On Wed, 2 Sep 1998 10:37:32 +1000 Douglas Clowes wrote:
From my POV, this underscores the need for thought on the Back End Services, both in terms of the services to be offered, and the protocol(s) to support those services.
Just for my information, where does the term Back End Services come from? Is this related to some sort of protocol currently run by telcos (SS7 database services for example)?
Does the term always refer to a third server somewhere else which communicates with both the originating and destination border elements?
While discussing billing, I assume that we are only discussing payment from the originating administrative domain to the destination administrative domain and that we are not discussing payment to the transport network providers (such as ISPs) for QoS connections (such as those set up by RSVP).
Here, it is fairly clear that authentication and billing is a Back End Service. The available destinations for a call may be dependent on the (authenticated) identity of the caller.
Yes, I agree that some entities will reject SETUP messages which are not authenticated and do not provide a suitable payment token. However, I think we should try hard to design a protocol which will not cause hopeless (bound to fail) SETUP messages to be sent. This is important because a) SETUP messages create state in the recipient and b) SETUP messages may involve charges to the originating administrative domain.
Later on in this message I use the term "setup requirements" to refer to a description of setup messages which the destination administrative domain will accept. Examples would be "you must authenticate using mechanism X (and server Y)" or "you must pay using method Z" (are there any other forms of setup requirement?). I use the term "setup capabilities" to refer to the set of mechanisms which the originating border element is able to send in a SETUP message (because they have been implemented and enabled).
The "token" to be included in theSetup message is produced by the Back End Service and may well be destination sensitive.
I agree.
Which raises the possibility of address translationalso being a back end service.
In the sense of having a third party server (not belonging to the originating or destination administrative domain) perform address translation I agree.
Back-End Services (may) include:
o caller identification, authentication, and authorisation; o address translation, gateway location; o call pricing; o call detail recording, billing, and settlement;
By my understanding of the term back-end services (which might be wrong) call pricing is for the destination administrative domain and is unrelated to any third party server. Call detail recording is also a problem only for the destination administrative domain.
which are all interrelated
Out of interest, are you expecting/requiring that the services provided by each of your bullet points must be provided by the same third party server (or would using one server for address translation and another for billing be acceptable). If not then how are they all interrelated?
and, in total, outside the scope of thegatekeeper to gatekeeper communications.
I disagree. Here are my reasons for thinking that identifying the requirements of the destination administrative domain fall within the scope of communications between administrative domains (an important subset of gatekeeper-gatekeeper communications).
To prevent hopeless SETUP messages from being sent the originating border element (or a third party) needs to work out the intersection of its setup capabilities and the destination border element's setup requirements.
As far as I can tell there are three ways for the originating BE to find out the destination administration domain's setup requirements:
a) It can find out during the resolution stage (the stage where an email-ID or E.164 number is translated to the address of a border element).
b) It can find out during the LRQ/LCF exchange.
c) We could design an extra protocol which is used before/after LRQ/LCF to let the originating BE find out what the requirements of the destination BE are.
For an email-ID type destinationAddress using the DNS to find the destination border element seems non-controversial. DNS only provides the name and address of the destination, so method a is not appropriate.
In this case I favour method b over method c for two reasons: firstly because it reduces the number of round trips required for a call setup and secondly because requirement 7 (of the latest annex G draft "diff0201.doc") suggests that the minimum number of changes to existing protocols should be made.
The E.164 to border element address protocol is as yet unspecified, so it could return the requirements of the destination administrative domain at the same time as it returns the address to which to send LRQ.
If the E.164 number resolves to an administrative domain which can be contacted directly then this doesn't seem to help much (as only one address is provided to which an LRQ must be sent anyway - so there are no efficiency savings to be made).
If the E.164 number would resolve to one or more third party gateways (eg. for a POTS number) then passing the setup capabilities of the originating border element might help narrow down the responses which the resolution server returns. However this has security implications and so should be a choice for the originating BE. We still need a mechanism for the originating BE to ask the destination BE about its setup requirements if it is being paranoid and not telling the resolution server.
Hope this makes sense (and my assumptions aren't too wildly different from yours).
Regards,
Andy.
-- Andrew Draper - Principal Development Engineer - WAVE Software Madge Networks, Wexham Springs, Framewood Road, Wexham, Berks. mailto:adraper@dev.madge.com phone:+44 1753 661329 pgp fingerprint D6 ED 72 4F 96 BB CA 2D 68 74 4C E0 CB B9 0B 3F