Information Technology Reference
In-Depth Information
A LAN wiring system is a dynamic entity in many ways, changing and growing
much like a living thing. If the LAN operating system is like the lifeblood of your
network, the signal wiring certainly is like the nervous system, carrying important
messages from point to point. LAN wiring must be monitored and tracked, so that
you can constantly know the status of your interconnections.
LAN wiring systems are not truly passive systems. They are active in the sense
that they can change characteristics over time and can disrupt the LAN if they fail.
When a failure occurs, you will need to make quick repairs. How well you are able
to respond to a cable problem depends on the methods available to you to isolate
the problem and find the offending cable system component. Proper documentation
of your wiring will assist you in your installation and troubleshooting efforts. This
is the essence of monitoring and administration.
Monitoring of a cable system can be accomplished either directly or indirectly. For
most installed LAN systems, the networking equipment (servers and worksta-
tions) can do a part of the job indirectly. We call this
indirect
monitoring, because
it is a part of the normal operations of the connected systems, which sense the sta-
tus of the network links indirectly. If a workstation cannot connect to a server, it
may mean that there is a connectivity problem, such as a bad cable or other wiring
component.
Unfortunately, indirect monitoring of the Channel may indicate a communica-
tions problem even when the cable connectivity is fine. For example, a bad work-
station network interface or a software problem at the workstation, switch, or
server would appear as a network communication problem, even though the cabling
is good.
Direct
monitoring uses the capabilities of the hubs, patches, or network inter-
face cards (NICs) to directly monitor the cable link. This type of monitoring senses
the condition of a cable and allows direct control and/or testing of the Channel.
Direct monitoring may be done on either a local or a remote basis. Local monitor-
ing simply uses the built-in status indicators on hubs and NICs. To monitor link sta-
tus, one simply looks at the LED indicators on the devices. Of course, this assumes
that the devices you are using have indicator lights.
Remote monitoring uses intelligence built into the hubs or other network
devices to report status to a monitoring station. Remote monitoring can use stan-
dard network monitoring software, such as SNMP, described later in this chapter.
Remote monitoring is rather new and offers an exciting new view of the LAN wiring
as a separable entity. It is, unfortunately, still somewhat too expensive to implement
