Date: Fri, 23 May 2003 12:50:30 +0200 From: jeremie le-hen <le-hen_j@epita.fr> To: ipfw@freebsd.org Subject: Understanding queue size Message-ID: <20030523105030.GA24992@carpediem.epita.fr>
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Hi,
ipfw(8) manual page, section "TRAFFIC SHAPER (DUMMYNET) CONFIGURATION" tells:
queue {slots | sizeKbytes}
Queue size, in slots or KBytes. Default value is 50 slots, which
is the typical queue size for Ethernet devices. Note that for slow
speed links you should keep the queue size short or your traffic
might be affected by a significant queueing delay. E.g., 50 max-
sized ethernet packets (1500 bytes) mean 600Kbit or 20s of queue on
a 30Kbit/s pipe. Even worse effect can result if you get packets
from an interface with a much larger MTU, e.g. the loopback inter-
face with its 16KB packets.
I understand that if the queue size is too large, then it will imply large
delays. But what if the queue is too short ? Does anyone can point me a
detailed document which talks about queues ? Or maybe it exists a simple
general rule explaining all this stuff...
Regards,
--
Jeremie aka TtZ/TataZ
jeremie.le-hen@epita.fr
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