Howto:How to tweak the RAS and TCP Keepalive timers

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In rare case, the standard TCP and RAS timings can be less than optimal. Here is how to tweak.

Applies To

This information applies to

  • All IP devices

Build V6 SR1 and later.

More Information

Problem Details

In some scenarios it seems to be desirable to adapt the various call-related timeouts to local requirements.

There are 2 areas: TCP and RAS timeouts. The latter mainly affects the detection of missing RAS connections while the TCP settings affect the detection of calls broken due to lost IP connectivity.

The configuration is done in the config file.

TCP Configuration

You can set the frequency of TCP keep-alive packets between 1 and 1000 seconds (default 120) as well as the number of retries before the connection is considered broken between 2 and 1000 times (default 6).

config change IP0 /tcp-prio-keepalive n /tcp-prio-missalive n

RAS Configuration

RAS is UDP based, so TCPs layer 2 retry mechanism cannot be used. Instead, four RAS timing parameters can be set

  • Proposed Time to Live (ras-rrq-ttl)
This is the number of seconds after which the registration request to the Gatekeeper has to be refreshed (a.k.a. lightweight registration). You can set this to a value between 10 and 1800 seconds, the default is 1000. Please note that this value is proposed to the gatekeeper which will respond with a modified (most likely lower) number. An innovaphone gatekeeper will respond with a value of 120 for example.
  • Max Retries (ras-retry-count)
The number of retries for a lightweight registration before the registration is considered broken when no response is received. The RAS client will start with lightweight registrations when 90% of the negotiated "Time to Live" has expired. The registration is retried every "Request Timeout" seconds
  • Request Timeout (ras-request-timeout)
This is the number of seconds after which a request is considered lost if there is no response. You can set that to a value between 1 and 32768 seconds, the default is 2
  • Restart Timeout (ras-restart-timeout)
When a registration is lost, a new full registration is tried after this timeout. You can set this to a value of 10 to 32768 seconds, the default is 30. Please not that if the RAS client has received an unregistration request from the gatekeeper, it will restart the registration procedure immediately not waiting for the restart timeout to expire. This is to make sure that the RAS client will quickly re-register with the gatekeeper when the gatekeeper has been restarted gracefully

Here is the command syntax:

config change H323 /ras-rrq-ttl n /ras-retry-count n /ras-request-timeout n /ras-restart-timeout n
Setting the parameters through the web interface

These settings are not available in the web user interface by default. However, you can enable the configuration web pages with these commands:

config change CPU /tuning

This will work only on IP200A, IP230, IP150

Known Problems

Be careful and know what you are doing as you can easily screw up an installation by configuring bad settings.