PBX - Closing session because connection timedout after 33 seconds

General Help
1

Hello,
I am having this problem with PBX server, the server keeps on dropping connection of ip iphones from Cisco. This is the message I get when check the asterisk directory log files. Can some one help me troubleshoot this problem , that will be very much appreciated.

[2013-09-26 16:47:57] NOTICE[11832] sccp_socket.c: MAC-XXXXXXXX: Closing session because connection timed out after 33 seconds (timeout: 33000).
[2013-09-26 16:48:04] NOTICE[11842] sccp_socket.c: MAC-XXXXXXXX: Closing session because connection timed out after 33 seconds (timeout: 33000).
[2013-09-26 16:48:06] NOTICE[11840] sccp_socket.c: MAC-XXXXXXXX: Closing session because connection timed out after 33 seconds (timeout: 33000).
[2013-09-26 16:48:07] NOTICE[11841] sccp_socket.c: MAC-XXXXXXXX: Closing session because connection timed out after 33 seconds (timeout: 33000).
[2013-09-26 16:48:10] NOTICE[11838] sccp_socket.c: MAC-XXXXXXXX: Closing session because connection timed out after 33 seconds (timeout: 33000).
[2013-09-26 16:48:10] NOTICE[11862] sccp_socket.c: MAC-XXXXXXXX: Closing session because connection timed out after 33 seconds (timeout: 33000).

2

This is not a FreePBX issue. chan_sccp is not part of our project.