Token rings, error reporting in

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3 total messages Started by jbn Thu, 23 Jan 1986 06:17

#904

Author: jbn
Date: Thu, 23 Jan 1986 06:17

18 lines
1664 bytes

     One annoying problem with Ethernet-type systems is that you send
blind; there's no link-level indication that nobody is listening to you.
This causes some problems in adaptive routing that I won't go into here.
     This ought not to be a problem with token rings, since the receiver
usually takes the message off the ring and replaces it with the token.
(You could cheap out and let the sender take it off the ring, but it
halves the ring bandwidth if you do, of course.)
If the sender sees a message with its own source address go by, it has
to remove it to prevent it going around forever, and this indicates a
failure to deliver the message.  (You could really cheap out and let the
ring time out and regenerate the token whenever this happens, but then
sending to a dead node will tie down the ring for some time.)
     Which token rings actually provide indication of non-delivery to the 
sender?  I've been told that the Cambridge Ring does and Proteon does not.
Who has hard information on this?

					John Nagle

Re: Token rings, error reporting in

#910

Author: Mark Rosenstein
Date: Fri, 31 Jan 1986 20:52

22 lines
1508 bytes

In article <952@wdl1.UUCP> jbn@wdl1.UUCP writes:
>
>     Which token rings actually provide indication of non-delivery to the 
>sender?  I've been told that the Cambridge Ring does and Proteon does not.
>Who has hard information on this?
>
>					John Nagle

The Proteon proNET ring does have hardware acknowlegement.  The sender
removes the packet from the ring, not the receiver.  However, the receiver
does reset a bit at the end of the packet as it goes by if it was received
successfully.  In this way broadcast can work the same as sending regular
packets.
					-Mark Rosenstein

work:	mar@proteon.arpa	(617) 655-3340
other:	mar@borax.lcs.mit.edu	(617) 497-4863
	...ihnp4!mit-eddie!mar

Disclaimer: I do work for Proteon, but as a programmer not a hardware
person.  I think I've just told the truth, although this is not an
official statement of Proteon, Inc.

Re: Token rings, error reporting in

#922

Author: taylor
Date: Tue, 04 Feb 1986 20:05

15 lines
1393 bytes

In article <952@wdl1.UUCP> jbn@wdl1.UUCP writes:
>     Which token rings actually provide indication of non-delivery to the 
>sender?  I've been told that the Cambridge Ring does and Proteon does not.

Actually, Cambridge Ring is a *slot* ring. However, in a slot ring, if you
see the mini-packet you sent not marked as recieved ( in fact there are 4
different statuses/stati it could have - accepted, rejected, no-one there
and another ... ), that is, unmodified except for the 'monitor-passed' flag,
you know your addressee is not on the ring.
 There's no problem about loss of token, because there's no token ...

-Jem-
-- 
JANET: taylor%glasgow.uucp@uk.ac.ed.cstvax          -o        Jemima
UUCP:  { uk }!cstvax!glasgow.uucp!taylor             (==).     Puddleduck

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