All,

I'm resending this (originally sent it to the h323 implementors list) and forwarding it additionally to other people in the hope of getting a reply! If anybody is using this field for anything at all, PLEASE tell me what you want in it!

My apologies to those on multiple lists, who will receive this multiple times, but I could really do with some responses and didn't get any from the obvious list!

Chris ------------------------------------- All,

What purpose do the sourceInfo and destinationInfo fields have in H.225.0 messages such as Setup and Alerting? The description in H.225.0 says that it "contains an EndpointType to allow the called party to determine whether the call involves a gateway or not". The specific questions that arise are:

1) What difference does it make? Why does anybody care whether there's a gateway in the call?

2) What information do vendors intend to supply in any of the gatewayInfo, terminalInfo or mcuInfo fields in the EndpointType? I note that only the gatewayInfo field has standard parameters defined, which allows you to specify what protocol you're gatewaying to. Whilst this might be useful information to supply in registrations with a gatekeeper, how does it help an endpoint in the call signalling phase?

3) What is the "correct" procedure for a gatekeeper that is routing these messages (or a proxy, come to that)? Should it a) Pass these fields through unchanged? b) Put in its own information instead of what's already there? (i.e. build a new EndpointType element with GatekeeperInfo supplied and filling in the vendor field with vendor information for the gatekeeper) or c) Add its own information to what has already been supplied? Note that, bearing in mind that the call may easily be routed by two gatekeepers - even without any enhancements to interGK communication - this means that only information from the destination endpoint's gatekeeper will be present? Again, should the vendor information within the EndpointType SEQUENCE be that of the GK, or whatever was supplied by the original calling entity?

Chris ---------------------------------------- Dr Chris Purvis - Senior Development Engineer, WAVE CC Software Madge Networks Ltd, Wexham Springs, Framewood Road, Wexham, Berks. Phone:+44 1753 661359 email: cpurvis@madge.com