ICMP in ISO


Paul Tsuchiya (tsuchiya@gateway.mitre.org)
Tue, 14 Apr 87 12:58:29 EDT


>From John Shriver:
> Another important aspect of ICMP echo reply is that it is Mandatory in
> the TCP/IP suite (see the latest Official ARPA Internet Protocols,
> where IP and ICMP are the only Mandatory protocols). Using
> transport-level protocols in ISO for the same function will not be
> nearly as effective, for example a router (IS in ISO parlance)
> nominally has no use for transport protocols. I would recommend to
> ISO designers to add a mandatory echo response at as low a level as
> possible in the architecture. If the source routing trick does this,
> and is a mandatory capability of ISO 8473, great. I would then ask
> the implementers to provide the necessary user program.

No, partial source routing is NOT mandatory in ISO 8473. I admit,
I knew this when I suggested it, but I did it anyway.

However, from the responses I have seen on this issue, a lot of
people think ICMP ECHO is important.

We in X3S3.3 would like to be obliging, but are a little uneasy of
putting in an all purpose ping without understanding how it will be
used. A lot of people may be using ECHO for things when some other
function may do more for that thing. Since we are just now defining
management functions for the network and transport layers, we are in
a good position to provide a lot more than just pings.

I would like to get some feedback from all those dirty-fingernailed
pingers out there.

What EXACTLY do you use ICMP ECHO for?
Is there a better way to do what you want other than ICMP ECHO, but
you are using ICMP ECHO because it is the only thing available?
Are there things (management-wise) that you wish you could do,
but there is currently nothing standardized to do it with.

Of course, any other random comments are welcome.

> (But enough, this discussion really belongs on the ISO mailing
> list, see the CC: address...)

Yes and no. While tcp-ip is obviously not going to go away, there
is no question (at least in my mind) that tp4-ip is on the way. If
we (the ISO designers) don't get feedback from you (the experienced
tcp-ip designers) on these issues, then the ISO mailing list will
be nothing but a repeat of the tcp-ip mailing list, but delayed
5 or 10 years. I think a lot of things belong on both lists.

While on the ICMP topic, I'd like to bring up another tidbit......
In addition to an error message which is just like SOURCE QUENCH,
there is a thing in ISO-IP called the congestion experienced bit.
It is a bandwidth free way of indicating to transport machines that
your congestion is getting up there, but not to the point where
packets are being thrown away. This is how DEC does it, and it
seems to work for them.

Now the catches. One, its optional. However, optional doesn't
have to mean don't do it. It is groups like COS
(Corporation for Open Systems), the NBS-ISO Workshop, and
GOSIP (or whoever is behind it) that ultimately decide these things.
Two, what a transport does when it receives such a bit is not
standardized (just like SOURCE QUENCH), nor is it standardized
when the bit gets set. Again, COS, NBS, etc., are the places to
fight those battles.

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



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