Incoming call problems

Hi All,

I have installed Asterisk on one of our server and SIP to SIP and SIP to PSTN calls are working fine. Now I want to take incoming calls at asterisk and for that I have defined in sip.conf as follows;
[192.168.0.161]
context=incoming
host=192.168.0.161
port=5061
type=friend
fromdomain=192.168.0.161

but still calls are not going through and let me paste asterisk debug log here

<------------->
— (13 headers 15 lines) —
Sending to 64.34.77.100 : 5061 (NAT)
Using INVITE request as basis request - 28038400e346a71080000002b3d7b2ed@64.34.77.100
localhost*CLI>
<— Reliably Transmitting (NAT) to 64.34.77.100:5061 —>
SIP/2.0 407 Proxy Authentication Required
Via: SIP/2.0/UDP 64.34.77.100:5061;branch=z9hG4bK-8652480-279398115-33554560-3987920819;received=64.34.77.100;rport=5061
From: “112” sip:1002@64.34.77.100:5061;tag=8651480-279398115-33554560-3987920819
To: sip:9990001@64.34.77.105;tag=as04b60228
Call-ID: 28038400e346a71080000002b3d7b2ed@64.34.77.100
CSeq: 1 INVITE
User-Agent: Asterisk PBX
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY
Supported: replaces
Proxy-Authenticate: Digest algorithm=MD5, realm=“asterisk”, nonce="51fd6533"
Content-Length: 0

Please anybody help me. You can also send me reply at zaeemabbas@hotmail.com. Any help would greatly be appreciated.

Regards
Zaeem