Re: [Trigtran] Why TRIGTRAN isn't ICMP Source Quench/Why TRIGTRAN isn't ECN

Included message from "Spencer Dawkins" <sdawkins@cynetanetworks.com>:

>----
>ICMP Source Quench
>------------------

....

>- ICMP Source Quench affected only packets sent from the host generating the
>"over the top" packet, so did not provide a fair mechanism for hosts sharing
>overcommitted network paths, and 
>
>- ICMP Source Quench added (reverse-direction) packets to the network during
>congestion events, and used router memory and processing power to construct
>and send ICMP Source Quenches during congestion events.
>
>The overwhelming problem with ICMP Source Quench wasn't that it required
>gateways to send a "trigger" to hosts - it had problems with unfairness and
>inefficiency. Since the specifications omitted critical details and didn't
>require this functionality, hosts were forced to add end-to-end congestion
>avoidance at the transport layer, anyway.

I think that if the decision was to be made today, the simple reason
of security would be enough to ignore ICMP source quench message
altogether.  I know that some TCP stacks used to treat ICMP source
quench message as a segment drop, similar to an ECN signal.  This
means that a very simple DoS can be done to those hosts which respond
to such ICMP messages, even if its response follows the same behavior
as ECN signals.  This can be applied to triggers.  One reason
why ECN is better is that it is end2end.

As a matter of fact, ICMP message is probably the simpliest DoS tool
out there.  If a host is to process every ICMP messages, at least up
to the TCP level, it will not survive in today's Internet.  Will
trigger become another such tool?

>This experience isn't terrically relevant to TRIGTRAN, because
>recommendations have shifted from MAY to SHOULD NOT - hardly an overwhelming
>push to deployment!

If trigger was to be done as advisory signal, it would probably be
a MAY in the RFC.  Will you think that it will follow the same fate?

>----

							K. Poon.
_______________________________________________
Trigtran mailing list
Trigtran@ietf.org
https://www1.ietf.org/mailman/listinfo/trigtran