+ Transmission Media

+ Local Area Networks LANs consist of Transmission media and network nodes. Transmission media is a pathway that carries the information from sender to receiver. We use different types of cables or waves to transmit data.

+ Types of Transmission Media Transmission media is broadly classified into two groups. 1. Wired or Guided Media or Bound Transmission Media 2. Wireless or Unguided Media or Unbound Transmission Media

+ Wired or Guided Media or Bound Transmission Media Bound transmission media are the cables that are tangible or have physical existence and are limited by the physical geography. Popular bound transmission media in use are twisted pair cable, co-axial cable and fiber optical cable. Each of them has its own characteristics like transmission speed, effect of noise, physical appearance, cost etc.

+ Wireless or Unguided Media or Unbound Transmission Media Unbound transmission media are the ways of transmitting data without using any cables. These media are not bounded by physical geography. This type of transmission is called Wireless communication.. Wireless channels can be divided based on wave frequency Microwave Infrared Laser

+ Microwave Used to send signals between 30m-100m inside buildings, and 100m-300m outside. Microwave can travel through walls or any type of barriers that disallow wired or fixed transmission media. It can be affected by Electromagnetic Interferences and noise. Signals and waves propagate in all the directions around Omnidirectional from (aerial: special device) attached to NIC or any network devices

+ Infrared Can send data through limited area inside the building Infrared have high speed transmission rate between PCs and\or other devices in LAN such as printer. Can NOT go through walls or any barriers. It does NOT affected by noise and interference with any electromagnetic waves. Infrared signals affected by Sun light. Unidirectional, Diffused

+ Laser Can NOT go through walls or barriers or fog or heavy rain. It does NOT affected by noise and Electromagnetic Interference. It affected by Sun Light. Laser signals may curve, bend if affected by high temperature. Laser is Unidirectional.

+ Connectors Hardware pieces connecting wire to network device Every networking medium requires a specific kind of connector The type of connector you use affect the cost of Installing and maintaining network Ease of adding new segments or nodes Technical expertise required to maintain network 9

+ Media Converters Connectors are specific to a particular media type, but that doesn’t prevent one network from using multiple media. Some connectivity devices are designed to accept more than one type of media. If not, we can integrate the two media types by using media converters. Media converter A piece of hardware enabling networks or segments running on different media to interconnect and exchange signals 10

+ 11 Figure 3-15 Copper wire-to-fiber media converter

+ Coaxial Cable Coaxial cable consists of a c entral metal core (often copper) surrounded by: Insulator Braided metal shielding (braiding or shield) Outer cover (sheath or jacket) 12 carries the electromagnetic signal acts as both a shield against noise and a ground for the signal protects the cable from physical damage

+ Coaxial Cable (cont’d.) Because of its shielding, it has high noise resistance to noise Advantage over twisted pair cabling Carry signals farther before amplifier required Disadvantage over twisted pair cabling More expensive Hundreds of specifications Differences between the cable types: shielding and conducting cores which influence their transmission characteristics Each type of coax is suited to a different purpose. All types have been assigned an RG specification number. 13

+ Coaxial Cable (cont’d.) When discussing the size of the conducting core: American Wire Gauge (AWG) size Larger AWG size, smaller wire diameter Data networks usage RG-6 : to deliver broadband cable Internet service and cable TV, particularly over long distances RG-8: 10Base-5 Ethernet (old) RG-58: is more flexible and easier to handle and install, 10Base-2 (old) RG-59: used for relatively short connections, 14

+ Coaxial Cable (cont’d.) The two coaxial cable types commonly used in networks today, RG-6 and RG-59, can terminate with one of two connector types: an F-type connector or a BNC connector 15 Figure 3-17 F-Type connectorFigure 3-18 BNC connector

+ Twisted Pair Cable Twisted pair cable consists of color-coded insulated copper wire pairs Every two wires are twisted around each other to form pairs all the pairs are encased in a plastic sheath The number of pairs in a cable varies, depending on the cable type 16 Figure 3-19 Twisted pair cable

+ Twisted Pair Cable (cont’d.) The more wire pair twists per foot The more resistance the pair to cross talk Higher-quality More expensive twisted pair cable Twist ratio The number of twists per meter or foot High twist ratio Greater attenuation 17

+ Twisted Pair Cable (cont’d.) Because twisted pair is used in such a wide variety of environments and for a variety of purposes, it comes in hundreds of different designs These designs vary in their twist ratio, number of wire pairs, copper grade, shielding type, shielding materials A twisted pair cable may contain from1 to 4200 wire pairs possible Modern networks typically use cables that contain four wire pairs, in which one pair is dedicated to sending data and another pair is dedicated to receiving data Wiring standard specification TIA/EIA 568 Most common twisted pair types Category (cat) 3, 5, 5e, 6, 6a, 7 CAT 5 or higher used in modern LANs 18

+ Twisted Pair Cable (cont’d.) Advantages Relatively inexpensive Flexible Easy installation Spans significant distance before requiring repeater (though not as far as coax). Accommodates several different topologies, although it is most often implemented in star or star-hybrid topologies. Two categories Shielded twisted pair (STP) Unshielded twisted pair (UTP) 19

+ STP (Shielded Twisted Pair) STP (shielded twisted pair) cable consists of twisted wire pairs that are not only Individually insulated but also surrounded by metallic substance shielding (foil) The shielding acts as a barrier to external electromagnetic forces It also contains electrical energy of signals inside May be grounded to enhance its protective effects 20 Figure 3-20 STP cable

+ UTP (Unshielded Twisted Pair) UTP (unshielded twisted pair) cabling consists of one or more insulated wire pairs encased in plastic sheath UTP doesn’t contain additional shielding for the twisted pairs As a result, UTP is both less expensive, less noise resistance than STP 21 Figure 3-21 UTP cable

+ Comparing STP and UTP Throughput STP and UTP can transmit the same rates Cost STP and UTP vary Connector STP and UTP use Registered Jack 45 (RJ 45) Telephone connections use Registered Jack 11 (RJ 11) 22

+ Comparing STP and UTP (cont’d.) Noise immunity STP more noise resistant Size and scalability Maximum segment length for both: 100 meters 23

+ Terminating Twisted Pair Cable Patch cable Relatively short cable ( usually between 3 and 25 feet) Connectors at both ends Proper cable termination techniques Basic requirement for two nodes to communicate Poor terminations: Lead to loss or noise TIA/EIA has specified two different methods of inserting twisted pair wires into RJ-45 plugs TIA/EIA 568A TIA/EIA 568B 24

+ 25 Figure 3-24 TIA/EIA 568A standard terminations Figure 3-25 TIA/EIA 568B standard terminations Functionally, there is no difference between the standards. You only have to be certain that you use the same standard on every RJ-45 plug and jack on your network, so that data is transmitted and received correctly

+ Terminating Twisted Pair Cable (cont’d.) Straight-through cable Terminate RJ-45 plugs at both ends identically following one of the TIA/EIA 568 standards used to connect a workstation to a hub or router Crossover cable Transmit and receive wires on one end reversed to connect two workstations without using a connectivity device or to connect two hubs through their data ports 26 Figure 3-26 RJ-45 terminations on a crossover cable

+ Terminating Twisted Pair Cable (cont’d.) Termination tools Wire cutter Wire stripper Crimping tool After making cables: Verify data transmit and receive 27

+ Fiber-Optic Cable Fiber-optic cable (fiber) One or more glass or plastic fibers at its center (core) Data transmission Pulsing light sent from laser or light-emitting diode (LED) through central fibers Cladding Layer of glass or plastic surrounding fibers Different density from glass or plastic in strands Reflects light back to core in patterns that vary depending on the transmission mode Allows fiber to bend 28

+ Fiber-Optic Cable (cont’d.) Plastic buffer outside cladding Protects cladding and core Opaque to absorb escaping light Surrounded by Kevlar (polymeric fiber) strands to prevent the cable from stretching, and to protect the inner core further Plastic sheath covers Kevlar strands 29 Figure 3-30 A fiber-optic cable

+ Fiber-Optic Cable (cont’d.) Different varieties Based on intended use and manufacturer 30 Figure 3-31 Zipcord fiber-optic patch cable Courtesy Course Technology/Cengage Learning

+ Fiber-Optic Cable (cont’d.) Benefits over copper cabling Extremely high throughput Very high noise resistance Excellent security Able to carry signals for longer distances Industry standard for high-speed networking Drawbacks More expensive than twisted pair cable Requires special equipment to splice 31

+ SMF (Single-Mode Fiber) Consists of narrow core (8-10 microns in diameter) Laser-generated light travels over one path Little reflection Light does not disperse as signal travels Can carry signals many miles: Before repeating required Rarely used for shorter connections Due to cost 32

+ MMF (Multimode Fiber) Contains core with larger diameter than single-mode fiber Common sizes: 50 or 62.5 microns Laser or LED generated light pulses travel at different angles Greater attenuation than single-mode fiber Common uses Cables connecting router to a switch Cables connecting server on network backbone 33

+ Fiber-Optic Converters Required to connect multimode fiber networks to single-mode fiber networks Also fiber- and copper-based parts of a network 34 Figure 3-38 Single-mode to multimode converter Courtesy Omnitron Systems Technology

+ Serial Cables Data transmission style Pulses issued sequentially, not simultaneously Serial transmission method RS-232 Uses DB-9, DB-25, and RJ-45 connectors 35

+ Structured Cabling Cable plant Hardware that makes up the enterprise cabling system Cabling standard TIA/EIA’s joint 568 Commercial Building Wiring Standard Also known as structured cabling Based on hierarchical design 36

37 Figure 3-42 TIA/EIA structured cabling in an enterprise Courtesy Course Technology/Cengage Learning

38 Intermediate Distribution Frame Telecom Closets

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+ Structured Cabling (cont’d.) Components Entrance facilities MDF (main distribution frame) Cross-connect facilities IDF (intermediate distribution frame) Backbone wiring Telecommunications closet Horizontal wiring Work area 41

+ Structured Cabling (cont’d.) Entrance facilities: The entrance facility is the point where the outdoor cable connects with the building’s backbone cabling. This is usually the demarcation point between the service provider and the customer owned systems. MDF (main distribution frame) Sometimes the MDF is simply known as the computer room or equipment room. First point in the network where LAN is connected with the service provider. MDF requires equipment capable of great throughput. 42

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+ Structured Cabling (cont’d.) Cross-connect facilities— The points where circuits interconnect with other circuits. Cross-connect devices allow large numbers of conducting wires to be mechanically interconnected in an organized fashion. There are two types of cross-connect devices: Punch-down blocks and Patch panels A punch-down block is a panel of data receptors into which twisted pair wire is inserted, or punched down, to complete a circuit. From a punch-down block, wires are distributed to a patch panel, a wall-mounted panel of data receptors. 44

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+ Structured Cabling (cont’d.) IDF (intermediate distribution frame)— A junction point between the MDF and concentrations of fewer connections Backbone wiring The cables or wireless links that provide interconnection between entrance facilities and MDFs, MDFs and IDFs, and IDFs and telecommunications closets. One component of the backbone is given a special term: vertical cross-connect. A vertical cross-connect runs between a building’s floors. For example, it might connect an MDF and IDF or IDFs and telecommunications closets within a building. The TIA/EIA standard designates distance limitations for backbones of varying cable types, as specified in Table 46

+ Structured Cabling (cont’d.) 47 Table 3-2 TIA/EIA specifications for backbone cabling Courtesy Course Technology/Cengage Learning

+ Structured Cabling (cont’d.) Telecommunications closet Also known as a “telco room,” it contains connectivity for groups of workstations in its area, plus cross-connections to IDFs or, in smaller organizations, an MDF. Large organizations may have several telco rooms per floor, but the TIA/EIA standard specifies at least one per floor. Telecommunications closets typically house patch panels, punch- down blocks, and connectivity devices for a work area. Because telecommunications closets are usually small, enclosed spaces, good cooling and ventilation systems are important to maintaining a constant temperature. 48

+ Structured Cabling (cont’d.) Horizontal wiring This is the wiring that connects workstations to the closest telecommunications closet. TIA/EIA recognizes three possible cabling types for horizontal wiring: STP, UTP, or fiber-optic cable. The maximum allowable distance for horizontal wiring is 100 m. This span includes 90 m to connect a data jack on the wall to the telecommunications closet plus a maximum of 10 m to connect a workstation to the data jack on the wall. 49

50 <= 10

+ Structured Cabling (cont’d.) Work area An area that encompasses all patch cables and horizontal wiring necessary to connect workstations, printers, and other network devices from their NICs to the telecommunications closet. The TIA/EIA standard calls for each wall jack to contain at least one voice and one data outlet. Realistically, you will encounter a variety of wall jacks. 51