H.323's "keepAlive" mechanism

Chris Wayman Purvis cwp at ISDN-COMMS.CO.UK
Mon Jan 29 10:07:33 EST 2001

> According to the text in section of H.323v4 (11/2000), as a response
> to a RRQ, a GK may respond with an RCF containing a timeToLive that is equal to
> or less than the timeToLive from the RRQ. This raises two questions:
> 1) Why isn't it allowed for a GK to respond with a greater value, or any value for
>    that matter?

There's no point.  After all, the endpoint is permitted to renew its
registration earlier than necessary, so if the gatekeeper put in a longer
timeToLive an endpoint would not lose by (and probably would) use its preferred
value anyway.

> 2) If the EP does not specify a timeToLive, should this be treated as a value
>    of "0" and does this make it impossible for a GK to impose any timeToLive
>    value?

I would suggest that this would imply that the endpoint does not support this
feature.  I would, on the other hand, have thought (unless one of the standards
says otherwise) that a value of "0" would mean that the registration expires
immediately, which may not be terribly useful!  Not quite the same thing.

Dr Chris Purvis -- Development Manager
ISDN Communications Ltd, The Stable Block, Ronans, Chavey Down Road
Winkfield Row, Berkshire.  RG42 6LY  ENGLAND
Phone: +44 1344 899 007
Fax:   +44 1344 899 001

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