The problem is the the visited GK might (and probably) control firewalls and other QoS and security devices. Therefore it needs to know what my terminal is doing, and may disagree with the replies of my home GK. Also for security reasons my home GK may be restricted to receiving xRQs from the local zone and from specific GKs, and may reject xRQs sent from the open internet.
However, I agree with you that if there are no security or QoS issues, the GK is just a super directory that also controls access to gateways and in this case the terminal could contact his home GK directly.
De : Andrew Draper WVdevmt-WS[SMTP:adraper@DEV.MADGE.COM] Répondre à : Mailing list for parties associated with ITU-T Study Group 16 Date : Friday, August 21, 1998 11:26 AM A : ITU-SG16@MAILBAG.INTEL.COM Objet : Re: Comments on AT&T proposal
On Thu, 20 Aug 1998 17:53:41 +0200 Olivier HERSENT wrote:
Hi everyone,
Some time ago, we had some brainstorming on roaming with H.323. One of
the
simplest ways to do it was that the roaming terminal would send the
ARQ,
... to the visited network GK (discovered my broadcast/multicast). This GK would recognize from the calling party alias that the terminal si from
an
external administation having an agreement with the visited
administration.
It would then forward the xRQs to the home gatekeeper of the terminal
and
get the xCFs in reply.
This has many benefits :
- The home GK knows where is the roaming teminal and can forward calls.
- Any policy implemented at the home gatekeeper (restricted phone usage,
etc ...) is still enforced in any visited domain
- It is simple
So roaming might be a good reason to forward xRQs ... just my FF.02.
I agree that if I am a roaming user then I must be registered with my home gatekeeper. In addition to the reasons you give, my home gatekeeper is the only element in the system which is authorised (by my company) to spend money on my behalf when connecting to the PSTN via gateways.
However, I am not sure what is gained by my registering with the gatekeeper on the visited network. Surely an easier solution is for me to register directly with my home gatekeeper directly whether I am at home or roaming?
In fact it may make it simpler, since I no longer need to multicast in order to find the foreign gatekeeper, but can be configured with the address of my home gatekeeper before leaving home (or can look it up from my AliasAddress in the same way as I would if placing a call to it).
In addition to simplifying the model, this reduces the dependency on foreign gatekeepers implementing the protocol correctly.
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