DescriptionWireless network is slow
ScopeKB ARTICLE
TYPE: Troubleshooting
RELATED
SOFTWARE VERSIONS: All
RELATED
PRODUCT TYPES: All
KEYWORDS:
slow, retries, low data rate,
congestion
SolutionIn general, the
complaint will be slow performance – download speeds may be low,
application timeouts may occur, or general sluggishness may be
reported.
- If the performance problems
began while the user was moving, it is possible that roaming failed.
Examine the client’s current signal strength and data rate. If
they are low, compare the user’s physical location with the
location of the currently associated AP. This is sometimes caused by an
issue known as “client stickiness” – the tendency
for a client to maintain an existing association and ignore closer APs
even when signal strength has significantly degraded. Ideally,
predeployment testing will identify client NICs and drivers that exhibit
this problem so that they can be excluded from the
deployment.
- If RSSI – also known as signal strength
is low (below 20), the client has poor signal strength to the nearest
AP. This may indicate a roaming failure, described
above.
- If “transmit retries” is
high, the client is sending frames that are not being acknowledged by
the AP. The client is then forced to retransmit these frames, reducing
performance. The cause may be interference or low signal
strength.
- If “receive retries”
is high, the AP is sending frames that are not being acknowledged by the
client. The AP is then forced to retransmit these frames, reducing
performance. The cause may be interference or low signal
strength.
- If the transmit or receive data rate is
low, it indicates that the client or AP’s rate adaptation
algorithm has detected errors at higher data rates and is forcing a
lower rate. This could indicate interference or low signal
strength.
- If signal strength is high, retry rate is
high, and data rate is low,the cause may be localized interference.
These symptoms indicate a client that is close to the AP with good
signal strength, but with poor communication between the AP and client.
Examine the Events tab in the GUI and look for any indications of
detected interference.
- If the above parameters are
within acceptable ranges, but throughput is still low, it may indicate a
congested AP. Perform activity monitoring on the entire AP rather than
on the individual client to examine how much bandwidth is being consumed
on the AP. If there are too many clients connected to a given AP,
performance may be increased by reducing the maximum number of clients
allowed on the AP.
There may be congestion
on the wired portion of the network. Examine the wired network using
traditional tools such as “ping” and
“traceroute” or using sniffer
software.
Perform a wireless packet capture
to view any anomalous conditions in the area covered by the
AP.
