Re: ICMP As A Diagnostic Tool?

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2 total messages Started by tsuchiya Wed, 08 Apr 1987 13:20

#1619

Author: tsuchiya
Date: Wed, 08 Apr 1987 13:20

27 lines
2033 bytes

From Miles Fidelman:
> It's been my observation that ICMP provides some useful functionality for
> isolating and diagnosing internetwork problems - e.g. by timing pings, 
> looking at what percentage of echos come back, source routing packets via
> specific paths, route recording, etc.
> 
> It strikes me that the lack of similar functionality for the OSI world may
> lead to an OSI internet in which significant classes of problems can not
> be fault isolated. I find this a rather scary thought.

It is not true that the OSI world lacks similar functionality.  ISO IP
ISO 8473) has error messages which covers everything ICMP does except
Redirect, Echo, and Timestamp, and Information.

The Redirect function in ISO is in the ES-IS (End System to Intermediate
System) routing protocol, DP 9542.  The Echo function can be accomplished
by using partial source route with the "echoing" machine on the list.
(This if the distant machine is an IS.)  To an ES, a transport connection
can be used much to the same, if not better, effect.

In addition, ISO is working on a suite of management functions and
protocols which will allow for much more detailed and flexible management,
debugging, etc., of networks.  I can't speak for all layers, but in ANSI
X3S3.3 (Network and Transport layers) we are actively working on this.

	Paul Tsuchiya		tsuchiya@gateway.mitre.org
	The MITRE Corp.		tsuchiya@mitre-gateway.arpa

Re: ICMP As A Diagnostic Tool?

#1625

Author: gds
Date: Wed, 08 Apr 1987 22:13

20 lines
1727 bytes

     The Redirect function in ISO is in the ES-IS (End System to Intermediate
     System) routing protocol, DP 9542.  The Echo function can be accomplished
     by using partial source route with the "echoing" machine on the list.
     (This if the distant machine is an IS.)  To an ES, a transport connection
     can be used much to the same, if not better, effect.

I believe one advantage to the way we do ICMP echoes is that, for all
the implementations I have heard of, processing of the echo reply takes
place in kernel space instead of user space.  The use of a user program
waiting on a transport connection to trap echoes and generate echo
replies requires scheduling of that process.  If the system is loaded,
it will lessen the accuracy of the round-trip time.

In case anyone is interested, I have some war stories describing the use
of ICMP for fault isolation.  (Example:  discovering that you have lost
your gateway, and finding a new one.)  They're too long to reprint here,
but might provide some amusing reading.

--gregbo

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