Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!tut.cis.ohio-state.edu!ucbvax!LCS.MIT.EDU!MAP
From: MAP@LCS.MIT.EDU (Michael A. Patton)
Newsgroups: comp.protocols.tcp-ip
Subject: SO_KEEPALIVE considered harmful?
Message-ID: <8906072222.AA25735@gaak.LCS.MIT.EDU>
Date: 7 Jun 89 22:22:40 GMT
References: <8905301407.AA03344@uunet.uu.net>
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 44


   From: prisma!mo@uunet.uu.net
   Date: Tue, 30 May 89 08:07:02 -0600

   [...]  According to the advertising copy, TCP provides reliable
   virtual circuits.  In my book, knowing that the other end has
   croaked is part of the definition of "reliable."

But just because you aren't getting replies does NOT mean the other
end "croaked", just that something did.  If it's internal to the
network, it should recover and you can continue.  The indication that
the other end "croaked" is receiving a RST!  How an application deals
with being temporarily partitioned has to be up to that application.
There are just too many possibilities.
						     Since this is
   mechanism that is going to have to be reinvented by lots of
   protocols, it makes sense to get it right ONCE [...]

But there isn't one right answer so how can we "get it right ONCE"?
The whole argument here is that the BSD implementation goes against
the design of TCP in that they chose one specific requirement and
implemented a solution to it ONCE, but what I want is NOT what they
provide and what the guy in the next office wants is not what I want.
No strategy that is built into the TCP layer will be right for all
applications, and it can get in the way of applications that want some
other specific type of handling for these cases.

	[...] so people don't have to (1) reinvent all the bugs and
   (2) can just use it for what they really want to be doing.

But you don't have to break TCP (oops, I mean add to it) to prevent
people from reinventing things.  Provide them with a library of
different techniques for handling various network problems.  If I want
one of the standard techniques, I just use it.  If I want something
special, I write it (and if it's of general use, it's an addition to
the library).

	    __
  /|  /|  /|  \		Michael A. Patton, Network Manager
 / | / | /_|__/		Laboratory for Computer Science
/  |/  |/  |atton	Massachusetts Institute of Technology

Disclaimer: The opinions expressed above are a figment of the phosphor
on your screen and do not represent the views of MIT, LCS, or MAP. :-)