Backward compatability H245Tunneling V4 with V3,2,..

danlee at YNNMAIL.COM danlee at YNNMAIL.COM
Tue May 22 07:17:11 EDT 2001

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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