Newsgroups: comp.protocols.tcp-ip
Path: utzoo!henry
From: henry@zoo.toronto.edu (Henry Spencer)
Subject: Re: LAT
Message-ID: <1991Jan11.212214.15475@zoo.toronto.edu>
Organization: U of Toronto Zoology
References: <12578@hubcap.clemson.edu>
Date: Fri, 11 Jan 1991 21:22:14 GMT

In article <12578@hubcap.clemson.edu> hubcap@hubcap.clemson.edu (System Janitor) writes:
>- LAT is optimized for terminal/host connectivity on a single LAN

Ah, so one never needs to connect one's terminal to a host that is not
on the same local network?  Gee, DEC, thanks for telling me.  I thought
otherwise. :-)

It is difficult to evaluate the accuracy of such claims when the LAT
specs are (last I heard) still secret.

My first reaction is "this sounds like marketing fluff".

>- LAT causes less of a burden on the CPU and the network 
>        "In preliminary test using KI Research's KiNet, DR Labs found
>        the DEC's LAT protocol imposed lower overhead on both the host
>        CPU and the network than TELNET...

This is *extremely* sensitive to implementation details.  My gut reaction
is that it says almost nothing about the protocols.

>       ...This difference is due in large part to the fact
>        that LAT does not use the full DECnet stack, whereas TELNET
>        uses the full TCP/IP stack...

Now this *is* marketing fluff.  Telnet uses the full TCP/IP "stack", all
two levels of it:  IP for data delivery, TCP for reliability, sequencing,
and flow control.  Unless the laws of nature have gotten repealed somehow,
LAT needs all those functions too.  I can think of no reason offhand why
a well-tuned TCP/IP implementation -- more often spoken of than found,
alas -- should incur any extra overhead compared to whatever LAT uses.

For a guess, they're comparing a user-level Telnet server implementation
against an in-kernel LAT server, and it is no surprise that the in-kernel
approach is more efficient.
-- 
If the Space Shuttle was the answer,   | Henry Spencer at U of Toronto Zoology
what was the question?                 |  henry@zoo.toronto.edu   utzoo!henry