Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 9/5/84; site wucs.UUCP
Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!ihnp4!wucs!jst
From: jst@wucs.UUCP (Jon Turner)
Newsgroups: net.dcom
Subject: Re: Packetized Voice
Message-ID: <963@wucs.UUCP>
Date: Sun, 19-May-85 19:23:08 EDT
Article-I.D.: wucs.963
Posted: Sun May 19 19:23:08 1985
Date-Received: Mon, 20-May-85 04:41:56 EDT
References: <416@wdl1.UUCP> <1294@ecsvax.UUCP>
Reply-To: jst@wucs.UUCP (Jon Turner)
Organization: Washington U. in St. Louis, CS Dept.
Lines: 59
Summary: 

John Nagle writes
>       Packet voice seems to be one of those futuristic ideas, like monorails,
> whose time has passed.
> ...
> The only
> real justification for packet voice seems to be for high-reliability 
> jam-resistant military systems.
> 
Not true. Packet voice offers two main advantages over circuit-switched voice.
First, it requires less than 40% of the bandwidth, since there is no need
to tie up the channel during silent periods. Second, it integrates voice and
data in a single communication network. The primary beneficiary of this
integration is data, since the size of telephone networks offers economies
of scale that aren't available in pure data packet switches. The expectation is
that an integrated packet network can bring the cost of high speed data
communication down to an affordable level for residential customers.

When I was at Bell Labs, I worked on a project (called the Fast
Packet Network or FPN) whose purpose was to demonstrate the feasibility
of packet voice on a large scale (ie. replace the current circuit
switched voice network with a packet network). Many of the ideas behind
this project were not new. BBN has been in this game for a long time as
John pointed out. Anyway, the project was successful in demonstrating
that packet voice is not only feasible, but cost-competitive with
circuit-switching (something that almost no one in the telephone world
would have believed at the time). Since leaving the Labs about two years
ago, I've lost touch with the project and have no specific knowledge of
their plans, but they are continuing to work on it, and rumor has it that
they are running a field trial in California. On the whole, they've been
fairly quiet about it, but occasionally some tidbits leak out. Some of
the basic FPN patents have been issued recently, which has taken the lid
of the publication restraints that Bell had imposed previously. I've
recently written a paper describing the basic technology and giving the
arguments in favor of an integrated packet network as an alternative to
the much heralded, Integrated Services Digital Network. I'll be happy
to send copies to anyone interested.

GTE has been doing similar work using a different switching technology,
which they call burst-switching. This has been described in a couple of
articles in the IEEE Communications Society magazine. Burst-switching is
essentially a fast circuit switching scheme in which a circuit is established
and taken down for each burst of information (voice, data or whatever).
It's more geared towards voice than the packet switched approach and is
in my opinion less flexible, but the objectives of this work and the FPN
work are clearly similar.

In summary, I think it's premature to write off packet voice as idea
whose time is past.

Jon Turner 	Washington University in St. Louis 314-889-6193
UUCP:		jst@wucs.UUCP  or  ..!{ihnp4,seismo}!wucs!jst
ARPANET:	wucs!jst@seismo.ARPA
CSNET:		wucs!jst@seismo.ARPA%csnet-relay
-- 

Jon Turner 	Washington University in St. Louis 314-889-6193
UUCP:		jst@wucs.UUCP  or  ..!{ihnp4,seismo}!wucs!jst
ARPANET:	wucs!jst@seismo.ARPA
CSNET:		wucs!jst@seismo.ARPA%csnet-relay