CPMT 1449 Computer Networking Technology – Lesson 2 CPMT 1449 Computer Networking Technology – Lesson 2.1-Chapter 3 Transmission Basics and Networking Media

Learning Objectives Explain basic data transmission concepts, including full-duplexing, attenuation, latency, 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 best practices for cabling buildings and work areas

Transmission Basics Transmit – means to issue a signal Transmission – means the process of transmitting or the progress of a signal after it has been transmitted The picture below represents basic transmissions (very basic)

Analog Signaling Generated as voltage that varies continuously Characterized by 4 fundamental properties Amplitude - Frequency – The number of times the wave’s amplitude cycles from start to highest and lowest amplitude and back to the starting position over a fixed period of time Wavelength - Phase

Analog Signaling - Amplitude Amplitude - A measure of the signal’s strength at any given point in time

Analog Signaling – Frequency The number of times a wave cycles in a fixed period of time Start point Highest amplitude Lowest amplitude Expressed in Hertz (Hz) If the frequency is 1 cycle in 1 second 1 Hz, it is considered an extremely low frequency

Analog Signaling – Wavelength The distance between corresponding points on a wave’s cycle Expressed in meters or feet

Analog Signaling – Phase Is the progress of a wave over time in relationship to a fixed point Measured in degrees

Digital Signaling Composed of precise pulses of positive and zero voltages More reliable than analog signaling Less susceptible to noise Uses less overhead – Overhead is all the non-data information that must accompany the signal A positive voltage represents a 1 A zero voltage represent a 0 The 1’s and 0’s are indicative of the Binary system

Binary System Binary describes a numbering scheme in which there are only two possible values for each digit: 0 and 1 In the digital world, to count in binary, we have to understand the term bit and byte Bit – equals a single pulse and is represented by a 1 or a 0 Byte – equals 8 bits, this means that a byte contains 8 place holder as shown: 128 64 32 16 8 4 2 1, when these numbers are added together they equal 255 To count in binary, we place the eight bit values in their perspective place holder position We add the entire place holder values that have a bit value of 1 and ignore the bit holder values of 0….see the example.

Data Modulation Data relies on digital transmissions For networks that can only send data using analog signals the signal must be converted from digital to analog and back to digital this is called modulation and demodulation this is accomplished using a modulator/demodulator or what is commonly referred to as a modem Connecting to the internet is a good example of modulation/demodulation In modulation a simple wave called a carrier wave is combined with the data wave (see next slide) The carrier wave has preset properties (amplitude, frequency, wavelength, and phase) Frequency Modulation (FM) and Amplitude Modulation (AM) FM – the frequency of the carrier signal is modified by the application AM – the amplitude of the carrier signal is modified by the application

Data Modulation

Simplex/Half-Duplex/Full-Duplex Simplex is one-way communication Half-Duplex is two-way communication but not simultaneously Full-Duplex is two-way communication simultaneously Modern networks use full-duplex communications when sending and receiving data It is important to remember that if the network is using full-duplex all devices must use full-duplex

Multiplexing Allows multiple signals to be sent through a single transmission medium This requires the use of channels and sub-channels Channel – a distinct communication path Sub-channel the separation of a channel into multiple channels The channels are separated logically using a multiplexer/demultiplexer (mux/demux) The multiplexer takes all of the channels that are going to be multiplexed and combines them to be sent down a single medium. Once they arrive at the distant end, the channels are separated and sent to their separate destinations There are several types of multiplexing Time Division Multiplexing (TDM) Statistical Multiplexing Frequency Division Multiplexing (FDM) Wavelength Division Multiplexing (WDM) Dense Wavelength Division Multiplexing (DWMD)

Time Division Multiplexing and Statistical Multiplexing Divides the channels into multiple time slots A time slot is assigned to each node and in that time slot is that node’s data If a node has no data the time slot is wasted Statistical multiplexing eliminates the wasted time slots Senses an empty time slot and assigns the empty time slot to another node The arbitration for the unused time slot is factors such as use, priority, and other advanced factors

Time Division Multiplexing

Frequency Division Multiplexing Assigns a unique frequency band to each sub- channel The signals are modulated with different carrier frequencies Then multiplexed to travel over a single channel simultaneously Two common forms Cellular phone transmissions DSL internet access

Frequency Division Multiplexing

Wavelength Division Multiplexing Enables one fiber-optic connection to carry multiple light signals simultaneously One light beam is divided into 40 different carrier waves each with a different wavelength (color) Each wavelength is a different separate channel capable of transmitting up to 10Gbps Each carrier wave is modulated with a different data signal Lasers issue the modulated waves to the multiplexer that works like a prism, the waves are combined into a beam of white light It is then placed on a single strand of fiber by another laser and demuxed the same way at the distant end.

Dense Wavelength Division Multiplexing Most common for fiber networks Can carry between 80 and 160 channels Provides less separation between carrier waves Used on high-bandwidth or extremely long WAN links

Transmission Between Nodes Point-to-Point Involves one transmitter and one receiver Transmits data intended only for one receiver Typically these are WAN links Point-to-Multipoint One transmitter to 2 or more receivers Uses Broadcast or Non-broadcast transmissions Broadcast – sent to all nodes on that network Non-broadcast – sent to only specific nodes on that network

Throughput and Bandwidth Throughput - capacity See the throughput chart below Is the measure of data transmitted during a given time period Measured in bits per second (bps) Bandwidth – this term is normally used interchangeably with throughput Is actually the measure of the highest and lowest frequencies that a medium can transmit Measured in hertz (Hz)

Baseband and Broadband transmission form where digital signals are sent through the medium by direct current (DC) pulses Requires exclusive use of the wire’s capacity When a node transmits all other nodes must wait until that transmission ends Ethernet is an example of baseband communications Broadband Signal is modulated as radio Frequency (RF) analog waves Each wave uses different frequency ranges Does not encode information as digital signals Has two meanings in networking terms Meaning 1 – carries RF signal across multiple channels on coaxial cable Meaning 2 – several different network types that use digital signaling to transmit at extremely high transmission rates

Transmission Flaws Transmissions-analog or digital- are susceptible to degradation between the time they are sent until they are received Three major types Noise Attenuation Latency

Noise Any undesirable influence that is capable of distorting or degrading a signal Three major types Electromagnetic Interference (EMI) Radiofrequency Interface (RFI) Cross Talk – interference from a wire medium that is in close proximity of another wire medium The use of amplifiers and repeater help combat these three transmission flaws (Layer 1 devices)

Amplifiers and Repeaters Used to amplify analog signal Does not “clean” the noise out of the signal, but rather amplifies the signal and the noise Repeaters Used to regenerate digital signals Since the signal is regenerated the noise is not repeated

Attenuation and Latency The loss of the signal’s strength as it travels away from its source Attenuation is commonly seen at the wire medium that carries the signal to the transmission system’s antenna when using radios as the transmission systems Latency The delay of the signal or the time it takes to travel from sender to receiver. Commonly measured on networks via the round trip timer (RTT) and is measured in milliseconds (ms)

Connectors RJ45 Connectors BNC Connector Connectors connect the cable to the device Different cabling types use different connectors F-Type Connector RJ11 Connectors

Fiber Optic Connectors There are 10 different connectors used with fiber-optic cables. Listed are the most common ST Connector SC Connector LC Connector MT-RJ Connector

Unshielded Twisted Pair Networking Cables Shielded Twisted Pair (STP) Coaxial (coax) Fiber Optic (fiber) Unshielded Twisted Pair (UTP) There are several types of cabling that can be used concerning networks. Listed is the most common found in today’s modern networks

Terminating Twisted Pair Two standards

Twisted Pair Cable types 3 Types of Twisted Pair Cable Straight-through Crossover Rollover

Fiber Optic Cable Contains one or more fiber strands at its core Data is transmitted using pulsing light sent via lasers Each fiber is surrounded by cladding All is wrapped in Kevlar strands to protect the fiber core and then wrapped in a plastic sheath Has 2 types of fiber cable Single Mode Fiber (SMF) Multimode Fiber (MMF)

Single-Mode and Multi-Mode Fiber Single Mode Fiber Has a narrow core (>10 microns in diameter) Has very little reflection Has the highest bandwidth and can travel the longest distances Very expensive Multimode Fiber (create a graphic) Core has larger diameter (between 50-150 microns in diameter – normally 62.5 microns) Because of the core diameter, several pulses of light can be sent at different angles Extremely high through put Resistant to noise Good security Industry standard for high-speed networking

Fiber Optic Cable

Data Terminal Equipment (DTE)/Data Circuit Terminating Equipment (DCE) DTE refers to the user side of the cable – connects to equipment that is the responsibility of the user DCE side connects to a multiplexer or modem – required to provide timing to the DTE side of the cable TIA/EIA standard RS 232 (Recommended Standard 232) Uses DB-9 or DB-25 (most common)

End of Presentation For more information on this lesson, See Chapter 3 in the text book or email the Professor **All Slides and graphics were produced by Professor Patrick Hughes**