38 Given a scenario, troubleshoot common connectivity issues and select an appropriate solution.

Connectivity issues are much more common than infrastructure and wiring problems. Wiring issues are not easy to troubleshoot and hence require a careful and a methodical approach while troubleshooting. Troubleshooting wiring problems is always not a pocket friendly issue. Wiring issues concern the cable in a network. To begin with:

- Find out the kind of cable that has been used in the network;

- Find out where the wiring has been used.

These are important to ascertain, as the problem could be as slight as a wrong cable type being used in an environment for which it was not designed. The kind of cable that has been used is a question, which is easy to determine. The cables are stamped with their complete specifications. It is important to find out where the cable has been used and the surrounding environment. Every cable type has its own set of characteristics which make it suitable or unsuitable for particular surroundings. Some of the problems that can be associated with wiring are:

Cross Talk: Coaxial cables, UTP are prone to cross talk. Cross Talk is the mixing up of signals over two different lines. This problem is faced when copper based wires run close to each other. Shielding can help to reduce cross talk and wires running to close to each other should be avoided.

Near-End Cross Talk (NEXT): Interference encountered between adjacent wire pairs within a twisted pair cable in known as NEXT. It is experienced at the near end of the link. Near end of the link is the link that is closest to the place where the data signal is originating. In this a part of the signal that is going out is coupled back into the signal that is being received.

Far-End Cross Talk (FEXT): This problem is encountered when a station at the receiving end overhears a data signal that is sent by a transmitting station which is at the other end of the transmission line. The interference is identified through a wire pair through an adjacent pair at the end where the signal is being received.

Electromagnetic Interference (EMI): This factor reduces the strength of the signal considerably. It has the potential of completely corrupting the signal. This problem is encountered when cables run close to office fixtures like monitors, electrical lightning fixtures using fluorescent lights, microwaves. Any device that creates an electromagnetic field has the potential of causing EMI in the wiring running close to it. In case it is inevitable and the cable has to be run through an electromagnetic field, it is best to use shielded cables or fiber cables.

Attenuation: Data travels in the form of signals and the same weakens as it moves away from the source of origin. Signals can weaken to the extent of becoming unusable. The weakening of signals is known as attenuation. Attenuation is more likely in copper based wires. Signal regenerators have to be used to boost the signal to make it travel distances longer than what has been recommended.

Open Impedance Mismatch (Echo): a single continuous cable or multiple sections of cables may be used for constructing a network. Multiple sections of wires are attached using switches and other hardware devices. Slightest difference in the impendence of the sections of the cable can cause impendence mismatch. Impendence is the opposition that a circuit or a device offers to the flow of a signal. Impendence is measured in Ohms. It is recommended that cable sections with matching impendence should be used.

Shorts: Shorts is the term that is used to refer to the flowing of electrical current from a path which is different from the intended one. This kind of a situation is encountered when the network cables have not been correctly set up. Wires could be touching each other, improperly grounded, bent or mishandled resulting in shorts. Shorts are more commonly in copper based wires.

Collisions: When two or more devices transmit data at the same time a collision occurs. The data that collides becomes corrupted and has to be resent. Recurrent collisions slow down the network which ultimately does not go well with the users of the network. MAC (Media Access Control) techniques can be incorporated to deal with collisions. The most common methods used for dealing with collisions are:

- Collision Sense Multiple Access (CSMA)/ Collision Detection (CD) which is used with wired Ethernet networks and

- Collision Sense Multiple Access (CSMA)/ Collision Avoidance (CD) which is used with 802.11 wireless networks.

Ethernet networks slow with the addition of devices on the network. The Ethernet systems need improvements in terms of replacing older hubs with newer ones or even switches as they allow for segmentation of the network into smaller divisions.