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From: henry@utzoo.UUCP (Henry Spencer)
Newsgroups: comp.dcom.lans,comp.protocols.tcp-ip,comp.protocols.misc
Subject: Re: Higher speed LANs ?
Message-ID: <8202@utzoo.UUCP>
Date: Thu, 25-Jun-87 13:23:49 EDT
Article-I.D.: utzoo.8202
Posted: Thu Jun 25 13:23:49 1987
Date-Received: Thu, 25-Jun-87 13:23:49 EDT
References: <541@houxa.UUCP>
Organization: U of Toronto Zoology
Lines: 60

> Is anyone working on higher speed LANs? ...

The wave of the (near) future is probably FDDI, an impending ANSI (?)
standard 100-Mbit/s fiber network.  There will presumably be interest
in pushing its speed up further as well.

> What are the issues that keep us down at such low [net] rates?  The disks
> themselves are now in the 500K to 2Meg bytes per second range. 
> Backplanes and memory are up in that range.  Certainly, interface
> logic can go that fast (it does to disks, why can't it to LANs?).

The interface hardware, on the whole, does/can go that fast.  However...
Can you say the nasty word "protocols"?  The problem is that neither the
disks nor the other things you mention are contending with the problems
of sending data over long distances on multiple-host unreliable gatewayed
networks.  If you work hard at it and have the right hardware, you can get
a good fraction of the Ethernet bandwidth by using very specialized software
that ignores most of these problems, but the solutions don't generalize
easily.  Many of the issues also either aren't well understood or haven't
been well understood until fairly recently.  To slightly paraphrase an
observation that has been made in other connections:  "networks don't really
pose any fundamentally new problems, they just break all the old kludgey
special-purpose solutions".

It is also worth mentioning that most current protocol implementations,
like most current software in general, really haven't had much attention
paid to performance in their design or implementation.

> Are there fundamental problems with TCP/IP that limit its application
> to higher speed use?

I'm told that the answer is more or less "yes".  Remember that TCP/IP dates
from the Neolithic age of network protocols (which wasn't very long ago).

> Are the new ISO protocols better for high speed file transfer?

Fat chance.

> ...  Can the high speed backbone fiber
> networks be made to handle individual computer to computer or
> computer to terminal traffic?  Or, it there some fundamental issue
> that keeps them in the LAN to LAN bridging application?

No reason why they can't work for more local traffic, but they are relatively
costly and there has been no standard, which has discouraged such use.  The
standardization of FDDI should help.

> I know that there are propritary protocols and links that go much
> faster, but is it necessary to throw out the standards and ability
> to internet and use diverse equipment and applications to get the
> higher speed?

The combination of FDDI hardware and lightweight transport protocols
supported by special hardware -- see Greg Chesson's paper in the latest
Usenix for a very interesting example -- has a reasonable chance of giving
us the speed without sacrificing interconnection and internetworking.  It
*will* take a little while before everybody is set up to do this, though.
-- 
"There is only one spacefaring        Henry Spencer @ U of Toronto Zoology
nation on Earth today, comrade."   {allegra,ihnp4,decvax,pyramid}!utzoo!henry