Re: [H225 Annex G] When to create a new service ID

Michael,

Looking into this further, I believe the Annex G text actually clarifies this (text includes text from the IG):

G.8.2.6 Service Confirmation A border element in receipt of a ServiceRequest message responds with a ServiceConfirmation message to indicate that it agrees to establish a service relationship. 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.

So, it would seem that if a new ServiceRequest is received, the serviceID would remain the same. It does not say that the service relationship itself is terminated, but the "terms of the original" (which I interpret as the security attributes or other things). I suppose it could be that a new ServiceID could be introduced, though-- particularly when one side believes that the service relationship has expired.

I believe one of the issues is that, prior to this text introduced into the IG, it was assumed that one and only one service relationship existed between two BEs. This new text (underlined and in red) suggests otherwise. Perhaps this is the real problematic point: we have introduced the ServiceID field unnecessarily. We have changed Annex G such that multiple service relationships may exist in parallel.

We have two ways to resolve this: 1.. Remove the serviceID field 2.. Add more text to clarify the usage of the serviceID field I believe option (1) is actually the better course of action. We have added this new field-- we can either deprecate it or just remove it entirely. By choosing (1), we eliminate the problem entirely.

If there are good reasons for having multiple service relationships (and there may be), I believe a number of sections need to be modified in order to make it clear that multiple relationships may exist as suggested in (2). As for the keep alive, I believe that would be handled by the statement in the IG that says all subsequent messages would contain the serviceID field. So, we can move forward with (2), I can see where a few sections of text discussing service relationships needs corrections.

Paul

----- Original Message ----- From: Michael_Fortinsky@vocaltec.com To: Paul E. Jones Cc: h323implementors@pulver.com ; h323implementors@imtc.org ; ITU-SG16@mailbag.cps.intel.com Sent: Sunday, October 22, 2000 5:53 AM Subject: Re: [H225 Annex G] When to create a new service ID

Paul,

Maybe I don't understand your point - I am not sure what you mean when you say "a new ServiceRequest". (I think this is the heart of the matter - what determines what is a NEW ServiceRequest?)

New service ID's are allocated and returned in the ServiceConfirmation message, not in the ServiceRequest message. Therefore, it is up to the border element that receives the ServiceRequest message to decide whether to allocate a new service ID or not. The question still remains - how are "keepAlive" ServiceRequests to be treated?

Another way of looking at the issue is as follows (maybe this is clearer):

If a BE sends a ServiceRequest message that does NOT contain a serviceID field, a new service ID is returned in the ServiceConfirmation message and a new service relationship is defined.

If a BE sends a ServiceRequest message that DOES contains a serviceID field, the BE that received the ServiceRequest must determine whether to return the same serviceID or a new one (ie, is there going to be a new service relationship or not)

- if the service parameters in the ServiceRequest are the same as those in the existing service relationship, this ServiceRequest message is a refresh of the existing service relationship and the ServiceConfirmation is returned with the same service ID as was in the ServiceRequest

- if the service parameters are different, then: - if the BE want to accept the new parameters, it sends a ServiceConfirmation that contains a NEW serviceID - this also indicates that the previous service relationship has ended

- if the BE does not want to accept the new parameters, it sends a ServiceRejection (that contains the serviceID from the ServiceRequest message) indicating that the new terms are rejected - the old service relationship is still in effect according to the old service parameters (as per section 1.8.2.7/H.225 Annex G)

Comments?

Mike

"Paul E. Jones" paulej@packetizer.com 10/22/00 04:02 AM

To: Michael_Fortinsky@VOCALTEC.COM, ITU-SG16@mailbag.cps.intel.com, h323implementors@imtc.org, h323implementors@pulver.com cc: Subject: Re: [H225 Annex G] When to create a new service ID

Michael,

My opinion is that, given that there is a ServiceRequest and a ServiceRelease and that one can initiate a new service relationship before terminating a previous service relationship, a new service ID shall be introduced with a ServiceRequest message and a BE should not send a new ServiceRequest with the same ID without first releasing the previous relationship.

I believe that's in alignment with your interpretation.

Paul ----- Original Message ----- From: Michael_Fortinsky@VOCALTEC.COM To: ITU-SG16@mailbag.cps.intel.com ; h323implementors@imtc.org ; h323implementors@pulver.com Sent: Wednesday, October 18, 2000 5:40 AM Subject: [H225 Annex G] When to create a new service ID

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