Re: host down (was ..."layering violations")


mnetor!utzoo!yetti!geac!daveb@uunet.uu.net
10 Nov 87 19:56:52 GMT


In article <8711030915.AA00844@gumby.wisc.edu>
        Mitchell Tasman (g-tasman@GUMBY.WISC.EDU) writes:
[discussion of the behavior on "host down"]... a daemon
| should immediately close the associated TCP connection.
|
| With an 1822 Distant Host connection to DDN, this may be a fairly
| reasonable approach. However, a typical DDN connection of late has been
| X.25 or HDH. Here, "host down" may have a more transitory meaning: simply
| that there was noise on the host access line. The remote host may well
| reappear with all TCP connections intact.

  My experience with short-haul or secondary nets has been that
there are two distinct kinds of events which TCP might regard as a
"host down".

  One is a real host-down and the other is the aforementioned QRN
(noise) on the line. The latter is particularly annoying on what is
supposed to be a low-error medium...

  Methinks that TCP is being a bit pessimistic: IP is not supposed
to be error-free, and I suggest that TCP may be misinterpreting the
errors which a short-haul network seems to love to produce as a more
serious and long-term event than it really should.

  Could map or someone comment?

 --dave (on the other hand, i could be biting my foot) c-b

--
 David Collier-Brown.		      {mnetor|yetti|utgpu}!geac!daveb
 Geac Computers	International Inc.,   |	 Computer Science loses	its
 350 Steelcase Road,Markham, Ontario, |	 memory	(if not	its mind)
 CANADA, L3R 1B3 (416) 475-0525	x3279 |	 every 6 months.



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