To prevent disconnections on client side in your SSH terminal you can add this parameter to the configuration file /etc/ssh/ssh_config:
Basically this option will send a null packet to the remote host every 100 seconds and will keep alive the connection.
If you get this message on logs:
VFR-4-FRAG_TABLE_OVERFLOW: Dialer0: the fragment table has reached its maximum threshold 16
usually indicates than you are receiving a high number of fragmented packets. It may happens using p2p applications like torrent or emule, under an fragmentation packet attack or another causes.
You can increase this value and check if warnings disappear:
router(config-if)#ip virtual-reassembly max-reassemblies 64