Backward compatability H245Tunneling V4 with V3,2,..

Chris Wayman Purvis cwp at ISDN-COMMS.CO.UK
Tue May 22 09:34:58 EDT 2001

That's one way of doing it, but CallProceeding is not an end-to-end message,
so it's conceptually wrong.  How hard is it for your gatekeeper to translate
between tunnelling and non-tunnelling?  Another reasonable way of doing it
is always to respond that tunnelling IS possible, and do the translation in
the gatekeeper.


danlee at YNNMAIL.COM wrote:

> According to ver.4 "If the called entity does not yet know if H.245 tunneling can
> be supported, it shall include the provisionalRespToH245Tunneling flag. This may
> happen, for example, when a Gatekeeper is responding to a calling entity with a
> message such as Call Proceeding before the called endpoint responds to the
> h245Tunneling flag. "
> The problem arises when the calling entity does not support this flag (i.e., does
> not yet support ver.4). E.g.,
> 1. Calling entity (let's say ver.3 EP) is sending Setup with indication of the
> tunneling support.
> 2. The gatekeeper answers with Call Proceeding including h245Tunneling ==False
> and provisionalRespToH245Tunneling ==True.
> 3. The calling entity (that was implemented BEFORE ver.4) will understand this
> as "tunneling is not supported".
> 4. But the called entity can send tunneled messages.
> What we've decided is:
> 1. To check the supported version of the calling EP.
> 2. If the version is >=4 than above scenario may be used.
> 3. Otherwise Call Proceeding will be delayed until getting the information from
> the called EP.
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Dr Chris Purvis -- Development Manager
ISDN Communications Ltd, The Stable Block, Ronans, Chavey Down Road
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