Network Performance
Tips to solve network latency issues
Proactive monitoring can help locate
and correct slowdowns.
by Chris Bloom
The
network is running all kinds of
applications, from single-tier applications
like e-mail to multitier Web-based databases
or complex voice-over-Internet-protocol
(VoIP) applications. The enterprise IT
department does not necessarily have control
over all of the applications, because some
of these applications are running on
networks outside of the enterprise and some
may be outsourced. Pinpointing and
correcting slowdowns, therefore, can be a
challenge.
Monitoring tools can help locate and
solve problems with latency. A
quality-of-service (QoS) monitoring solution
can provide the data needed to prove that
the network is performing poorly or
applications are slow. The monitoring
solution can collect data 24/7 and send
alarms automatically to notify
administrators when something on the network
is not performing as expected. The first
step is to determine if the latency is
coming from the network or the application.
Network latency is the amount of time it
takes for an application to make a request
and the server to respond with an
acknowledgement (a packet message used in
the transmission control protocol to
acknowledge receipt of a packet).
Application latency is the amount of time
needed for the application to process the
request and send a response containing real
data.
Most network-monitoring products provide
some sort of latency-monitoring features,
typically either one or the other, not both.
Ideally, these measurements can be graphed
together over time, making clear whether the
problem lies with the network or the
application. Comparing the measurements of
the two types of latency over time and
seeing the differences can provide
information that might have otherwise been
overlooked.
Graphing latency over time helps to
identify patterns and anomalies that deserve
closer attention. Latency monitoring can
help correlate areas of latency with other
relevant statistics, as well as the actual
packets that occurred during that time. This
type of high-resolution forensic analysis
can help to detect latency problems at the
highest level and drill down quickly for
closer inspection.
Being able to see graphs over time and
correlate the latency is important, as
latency patterns allow the administrator to
compare the patterns to other events on the
network, and determine the root cause of the
problem. Latency monitors can include a
feature that sets thresholds on latency, so
alarms will go off when normal conditions
are exceeded. The administrator can be made
aware of excessive latency before
applications on the network start dropping
packets, allowing him to make necessary
adjustments to the network proactively. This
type of proactive latency monitoring allows
the administrator to detect and correct
problems in the network and applications
before users notice a slowdown.
Chris Bloom is a developer evangelist
at
WildPackets, Walnut Creek, Calif.
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