Re: "There's a routing problem I have glossed over..."

Rohit Khare (
Thu, 08 Oct 1998 12:32:46 -0700

Shepard's thesis, under Dave Clark, considered the routing problem in rando=
arrays of relays. His major finding was that routing hotspots were
unavoidable, generally in the physical center of the network. Congestion
would overcome.

I think the loophole is placement: if relays are not distributed randomly,
but rather in conjunction with human activity -- nay, *economic* activity -=
then hot-spots are not 'phantom': receiver congestion is precisely where
there are the most people. To the degree that each new relay 'mints' new
capacity -- which Shepard's EE seems to refute -- then 'downtown' doesn't
look like as much of a bottleneck. It'll be more expensive, but it won't
melt. Secondly, if congestion occurs in places with lots of human
infrastructure, there's also more "wormholes" to bleed off traffic pressure
into the
wireline infrastructure.

Nevertheless, the debate won't be won or lost by radio physics. We need
self-organizing routing for manageability, regardless of the medium. And
scared as I am that people are moving into this space commercially, I think
I can still stand by my case that the *real* tough nut to crack is the
socioeconomic model: trust relations that really do ground 'paranoid'
networks that have 'limited peripheral vision', and a standardized *TP
envelope system that can facilitate trade in messages rather than packets.

But I can't prove it. Traditional IP may even work at Shepard's scale.
Classical computer science my ass... but who says the guys/gals designing a
transciever net need to worry about having large local disks of cache and
key management and naming lookups and forwarding agents &c in themselves?
They, after all, are on the Right Side of layering. I feel rather soiled
myself arguing otherwise...


Engineer's wireless Internet-in-a-box draws interest
By Rick Boyd-Merritt
EE Times
(10/07/98, 9:04 p.m. EDT)

BELMONT, Mass. =8B What if people could go out and buy their own piece of the
Internet in the form of a $500 consumer-electronics black box instead of
relying on a giant communications service provider to dole out pieces of th=
network to them for a monthly bill? Strange as it seems, that is essentiall=
the idea proposed by Timothy J. Shepard, a self-employed communications

Just as people bought PCs and broke the hold that mainframe service centers
had on delivering computing services, Shepard thinks people will someday bu=
networks in the form of personal radio transceivers that become their
Internet-in-a-box. "Maybe we can all own our own telecom infrastructure whe=
we own our own radios," Shepard said. "If everyone had this you could cance=
your phone line."

Shepard describes a packet-based radio network made up of self-organizing
radios that cooperate to form a metropolitan area network =8B and maybe
someday even a global Internet. Signals pass from one neighbor to the next
across thousands or potentially millions of links. The vision, the basis of
his 1995 thesis at MIT, led him to leave a comfortable research job at GTE
Internetworking last April, and is now the seed for a startup company
Shepard hopes to build.

Since April, he said, "I've been having a great time and burning my savings

The 30-something engineer may not have to spend his own money much longer.
Following a presentation of his ideas at a recent telecommunications
conference, Shepard was courted by the likes of Hewlett-Packard, Mayfield
Fund and other would-be investors interested in his vision that energized a=
elite crowd at the Telecosm Conference in Squaw Valley, Calif., last month.

"Imagine people buying boxes and putting them on top of their houses and
those boxes organizing themselves into networks that can blanket a
metropolitan network," Shepard said in an interview at the conference.
"Everybody would own their own piece and as long as you were working across
the metropolitan area it would be entirely end-user financed =8B some people
say free."

More specifically, Shepard imagines a $500 consumer electronics box that
includes 6-mm-wave downconverter/upconverter radios each pointing in a
different direction working at a 2-GHz chipping rate and delivering a raw
data rate of perhaps 200 Mbits/second with a 15-ms delay. "You can already
get the components you need to make this, but they are very expensive," he

Cost reduction =8B a process that could take four to seven years =8B is just on=
of the hurdles Shepard sees ahead. "There's a lot of research that still
needs to be done," he said. "I've solved the hardest 10 percent of the
problems, but there are still plenty of issues about how to build the
microwave radios and the network infrastructure.

"There's a routing problem I have glossed over," Shepard said. That involve=
inventing "an addressing architecture and a way to tackle the problem of ho=
do you find what you want to get to and how do you get a route to that," he
said. "It's a classical computer science problem in the tradition of scalin=
large information systems, and I have a lot of faith that problem is

Indeed, Shepard's background is steeped in just such problem-solving. As a
graduate student at MIT, Shepard worked with the group that developed the
Multinix operating systems and helped lay the groundwork for some of the
Internet's architecture.
"They had no idea it would scale the way it has today," he said. "But they
got a lot of things close enough to design so that it was able to grow."

Oddly enough, Shepard's thesis was born from this tradition of large-scale
systems and the Internet in combination with his somewhat nerdy hobby: radi=

"I was doing hidden-transmitter hunting for sport," Shepard said. "Someone
would chain a box to a tree in the woods and it would transmit on the first
minute of every 15 and I had some friends with whom I'd go hunting for it
instead of writing our thesis as we should have done. We learned a lot abou=
radio propagation in the process of doing that."

At one point, Shepard lost faith in his vision of a self-organizing packet
network, believing it could not scale to a meaningful size. Indeed,
theoretically, as the number of radios approaches infinity the
signal-to-noise ratio on the network moves toward zero and no one can

"But if you look at what that ratio is at 10,000 stations or 10 million
stations, you can see for practical purposes the signal-to-noise ratio stop=
declining and effectively bottoms out at around one part signal to 100 part=
noise. You can plug that in to Shannon's capacity theorem and that tells yo=
what are the possibilities in radio systems engineering. That calculation
got me going again."

With that bit of math, and the probability of some venture-capital seed
money not far away, Shepard is back on track in his latest radio hunt. He
may not be alone. Word emerged at the Telecosm conference of at least two
other radio startups in the works with ideas not far removed from those of