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
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Senior Program Manager, IP Telephony Group, VocalTec Communications Ltd.
Email: mike@vocaltec.com Tel: 972 9 9707768   Fax: 972 9 9561867