CIS 1140 Network Fundamentals Chapter 3 Transmission Basics and Networking Media

Collected and Compiled By JD Willard MCSE, MCSA, Network+, Microsoft IT Academy Administrator Computer Information Systems Instructor Albany Technical College

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– *Enter the password: student in the url window – Log in using the username: CIS 1140 or ATCStudent1 • If you should click on the demo link and you get an Access Denied it is because you have not logged in to vtc.com or you need to log out and log back in.

*Remember that passwords are case sensitive so enter it in all lower case letters.

Objectives

• Explain basic data transmission concepts, including full duplexing, attenuation, and noise • Describe the physical characteristics of coaxial cable, STP, UTP, and fiber-optic media • Compare the benefits and limitations of different networking media • Explain the principles behind and uses for serial connector cables • Identify wiring standards and the best practices for cabling buildings and work areas

Transmission Basics • In data networking, transmit means to issue signals to the network medium • Transmission refers to either the process of transmitting or the progress of signals after they have been transmitted

Network Cabling and Communication Overview Cabling Demo

Analog and Digital Signals

• Information transmitted via analog or digital signals – Signal strength proportional to voltage • In analog signals, voltage varies continuously and appears as a wavy line when graphed over time – Wave’s

amplitude

(the height of the wave) is a measure of its strength –

Frequency

: number of times wave’s amplitude cycles from starting point, through highest amplitude and lowest amplitude, back to starting point over a fixed period of time • Measured in Hz –

Wavelength

: distance between corresponding points on a wave’s cycle –

Phase

: progress of a wave over time in relationship to a fixed point • Analog transmission susceptible to transmission flaws such as noise

Analog and Digital Signals

• Digital signals composed of pulses of precise, positive voltages and zero voltages – Positive voltage represents 1 – Zero voltage represents 0 • Binary system: uses 1s and 0s to represent information – Easy to convert between binary and decimal • Bit: a single binary signal • Byte: 8 bits – Typically represents one piece of information • Overhead: describes non-data information that must accompany data for a signal to be properly routed and interpreted

Transmission Direction: Simplex, Half-Duplex, and Duplex

• Simplex transmission: signals may travel in only one direction (TV or Radio) • Half-duplex transmission: signals may travel in both directions over a medium – Only one direction at a time (Walkie Talkies or Intercom System) • Full-duplex or duplex: signals free to travel in both directions over a medium simultaneously (Telephone) – Used on data networks – Channel: distinct communication path between nodes • May be separated logically or physically

Full Duplex vs Half Duplex Demo

Transmission Direction: Multiplexing

• Multiplexing: transmission form allowing multiple signals to travel simultaneously over one medium – Channel logically separated into subchannels • Multiplexer (mux): combines multiple signals – Sending end of channel • Demultiplexer (demux): separates combined signals and regenerates them in original form – Receiving end of channel

Relationships Between Nodes

•Point-to-point transmission involves only one transmitter and one receiver.

•Point-to-multipoint transmission involves one transmitter and multiple receivers.

 Broadcasts involve one transmitter and multiple, undefined receivers  Nonbroadcast point-to-multipoint transmission issues signals to multiple, defined recipients

Throughput and Bandwidth

• Throughput: measure of amount of data transmitted during given time period • Measured in bits per second, kilobits per second, megabits per second etc.

• Probably most significant factor in choosing transmission method • Limited by signaling and multiplexing techniques used in given transmission method • Transmission methods using fiber-optic cables achieve faster throughput than those using copper or wireless connections • Noise and devices connected to transmission medium can limit throughput • Bandwidth: difference between highest and lowest frequencies that a medium can transmit • Measured in Hertz or cycles • 1 Hertz is the measure of a signal from its starting point to it’s highest amplitude to it’s lowest amplitude and back to the starting point

Baseband and Broadband

• Baseband: digital signals sent through direct current (DC) pulses applied to a wire – Requires exclusive use of wire’s capacity – Baseband systems can transmit one signal at a time – Half-duplex or duplex transmission – Ethernet • Broadband: signals modulated as radiofrequency (RF) analog waves that use different frequency ranges – Does not encode information as digital pulses – Simplex transmission

Communication Methods Demo

• • • • •

Transmission Flaws: Noise

Electromagnetic interference (EMI): waves emanating from electrical devices or cables Radio frequency interference (RFI): electromagnetic interference caused by radiowaves Crosstalk: signal traveling on a wire or cable infringes on signal traveling over adjacent wire or cable Certain amount of signal noise is unavoidable All forms of noise measured in decibels (dB)

Attenuation

Attenuation can be described as the loss of signal strength as the signal flows away from it’s source. It is caused by resistance on electrical networks and by optical loss on fiber optic networks.

An analog signal distorted by noise and then amplified A digital signal distorted by noise and then repeated

Latency

• Delay between transmission and receipt of a signal – Many possible causes: • Cable length • Intervening connectivity device (e.g., modems and routers) • Round trip time (RTT): Time for packets to go from sender to receiver and back • Cabling rated for maximum number of connected network segments • Transmission methods assigned maximum segment lengths

Network Cables

• A cable is the medium that provides the physical foundation for data transmission • Several types of cable are commonly used • Some networks use only one type of cable, while others employ several cable types • The type of cable chosen depends on: – The size of the network – The protocols being used – The network’s physical layout, or topology

Network Transmission Media Demo New and Old Cables and Connectors Demo

Common Media Characteristics: Throughput

• Probably most significant factor in choosing transmission method • Limited by signaling and multiplexing techniques used in given transmission method • Transmission methods using fiber-optic cables achieve faster throughput than those using copper or wireless connections • Noise and devices connected to transmission medium can limit throughput

Cost • Many variables can influence final cost of implementing specific type of media:

– Cost of installation – Cost of new infrastructure versus reusing existing infrastructure – Cost of maintenance and support – Cost of a lower transmission rate affecting productivity – Cost of obsolescence

Noise Immunity • Some types of media are more susceptible to noise than others

– Fiber-optic cable least susceptible

• Install cabling away from powerful electromagnetic forces

– May need to use metal conduit to contain and protect cabling

• Possible to use antinoise algorithms

Size and Scalability • Three specifications determine size and scalability of networking media:

– Maximum nodes per segment • Depends on attenuation and latency – Maximum segment length • Depends on attenuation, latency, and segment type • Populated segment contains end nodes – Maximum network length • Sum of network’s segment lengths

Connectors and Media Converters

• Connectors are the pieces of hardware that connect the wire to the network device.

• Every medium requires a specific kind of connector • Media converter: hardware enabling networks or segments running on different media to interconnect and exchange signals – Type of transceiver • Device that transmits and receives signals

Copper wire-to-fiber media converter

Coaxial Cable

• High resistance to noise; expensive • Impedance: resistance that contributes to controlling signal (expressed in ohms) • Thickwire Ethernet (Thicknet RG-8): original Ethernet medium – 10BASE-5 Ethernet • Thin Ethernet (Thinnet RG-58 /U): more flexible and easier to handle and install than Thicknet – 10BASE-2 Ethernet – Coax comes in many types, but their construction is similar: a central copper core surrounded by an insulator, a braided metal shielding, and an outer cover called the sheath or jacket

Coaxial Cable Demo

Coaxial Cable Types

The table below describes the different coaxial cable grades.

Grade Uses Conductor Resistance Rating

RG-58 Ethernet networking Tin-coated copper 50 ohms RG-59 Cable TV RG-6 RG-8 Satellite TV Thick Ethernet Copper-plated steel Solid copper Solid copper 75 ohms 75 ohms 50 ohms

Coaxial Connectors

• Connectors: pieces of hardware connecting wire to network device – Every networking medium requires specific kind of connector

Description Connector BNC

•Molded onto the cable •Used to create Ethernet network connections F-Type

F-type connector

•Twisted onto the cable •Used to create cable and satellite TV connections •Used to hook a cable modem to a broadband cable connection

Connectors Demo

• •

Twisted-Pair Cable

Twisted-Pair Cable: Color-coded pairs of insulated copper wires 0.4 to 0.8 mm in diameter, twisted in pairs around each other and encased in a plastic coating – The twists in a twisted-pair cable reduce the effect of crosstalk, the infringement of the signal from one wire pair on another wire pair’s signal; crosstalk is measured in decibels (dB), a measurement unit of signal strength of a sound’s intensity – The number of twists per inch determines how resistant the pair will be to noise but increases attenuation – TIA/EIA 568 standard divides twisted-pair wiring into several categories – Level 1 or CAT 3, 4, 5, 5e, 6, 6e, 7 – Is the most common form of cabling used on LANs – Is relatively inexpensive, easy to install, and capable of spanning significant distances before additional equipment is required – Can accommodate several different topologies, but is most often used in a star topology – Can handle the faster networking transmission rates in use today – Is available in unshielded, shielded and screened

Twisted Pair Cabling and Connectors Demo

Shielded Twisted-Pair (STP)

• Shielded Twisted-Pair (STP): – The cable consists of insulated wire pairs that are surrounded by a metal shielding, such as foil – The effectiveness of the shield depends on the environmental noise to which STP is subjected, the grounding mechanism, and the material, thickness, symmetry and consistency of the shielding – STP is more expensive than UTP, but does provide better immunity to EMI and RFI

• •

UTP (Unshielded Twisted-Pair)

Less expensive, less resistant to noise than STP – The cable contains color-coded pairs of insulated copper wires inside a plastic jacket – Each pair has a different number of twists per inch, depending on the grade, to help eliminate interference from adjacent pairs or cables Categories: – CAT 3 (Category 3): up to 10 Mbps of data at 16 MHz – CAT 4 (Category 4): 16 Mbps throughput at up to 20 MHz – CAT 5 (Category 5): up to 1000 Mbps throughput at 100 MHz – CAT 5e (Enhanced Category 5): higher twist ratio 350 MHz – CAT 6 (Category 6): six times the throughput of CAT 5. Wires encased in foil. 250 MHz – CAT 6e (Enhanced Category 6): reduced attenuation and crosstalk. Capable of 550 MHz.

– CAT 7 (Category 7): signal rates up to 1 GHz. Contains sheilding and uses different connectors.

Connector

Twisted Pair Connectors

Description

RJ-11 •Has 4 connectors •Supports up to 2 pairs of wires •Uses a locking tab to keep connector secure in outlet •Used primarily for telephone wiring RJ-45 •Has 8 connectors •Supports up to 4 pairs of wires •Uses a locking tab to keep connector secure in outlet •Used for Ethernet and some token ring connections

Comparing STP and UTP

• Throughput: STP and UTP can both transmit data at 10, 100, and 1000 Mbps – Depending on grade of cabling and transmission method used • Cost: STP usually more expensive than UTP • Connector: Both use RJ-45 and RJ-11 • Noise Immunity: STP more noise-resistant • Size and scalability: Max segment length for both is 100 m on 10BASE-T and 100BASE-T networks – Maximum of 1024 nodes

TIA/EIA 568A Series

• The T568A wiring standard is the most popular wiring standard currently in use for networks. In the T568A standard the green wire and the green and white striped wire transmits data from the device, while the orange and orange and white striped wire receives data from the network. • It typically doesn’t matter which scheme you choose, but to avoid confusion and potential transmission errors you should ensure that you cable all wiring on your LAN according to one standard.

TIA/EIA 568B Series

In the T568B standard the orange and orange and white striped wire transmits data from the device, while the green wire and the green and white striped wire receives data from the network.

Crossover Cable

•Crossover cables are used to wire two computer’s network cards together without the use of a hub/switch or to wire two hubs/switches together through their data ports (stacking) •To create a crossover cable wire one end of the cable 568A and the other end 568B

Straight-through Patch Cable Assembly Instructions

• Strip the cable jacket back about 3/4 of an inch from the end of the cable • Sort the pairs so they fit into the connector in the correct order • Insert the pairs into the connector • Crimp the pins with a crimp tool • Repeat for other end and test cable

Twisted Pair Wiring Tools

Fiber-Optic Cable

• • • • • • • Accommodates high bandwidths and long distances Benefits over copper cabling: – Nearly unlimited throughput – Very high resistance to noise – Excellent security – Ability to carry signals for much longer distances before requiring repeaters than copper cable – Industry standard for high-speed networking Throughput: transmission rates exceed 10 Gigabits per second Cost: most expensive transmission medium Connector: 10 different types of connectors – Typically use ST SC or MTRJ connectors Noise immunity: unaffected by EMI Size and scalability: segment lengths vary from 150 to 40,000 meters – Optical loss: degradation of light signal after it travels a certain distance away from its source

Fiber Optic Cable Demo

Type

Single Mode

Fiber Optic Cables

The table below describes the different fiber optic cable types.

Description

•Transfers data through the core using a single light ray (the ray is also called a •Expensive

mode

) •The core diameter is around 10 microns •Supports a large amount of data •Cable lengths can extend a great distance Multi mode •Transfers data through the core using multiple light rays •The core diameter is around 50 to 100 microns •Cable lengths are limited in distance

Figure 3-33 ST (straight tip) connector Figure 3-34 SC (subscriber connector or standard connector) Figure 3-35 LC (local connector) Figure 3-36 MT-RJ (mechanical transfer-register jack) connector

36

DTE (Data Terminal Equipment) and DCE (Data Circuit-Terminating Equipment) Connector Cables

• DTE (data terminal equipment) – Any end-user device • DCE (data circuit-terminating equipment) – Device that processes signals – Supplies synchronization clock signal • DTE and DCE connections – Serial • Pulses flow along single transmission line • Sequentially – Serial cable • Carries serial transmissions

DTE and DCE Connector Cables

• • •

Figure 3-37 DB-9 connector Figure 3-38 DB-25 connector

RS-232 (Recommended Standard 232) – EIA/TIA standard – Physical layer specification • Signal voltage, timing, compatible interface characteristics – Connector types • RJ-45 connectors, DB-9 connectors, DB-25 connectors RS-232 used between PC and router today RS-232 connections – Straight-through, crossover, rollover

Structured Cabling

• Structured cabling specifies standards without regard for the type of media or transmission technology used on the network. In other words, it is designed to work just as well for 10BaseT networks as it does for 100BaseFX networks.

• Structured cabling is based on a hierarchical design that divides cabling into subsystems. • You should be familiar with the principles of structured cabling before you attempt to design, install, or troubleshoot an organization’s cable plant.

• Cable plant: hardware making up enterprise wide cabling system

Structured Cabling

Figure 3-39 TIA/EIA structured cabling in an enterprise

• •

Cable Design and Management

Cable plant: hardware making up enterprise-wide cabling system Structured cabling: TIA/EIA’s 568 Commercial Building Wiring Standard – Entrance facilities point where building’s internal cabling plant begins • Demarcation point: division between service carrier’s network and internal network – Backbone wiring or Vertical cross connect: interconnection between telecommunications closets, equipment rooms, and entrance facilities – MDF (main distribution frame) also known as the main cross-connect or the Equipment room: Interconnection point between the LAN/WAN and the service provider’s facility. Location of significant networking hardware, such as servers and mainframe hosts

TIA/EIA structured cabling in a building

Cable Design and Management

– IDF (intermediate distribution frame) or telecommunications closet: contains connectivity for groups of workstations in area, plus cross connections to equipment rooms – Horizontal wiring: wiring connecting workstations to closest telecommunications closet – Work area: encompasses all patch cables and horizontal wiring necessary to connect workstations, printers, and other network devices from NICs to telecommunications closet

Horizontal Wiring Subsystem

•

Horizontal wirin

g — Wiring that connects workstations to the closest telecommunications closet. TIA/EIA recognizes three possible cabling types for horizontal wiring: STP, UTP, or fiber-optic. The maximum allowable distance for horizontal wiring subsystem 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 plus the cross connect.

Patch panel Patch panel Horizontal wiring

Wiring Rack

Punchdown block Patch Panel

“Telco Room”

Only twisted pair can be terminated in the punch down block.

Data Outlet

Data Outlet

Structured Cabling

TIA/EIA specifications for backbone cabling

Installing Cable

• Many network problems can be traced to poor cable installation techniques • Two methods of inserting UTP twisted pairs into RJ-45 plugs: TIA/EIA 568A and TIA/EIA 568B • Straight-through cable allows signals to pass “straight through” between terminations. Straight-through cables are used when connecting a PC to a Hub or Switch or when connecting Hubs together through their uplink ports.

• Crossover cable: termination locations of transmit and receive wires on one end of cable reversed. Crossover cables are used when connecting a PC directly to another PC without going through a Hub or when connecting or “stacking” two hubs together through their data ports.

Summary

• Information can be transmitted via two methods: analog or digital • In multiplexing, the single medium is logically separated into multiple channels, or subchannels • Throughput is the amount of data that the medium can transmit during a given period of time • Baseband is a form of transmission in which digital signals are sent through direct current pulses applied to the wire • Noise is interference that distorts an analog or digital signal • Analog and digital signals may suffer attenuation • Cable length contributes to latency, as does the presence of any intervening connectivity device • Coaxial cable consists of a central copper core surrounded by a plastic insulator, a braided metal shielding, and an outer plastic cover (sheath) • Twisted-pair cable consists of color-coded pairs of insulated copper wires • There are two types of twisted-pair cables: STP and UTP

Summary (continued)

• There are a number of Physical layer specifications for Ethernet networks • Fiber-optic cable provides the benefits of very high throughput, very high resistance to noise, and excellent security • Fiber cable variations fall into two categories: single-mode and multimode • Structured cabling is based on a hierarchical design that divides cabling into six subsystems • The best practice for installing cable is to follow the TIA/EIA 568 specifications and the manufacturer’s recommendations • Wireless transmission requires an antenna connected to a transceiver • Infrared transmission can be used for short-distance transmissions

The End