Network Failure document (Supporting case study)
Connectivity
There are many network/computer issues that may rise up in a shop environment. These issues may range from network slowdowns to loss of data. It is very important to have a cable company test the network cabling and switches on an annual basis. You also need to test for a dual ground on the electrical circuit, and any possible interference coming through the cabling. Interference can be caused by a number of sources such as cable being to close to florescent lights, electrical wiring, and more. 9 out of 10 network problems we have run across comes down to hardware failure. Other issues are network configuration or Operating system failure. For example, welding equipment has been known to causing noise interference so severe, that data is destroyed and computers cannot see each other on the network. Attenuation or network cable length of run beyond the capability of the cable creates signal degradation and is a common cause with network failure. Once the hardware and network architecture is properly setup and functional, the base for any system will manageable.
Network Connectivity
This will cover several reasons
why a network may have trouble. One
such reason for poor network stability is interference. Interference can be caused by many sources,
and the following describes different scenarios.
A network is a setup of multiple computer systems that are connected together using a medium of some sort. The most commonly used medium for a Local Area Network (LAN) is CAT5 cable that is made of a shielded set of four twisted pair wires for a total of eight wires. Connecting multiple computers together makes a circuit for electrical current to pass through. Data is sent from a computer as a digital signal using 3 to 5 volts. For example, 0 equals 0 volts and 1 equals 3-5 volts so a signal that would come across as 00010011 would actually be sent in potential (voltage) as 0,0,0,3,0,0,3,3. In a perfect scenario, there will be no outside voltage to disrupt the flow of this digital current.
The cabling is the backbone of the network. Without properly working network cabling,
your network will fail. A cable can go
bad several ways. For example, the
wires can break within the casing causing the circuit to cease. Different network cabling types also have
different distance ranges. The longer
the cable is, the more the signal degrades.
A cable run cannot exceed the cable run without a device like a
repeater.
A ground in an electrical circuit is a common return path that is the
zero voltage reference level for the equipment or system, and usually is
connected into the earth. Grounding is
very important when dealing with electricity, because it allows the buildup of
electricity to dissipate. Without a
proper ground the current will become unstable and may cause breakers to
activate. When properly installed, the
low-resistance path provided by the safety ground wire offers sufficiently low
resistance and sufficient current-carrying capacity to prevent the buildup of
Hazardous high voltages. A single power
outlet or light socket with an exposed or damaged wire can cause the ground to
fail.
Multiple grounds
Many of the larger buildings require multiple
grounds, and multi-building sites also require more than one ground. Multiple grounds are problematic do to the
fact that the potential is almost never the same. If computer systems are located on separate grounds and are
connected through a network, a circuit is formed out of the network wire. This creates multiple grounds on the same
circuit, which will make the current from the source with negative potential
flow to the ground with positive potential.
This can disrupt a digital signal that would normally be 00010011
(0,0,0,3,0,0,3,3 volts) to then become 01011111 (2,4,1,6,5,4,5,6 volts). Unfortunately, a signal that is distorted in
this way may disconnect a system from a network, destroy data, or even damage
computer hardware.
Signal Interference
Another cause of network disruption caused by
electrical interference can be attributed to equipment that produces high
frequencies such as fluorescent lights, high frequency welders, generators,
anything that is phase 3, etc… There is
always network interference (noise) going through the network cable, but the
noise to signal ratio is what is important.
Some contractors and electricians do not take this into consideration
when wiring a building. When installing
network cable, it is important to hire a network engineer or a cabling company
to get the job done right the first time.
Troubleshooting tips
One way that can help locate a
problem causing network node is using a software server called telnet. Windows server does have a telnet server integrated
into the operating system that is great to use.:12 span>Disable the connection timeout on the telnet server that you are
going to use for this test. Then
connect all of your workstations to the server through the telnet client
already installed on your system. Leave
these workstations connected to the server for several days. Note the computers that have disconnected
from the server. If only a couple
telnet sessions disconnected, then you may have pinpointed the network segments
(computer, network card, cable, switch) that are causing the network
problems.
Log in as necessary
Jeremy Martin CISSP, ISSAP, CCNA, Network+, A+
Director of Communications
PLUSS Corporation
1-800-835-9609
www.pluss.net