Msft 2578: Network Essentials

There are two main types of twisted-pair wiring used for data communications: unshielded twisted-pair (UTP) and shielded twisted-pair (STP). Both types can be used in a star topology. UTP and STP cables contain eight copper conductors arranged in four pairs, although generally only two pairs are used for transmission and reception. UTP and STP cables use RJ-45 connectors to connect end systems to hubs, patch panels, and wall plates. RG-8 and RG-58 coaxial cable can only be used in a linear bus topology. Fiber-optic cable can be used in a star topology, but it uses either glass or plastic conductors and doesn’t use RJ-45 connectors.

The star topology using twisted-pair cable fulfills all the client’s requirements. It supports a small number of users, and twisted-pair cable is rated for 100 Mbps. Adding and removing systems is very easy. To add a system, you simply connect the system to the hub, using a prefabricated unshielded twisted-pair (UTP) patch cable with an RJ-45 connector. If a cable or connector fails, it doesn’t affect the other systems. This makes the star topology easier to troubleshoot than other topologies. Twisted-pair cable rated as Category 5 (Cat5) or higher can handle a data transfer rate of 100 Mbps. Twisted-pair cable isn’t very expensive. The bus topology that uses coaxial cable doesn’t run at 100 Mbps and is harder to troubleshoot. A cable failure in a bus will cause the network to go down. The full mesh topology with fiber-optic cable is extremely expensive, so it doesn’t meet the client’s criteria. Also, the full mesh topology can’t be implemented for end user connections on a local area network (LAN). The ring topology with twisted-pair cable doesn’t typically support 100 Mbps. In a true ring topology, a single failure will bring down the entire network.

A crimper or crimping tool is a jawed device that has a set of dies in it. You use a crimper to squeeze the two halves of an RJ-45 or RJ-11 connector together, with the wires inside securing the connector to the cable. A splicing tool is used to splice two cable segments together. There is no tool called a pigtail or a patch.

You use a punchdown block tool to connect the ends of bulk cable runs to jacks in wall plates and patch panels. A crimper or crimping tool is a jawed device that enables you to squeeze the two halves of an RJ-45 or RJ-11 connector together, securing the connector to the cable. You use a splicing tool to splice two cable segments together. There is no tool called a pigtail.

The twists prevent the signals on the different wires from interfering with each other (which is called crosstalk) and also provide resistance to outside interference. The twists in twisted-pair cabling have no control over collisions. The twists can’t completely eliminate the effects of EMI. Twists have nothing to do with the bend radius allowance for the cable.

The star topology requires a central device known as a hub or concentrator. Each end system is directly connected to the hub by twisted-pair patch cables. The hub broadcasts a transmitted signal out all ports except the one the signal was received through. The bus topology does not use a central device or twisted-pair cabling. The full mesh topology does not use a central device. Wireless networks do not use twisted-pair cabling. In a ring topology signals are sent in one direction only.

Either CAT5e or CAT6 cable will provide the current 100-Mbps data rate with a migration path for 1,000 Mbps in the future. The backbone cabling connecting the two LANs needs to be fiber-optic, because it exceeds the distance limitations of twisted-pair and coaxial cable. CAT3 cable runs at 100 Mbps over four twisted-pairs; however, it does not run at 1,000 Mbps.

LANs typically use the bus, star, or ring topology. Mesh networks are typically used by wide area networks (WANs).

Because the company has few employees, it is in a single location, and the client is concerned with costs, the best solution is to use a star topology with prefabricated twisted-pair cabling and an external installation method. The star topology uses a central hub device. Two hubs can be used, one in each room, to connect computers to the network. Prefabricated twisted-pair cabling, which contains the connectors and is available in predetermined lengths, will keep costs to a minimum. Because the employees are all located in the same building and share a common wall and door, and because the ceiling is a drop ceiling with tiles, the external installation method is recommended. You could use a ring topology, but not with fiber-optic cable implemented as an internal installation. Fiber-optic cable supports data rates of 100 Mbps, but it is more difficult to install, is very expensive, and isn’t suitable for this type of installation. Fiber-optic cable is typically used to add distance to a network and overcome problems with electromagnetic interference (EMI). Internal installation methods are most often used in large networks, where end systems are geographically distant, such as different buildings and floors. Internal installations use a combination of bulk cable with no connectors and prefabricated cable. They also include longer, more complex cabling routes that run from a hub connected to a patch panel through places such as walls, ceilings, and air ducts to a face plate and finally to an end system. The full mesh topology is used for wide area networks (WANs) and requires that all network devices be directly attached to each other. It is extremely expensive and not suited for small installations.

The thin Ethernet LAN is the network most endangered by the cable break. If a bus network is severed, all the workstations on it are affected because the network is no longer terminated at one end. The Fast Ethernet network uses a star topology, which means that only the one computer using the severed cable is disconnected from the network. An FDDI double ring network can survive a single cable break without any workstations being affected.

The best solution is to install a fiber-optic FDDI network configured in a double ring topology. FDDI runs at 100 Mbps, and the double ring has dual counter rotating rings for fault tolerance (providing a backup path) and isn’t subject to collisions. It is also immune to electromagnetic interference (EMI), which makes it an ideal topology to use on the floor of a noisy manufacturing plant. Fast Ethernet configured in a star topology, using twisted-pair cabling (CAT5e or CAT6) doesn’t meet the needs of the network because it doesn’t prevent collisions, it doesn’t provide a backup path, and it is subject to EMI. Token Ring does provide a backup path, is deterministic, and uses STP cabling (type 1 and 6), but it is susceptible to EMI and would not do well in this scenario. A linear bus topology offers no backup path and, therefore, doesn’t meet the requirements.

The best solution is to keep the existing CAT3 cabling, which supports 100 Mbps over four twisted-pairs (100Base-T4). In fact, this is the only solution because your client does not have the budget to change the cabling installation. The Fast Ethernet standard for 100 Mbps over CAT3 twisted-pair is 100Base-T4 (four pairs) not TX (two-pair CAT5, 5e, or 6) or FX (fiber). CAT2 cabling doesn’t support 100 Mbps.

The cable type used for thick Ethernet segments is RG-8. RG-58 is used exclusively on thin Ethernet segments. RJ-45 is a connector type used in twisted-pair cabling for data networks. RJ-11 is a connector type used in twisted-pair cabling for telecommunications networks.

ST, SC, Fiber LC, and MT-RJ are all connectors used with fiber-optic cables. F-type connectors are used with coaxial cables.

The cable type and connector used to attach a television set to a CATV network is a coaxial cable with a screw-on F-type connector. Although CATV networks typically use fiber-optic cables and ST connectors for outdoor connections, they do not use fiber for internal connections to television sets. Coaxial cables with BNC connectors are most commonly used for thin Ethernet LANs, not CATV network connections. Twisted-pair cables and RJ-45 connectors are used for Ethernet LANs and telephone networks, but not CATV networks. AUI cables and vampire tap connectors are used for thick Ethernet networks.

CAT3 cable was originally rated for use in voice-grade telephone networks but has since been certified for use in data networks. CAT3 cable can support data transfer rates from 4 Mbps up to 100 Mbps (100Base-T4 and 100VG-Any LAN). Although this type of cable can run at 100 Mbps, it is seldom used, and it isn’t recommended for transfer rates greater than 10 Mbps. CAT2 is used for telephone networks, miniframe and mainframe connections, and older data network architectures such as ARCNet and LocalTalk. CAT4 cable can be used in Token Ring networks that offer 16-Mbps data rates. CAT5 cable is the primary cable standard for data rates up to 100 Mbps. CAT5e is rated for data rates up to 1000 Mbps, as on Gigabit Ethernet networks.

Multimode fiber-optic cable best meets the corporation’s needs. Fiber-optic cable supports the required 100-Mbps data rate and can connect networks that are more than 1,000 meters apart. Fiber-optic cable is immune to EMI. Although both multimode and singlemode fiber would meet the corporation’s general needs, multimode is best in this scenario because it is less expensive than singlemode fiber. Twisted-pair wiring (STP or UTP) meets the data rate and cost requirements but does not support connections longer than 100 meters. Thin coaxial cable does not support the data rate or distances longer than 185 meters.

A thin Ethernet network runs at 10 Mbps and can support 20 workstations, achieving the primary goal. However, thin Ethernet uses copper cable, which is susceptible to EMI, and it uses a bus topology, which is not tolerant of a cable break. Therefore, the solution doesn’t achieve either of the secondary goals.

Most implementations of the ring topology include a central device similar to a hub. All devices are directly connected to the hub in a physical star configuration. However, the logical signal flow is still a ring. The bus topology specifies a linear cabling system. A full mesh network doesn’t use a central device; all devices are directly connected to each other. There is no topology type called full star.