6 Given a scenario, differentiate and implement appropriate wiring standards (568A, 568B, Straight vs. crossover, Rollover, Loopback)

Wiring Standards: 568A and 568B Wiring Standards

The Electronics Industry Association (EIA) and The Telecommunications Industry Association (TIA) have specified 568A and 568B as the telecommunications standards. The "568" refers to the order in which the wires within the Category 5 cable are terminated and attached to the connector. The pin arrangements for the RJ connectors on UTP or STP cables are specified in the se standards.

The signal in both the standards is the same. In an Ethernet network both can be used for patch cords. Custom length cables need to be made at times and at such instances it becomes necessary to know the order in which the individual wires are to be attached to the connector. Both the standards are similar with a difference in the order in which the pins are terminated. Pin numbers are read from left to right with the face of the connector tab down. The figure given below illustrates the pin number assignments for both the standards.

568A Pin Assignment 568B Pin Assignment

Crossover Cable Vs. Straight Cable: Hubs and Switches can be interconnected using either crossover or straight through cable. The difference between the two is that in crossover cable, two sets of wires are crossed and in a straight through cable all the wires run straight through. For example, in a cross over cable wires 1 and 3 are crossed over with wires 2 and 6. Figures 1.23 and 1.24 illustrate the differences between the two cable types.

Figure 22: Pin Outs for a Straight through Twisted Pair Cable

Figure 21: Pin Assignments (568A and 568B Standards)

Figure 23: Pin Outs for a Cross over Twisted Pair Cable

Roll over and Loopback Cables: The rollover is proprietary of Cisco and is not usable on any other equipment. It looks like an Ethernet UTP cable and is used to interconnect a computer to a router or a switch console port. It has eight wires and RJ connectors on each end connected to the router and the computer port. As far as the arrangement of the pin outs is concerned, pin 1 on the end of the rollover cable is connected to pin 8 at the other end of the cable; pin 2 with pin 7, pin 3 with pin 6 and so on. The ends are reversed following the same pattern. Once connection is made between the PC and the Cisco terminal, the Cisco equipment is accessible from the computer system. This is made possible by programs such as Hyper Terminal.

Also known as loopback plug, it is used in testing, isolating network problems and trouble shooting. The link light on a device can be made to come in if the set up is made correctly. It is a fast and a cost effective method for checking cabling problems. The outgoing data is signaled back to the system by using a loopback plug. The system is made to believe that it is sending as well as receiving data. It uses UTP cable and RJ-45 connectors.