[e2e] Simple Question on TCP Window Size

Eric A. Hall ehall at ehsco.com
Wed May 9 07:13:50 PDT 2001

> I think most UDP flows (as opposed to short duration exchanges like
> DNS) would benefit from using ECN and RED information.

Actually, short flows like DNS can benefit from the information if they
are designed to make weighted decisions. For example, DNS resolving
servers that understand the concept of preferred servers will weight the
preferred servers for remote queries according to parameters like
time-to-resolve. Incorporating congestion information as another metric
into this decision is certainly feasible.

This isn't even far-fetched, but it would be a feature rather than a
baseline. As it stands now, some DNS systems use ICMP Destination
Unreachable messages to short-circuit query timers, while others do not.
It's not a stretch to imagine that those servers which already implement
these types of features can use any available feedback, and that would
include ECN (although SQ would be faster and more explicit; some messages
would provide greater weights than others, which would provide more
appropriate adjustments faster, such as responding to immediate critical
congestion with an immediate change in preference or responding to subtle
changes with a minor preference tweak).

Eric A. Hall                                        http://www.ehsco.com/
Internet Core Protocols          http://www.oreilly.com/catalog/coreprot/

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