Lucent Technologies Cajun P220, Operation Manual

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Analyzing Network Performance Using RMON and Ethernet Statistics (Layer 2 & Layer 3)
Cajun P550/P220 Switch Operation Guide 17 - 5
Jabbers Jabbers indicate that devices on the
networks are sending improper
electrical signals. Because Ethernet
uses electrical signalling to
determine whether or not it is okay
to transmit, a jabber condition can
halt all traffic on a segment. Possible causes:
• Bad network interface card
• Repeater network with looped
traffic
Possible actions (respectively):
• Replace network interface card.
• Rewire network to remove the
loop.
Collisions
(half-duplex
links only)
Counts number of times that
packets have collided on the
network. Collisions increase as
network use of shared segments
increases. Therefore, if the collision
rate increases without an increase
of network use, it might indicate a
problem. Guidelines for appropriate
collision rates are:
• 10 percent: Normal collision
rate for shared Ethernet
segment.
• 30 percent: Collisions begin to
interfere with performance.
• 70 percent: Practical limit for
network to remain
functioning.
A full-duplex link should not show
collision activity.
In a switched network, collisions
should be rare, unless your
switched segments attach to
multiple ends stations (a perfectly
legal configuration option).
Possible causes:
• Busy network
• Broken adapter (not listening
before broadcasting)
• Network loop
Possible actions (respectively):
• If you have multiple stations on
a switch segment, reconfigure
network into segments with
fewer stations.
• Isolate each adapter to see if
the problem ceases.
• Activate spanning tree to
resolve loops automatically.
• Ensure that there are no
connections to the same
station where both
connections are
simultaneously active.
Table 17-1. Interpreting Ethernet Interface Statistics (Continued)
Statistic Indicates Actions