TCP/IP Network Characteristics 7-19
Setting the TCP Keepalive Timer
Setting the TCP Keepalive Timer
What the Timer Does
The TCP keepalive timer determines whether a TCP connection with a remote host is
active and should remain open.
After the access server and a remote host establish a TCP connection, the access server
waits a set amount of time and sends a keepalive probe to the remote host. If the access
server receives a valid response from the remote host, it waits again and sends a new
keepalive probe.
If the access server does not receive a response from the remote host, it continues to
send keepalive probes until it reaches a set maximum. If the remote host does not
respond after the access server sends the last keepalive probe, the access server drops
the connection.
Setting the Timer
Use the SET/DEFINE/CHANGE INTERNET [TCP] KEEPALIVE TIMER command
to set the amount of time (in minutes) the access server waits to send the first keepalive
probe after establishing a TCP connection with an idle remote host. The range is from
1 to 1440 (one day) and the default is 120 (2 hours).
Timer Set Example
The following example shows how to set the TCP keepalive timer to wait one minute
before sending the first keepalive timer:
Local> CHANGE INTERNET TCP KEEPALIVE TIMER 1
Disabling the Timer
By default, the TCP keepalive timer is enabled. Use the SET/DEFINE/CHANGE
INTERNET [TCP] KEEPALIVE TIMER DISABLED command to disable it.
Setting Timer Retries
Use the SET/DEFINE/CHANGE INTERNET [TCP] KEEPALIVE RETRY
command to set the number of keepalive probe retries. The TCP keepalive timer retry
number indicates the number of times that the access server sends keepalive probes to
the remote host when it does not receive a valid response. The access server sends a
keepalive probe every minute until the host responds or it reaches the retry count value.
The retry count value range is from 1 to 60 and the default value is 8. If the access
server does not receive a valid response from the remote host after sending the last
probe, the access server drops the connection.
