At 12:54 PM 7/19/00, Ruslan S Tchinyakov wrote:
>Packets are counted to be deferred are due to
>15 successive collisions to happen after first send attempt-
>the CSMA/CD algorythm version used propose the cut of the back off
>algorythm on the 16th attempt (first 10 attempts the timeout (ralli- the RND
>function multiplier) is doubled each time-
>up to 2^10=1024 times initial, then 5 attempts fixed- then drop the packet
>(s)- count them as deferred
>and go to start)- so this implies some not well-uderstood by many readers
>Ethernet limitations-
>such as summary number of 1024 nodes in collision domain and so on.
>
>
>Ruslan Tchinyakov,
>CCNP+Security, CCDP, MCSE
Except, that's not what Cisco means by deferred. I think Cisco counts every
attempt to send that must be deferred because of existing traffic.
Here is what Cisco documentation says: "deferred: Deferred indicates that
the chip had to defer while ready to transmit a frame because the carrier
was asserted."
This means that it's kind of a useless statistic since deferring because
the medium is already in use is absolutely normal on a shared and/or
half-duplex Ethernet. The threshold where it would be considered abnormal
completely depends on the number of stations and their traffic patterns,
which is not easy to measure or predict on a busy, shared Ethernet.
(Luckily, we don't have that many busy, shared Ethernets any more.)
Priscilla
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Priscilla Oppenheimer
http://www.priscilla.com
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