Guest
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 Posted:
Tue Nov 01, 2005 5:20 pm Post subject:
Official - Collisions are errors - Nokia, Cisco |
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Hello,
Clearly no one can help however I feel
that some of you may be interested in the
following.
I have recently run into two devices that appear
to report ethernet collisions as interface
output errors.
1.
Nokia firewall IPSO 3.8
2.
Some Cisco switch or router (sorry did not
make a note of it at the time).
In the nokia case I had no immediate access to the
device connected to the Nokia via a point
to point link.
The Nokia was set to FD and was reporting Input errors
I set it to HD and then got output errors.
All via Voyager GUI.
Then I noticed that netstat -ni
showed that
number of collisions = number of errors.
snmp mibs (interface, transmission.dot3)
agreed that there were no late collisions.
Setting the Nokia to HD reduced the rate of
lost packets by a factor of about 100.
i.e. eliminated them.
The Cisco similarly reported the same number of
collisions as output errors, no late collisions
and I had confidence that the link was good for
reasons that I now forget.
I conclude:-
The two poisons, namely 'Collisions Are
Bad, Very Bad' and 'Half Duplex is Useless,
Completely Useless' have reached new levels
of power and are irresistable.
The only fix (other than re-education, which
can never succeed in this matter) is to
banish HD Ethernet from your network.
This seems a good argument for GBE
(or ATM:) to the desk.
Is in not amazing that two of the biggest
mistakes (and indeed they may be the only
significant errors) in the Ethernet (802.3)
standards appear to have been social errors
and not technical errors.
I refer of course to.
a) The selection of the term collision.
b) The Duplex auto-negotiation behaviour.
The latter has resulted in I guess
millions and millions of functionaly
impaired links due to the social
inevitability that 'FD is best' and
must be hand configured by any concientions
system admin while they simultaneously
don't bother to ensure that all devices
are so configured. |
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James Knott
Guest
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| Posted:
Wed Nov 02, 2005 8:07 am Post subject:
Re: Official - Collisions are errors - Nokia, Cisco |
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anybody43@hotmail.com wrote:
| Quote: | I conclude:-
The two poisons, namely 'Collisions Are
Bad, Very Bad' and 'Half Duplex is Useless,
Completely Useless' have reached new levels
of power and are irresistable.
|
Collisions within the first 512 bits are not errors, they're collisions and
entirely normal. Collisions occuring later are due to the failure of a
NIC, to detect traffic on the wire. |
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