Registration failure

This is my first asterisk install and I have yet to connect.

[Mar 27 08:42:47] NOTICE[2632] chan_sip.c: – Registration for 'Ham@chicago-10.vtnoc.net’ timed out, trying again (Attempt #1304)
[Mar 27 08:42:47] NOTICE[2632] chan_sip.c: – Registration for '18037920706@chicago-1a.vtnoc.net’ timed out, trying again (Attempt #1304)
[Mar 27 08:42:47] NOTICE[2632] chan_sip.c: – Registration for '18037920706@chicago-1a.vtnoc.net’ timed out, trying again (Attempt #1304)
[Mar 27 08:43:07] NOTICE[2632] chan_sip.c: – Registration for 'Ham@chicago-10.vtnoc.net’ timed out, trying again (Attempt #1305)
[Mar 27 08:43:07] NOTICE[2632] chan_sip.c: – Registration for '18037920706@chicago-1a.vtnoc.net’ timed out, trying again (Attempt #1305)
[Mar 27 08:43:07] NOTICE[2632] chan_sip.c: – Registration for '18037920706@chicago-1a.vtnoc.net’ timed out, trying again (Attempt #1305)
[Mar 27 08:43:27] NOTICE[2632] chan_sip.c: – Registration for 'Ham@chicago-10.vtnoc.net’ timed out, trying again (Attempt #1306)
[Mar 27 08:43:27] NOTICE[2632] chan_sip.c: – Registration for '18037920706@chicago-1a.vtnoc.net’ timed out, trying again (Attempt #1306)
[Mar 27 08:43:27] NOTICE[2632] chan_sip.c: – Registration for '18037920706@chicago-1a.vtnoc.net’ timed out, trying again (Attempt #1306)

I use viatalk and I used the sip.conf and extensions.conf

Please help!