To connect to a NORTEL trunk from asterisk your context should look liek this
username@mydomain.com:000000:username@99.99.99.99/6144444444
username=your username on the nortel sstem
mydomain.com = your domain (when logging in through the web its username@domain)
00000 = your password
99.99.99.99= Your PROXY server
6144444444=your DID
context:
username=Username
fromuser=Username
secret=000000
outboundproxy=99.99.99.99
fromdomain=mydomain.com
host=mydomain.com
type=friend
insecure=port,invite
context=from-trunk
Registration as follows
username@mydomain.com:000000:username@99.99.99.99/6144444444