
To: <sip:206.80.111.117>;tag=as298650c3
Call-ID: 5F620712-81EE-4E77-925D-DCF4697C129E@192.168.0.30
CSeq: 7 OPTIONS
User-Agent: Asterisk PBX
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER
Contact: <sip:206.80.111.117>
Accept: application/sdp
Content-Length: 0


---
Destroying call '5F620712-81EE-4E77-925D-DCF4697C129E@192.168.0.30'

These OPTIONs packets are what we send for qualification, a scheme that 
can also be used for NAT keepalives. You turn them on by adding 
"qualify=yes" in the [peer] section of sip.conf

With qualification on, we regurlarly measure the latency between
Asterisk and the client and decide whether the client is reachable or not.

Sometimes these generate odd answers, like 404 Not Found. Do not worry, 
it doesn't mean anything. It's not very beautiful but it happens.

/Olle