Subject: Internet Telephony Gateway Location

From: "Jonathan D. Rosenberg" <[email-masked]>
Date: Mon, 28 Jul 1997 18:31:00 -0400

Members of the mmusic wg,

You may have just seen a recent announcement for an I-D on "Wide Area
Service Location", submitted to the Service Location (svrloc) wg.
Although this draft discusses services in general, it pays particular
attention to the problem of Internet Telephony Gateway (ITG) location,
and may be of some interest to people on this list.

Henning and I were concerned with the problem of how an IP host might
find an Internet Telephony Gateway (ITG). These devices effectively
bridge (at the application layer) IP networks and the public switched
telephone network (PSTN), allowing an IP telephony user to call a plain
PSTN end-point. For cost reasons, it is desirable to use a gateway
closest to the PSTN callee. This would reduce the telephone charges
incurred by the ITG, which presumedly get passed on to the IP host using
that gateway. We came up with a protocol architecture which would allow
IP hosts to find any gateway on the Internet which meets some arbitrary
set of constraints, including cost, protocol support (H.323, SIP, etc),
proximity to the IP host, etc. We then realized that our architecture
fits quite nicely as an extension to the service location protocol (now
RFC 2165), and generalizes to any service, of which an ITG is just an
example.

The main idea is to use a scalable multicast advertisement mechanism
(like the one in RTCP) for announcing services. These can then be
collected by a device we call a broker. This device can be contacted by
clients seeking services, and queried for those services which meet some
constraints. The draft also discusses issues such as the representation
of cost of a telephone call (not an easy problem), and authentication.

I will be taking a few minutes at Munich to present this draft to the
svrloc wg. In the interim, I welcome any comments or questions. You can
find a copy of the draft at either:

ftp://ds.internic.net/internet-drafts/draft-ietf-svrloc-wasrv-00.txt

or at:

http://www.cs.columbia.edu/~jdrosen/papers/draft-ietf-svrloc-wasrv-00.txt

Thanks,

Jonathan R.
-- 
Jonathan D. Rosenberg                       Lucent Technologies
Member of Technical Staff                   101 Crawfords Corner Rd.
High Speed Networks Research                Holmdel, NJ 07733
PHONE: (908) 949-6418                       Rm. 4D-534B
FAX:   (908) 834-5379
EMAIL: [email-masked]
URL: http://www.cs.columbia.edu/~jdrosen