Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!hellgate.utah.edu!wasatch!haas
From: haas@wasatch.utah.edu (Walt Haas)
Newsgroups: comp.dcom.lans
Subject: Re: What services does X.25 provide?
Keywords: x.25, services, login, e-mail, file transfer, IPC
Message-ID: <3290@wasatch.utah.edu>
Date: 11 Sep 89 16:54:39 GMT
References: <796@maxim.erbe.se> <3279@wasatch.utah.edu> <522@wet.UUCP>
Organization: University of Utah, College of Engineering
Lines: 23

In article <522@wet.UUCP> epsilon@wet.UUCP (Eric P. Scott) writes:
>In article <3279@wasatch.utah.edu> haas@wasatch.utah.edu (Walt Haas) writes:
>>                      But the X.25 standard defines reliable data
>>transmission over virtual circuits, with a means of addressing, much as
>>TCP/IP does.
>
>It doesn't meet the Internet's definition of reliable.  If you
>don't want to see your VCs reset everytime someone sneezes, you
>should run a truly reliable protocol (e.g. TCP) on top of X.25.

Unfortunately the Internet's definition of "reliable" isn't reliable,
since the TCP layer gives no notice at all when the route to the remote
host goes down.  Bear in mind that TCP is a military protocol designed
primarily for an environment in which a hostile enemy is shooting holes
in the network, and many compromises are forced on TCP users in order
for the protocol to meet this goal.  In the world of commercial applications
that most of us work in, the environment and requirements are far different
from the military world.  The massive inefficiencies forced by using
military protocols for everything regardless of the environment would
preclude TCP/IP from civilian use if the government didn't heavily subsidize
its use.

-- Walt Haas     haas@cs.utah.edu    utah-cs!haas