Lucent Technologies P550 manual 281

Analyzing Network Performance Using RMON and Ethernet Statistics (Layer 2 & Layer 3)

Table 17-1.Interpreting Ethernet Interface Statistics (Continued)

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

Cajun P550/P220 Switch Operation Guide 17-5