I would like to hear people's interpretation of when a new service ID should be created in H.225.0 Annex G. (A service ID is used to identify a service relationship between two border elements).
There are three cases to consider:
Case #1: - a BE (border element) receives a ServiceRequest message from a BE with which it does not yet have a service relationship
Case #2: - a BE receives a ServiceRequest message from a BE with which it already does have a service relationship, but the terms of the service relationship are to be changed (eg, different security parameters)
Case #3: - a BE receives a ServiceRequest message from a BE with which it already does have a service relationship (ie, this ServiceRequest is refreshing the service relationship), and the terms of the service relationship are identical to the previous terms (eg, same security parameters)
My impression is that the following should happen in each case:
Case #1 - create a new serviceID in the ServiceConfirmation Case #2 - create a new serviceID because we are changing the parameters of the service relationship (it's becoming a new service relationship) Case #3 - do NOT create a new serviceID - the existing relationship is being refreshed, so we should continue to use the same serviceID
However, the wording of H.225.0 Annex G does not seem to say this. It seems that in ALL cases, a new serviceID should be created. To me, this seems to be incorrect, and I'm not sure that the original intent took into account case #3. I think that in case #3, we should not be creating a new service ID.
The following sections from H.225.0 Annex G are relevant:
[from section 1.8.2] service ID - This identifer identifies a particular service relationship session between two border elements. Whenever a border element receives a ServiceRequest message, it allocates a globally unique service ID and returns it to the sender of the ServiceRequest message in the ServiceConfirm message.
[from section 1.8.2.5] A border element may send a ServiceRequest message to a border element with which it has an existing relationship, with the intent that the terms of the original relationship be terminated and replaced with the new terms. Service relationships may have limited time to live. A border element may refresh the relationship by sending a new Service Request.
[from section 1.8.2.6] Every new service relationship is identified by a service identifier. Whenever a border element receives a new ServiceRequest message, it allocates a unique service ID and returns it to the sender of the service request message in the "service confirm" message. If the border element already has a service relationship with the border element that sent the ServiceRequest message, sending ServiceConfirmation indicates that the terms of the original relationship are terminated and replaced with the new terms.
Any comments? If people agree that the wording needs to be changed to unambiguously handle case #3, now is the time to speak up. The deadline for contributions for the Geneva meeting is fast approaching.
Michael Fortinsky ----------------------------------------------------------------- Senior Program Manager, IP Telephony Group, VocalTec Communications Ltd. Email: mike@vocaltec.com Tel: 972 9 9707768 Fax: 972 9 9561867