Re: controlling IP "type of service"


Mills@UDEL.EDU
Sat, 14 May 88 16:34:01 EDT


Vint,

Verily in an FB(n) system dudes at higher priority levels can freeze
out dudes at lower priority levels if the volume of traffic at the
higher levels is sufficiently intense. There is now doubt that this
occasionally occurs when the NSFNET Backbone is sore abused by certain
4.2bsd systems that have not upgraded to 4.3bsd with the Jacobson/Karels
pollution controls (point made - I have not yet found a way to reliably
identify 4.2bsd abusers and stamp their passports with priority zilch).
While the freezees can shiver in the queues as the hotrods whiz by,
they can't freeze for longer than their TTL, for most systems not
over thirty seconds and for no systems longer than about four minutes.
What usually happens is that, a packet below the eutectic can't live
more than a few seconds before being preempted anyway. Such is live
in the present 56-kbps world.

Fancier schemes can readily be proposed to improve fairness with FB(n)
systems, many of which were first proposed in the CTSS days when
timesharing was losing its hyphenation. In context of six weeks the
existing 56-kbps backbone is to live before being retired hy the
new 1.5-Mbps backbone, there is small chance that these schemes will
be implemented. There may be at least a month before the new backbone
will have to face the same problems.

Dave



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