Introduction to Computer Networks PDF

Introduction to Computer Networks Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Objecti...

Introduction to Computer Networks Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Objectives Describe basic computer components and operation Explain the fundamentals of network communication Define common networking terms Compare different network models Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  An Overview of Computer Concepts Most devices encountered when working with a network involve a computer Most obvious devices are workstations and network servers running operating systems such as: Windows, Linux, UNIX, and Mac OS Also includes routers and switches Specialized computers used to move data from computer to computer and network to network You will learn more about them in later chapters Nontraditional computers include: Smartphones, smart watches, home assistants like Amazon Echo and Google Home, and smart “things” such as appliances, and thermostats Smart things are collectively referred to as Internet of Things (IOT) devices Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Basic Functions of a Computer (1 of 4) A computer’s functions can be broken down into three basic tasks: Input: A user types the letter ‘A’ on the keyboard, which results in sending a code representing the letter ‘A’ to the computer Processing: The computer’s CPU determines what letter was typed by looking up the keyboard code in a table Output: The CPU sends instructions to the graphics cards to display the letter ‘A’, which is then sent to the computer monitor Some computer components are designed to perform only one of these three functions Others are designed to perform two or all three functions Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Basic Functions of a Computer (2 of 4) Input Components Includes user controlled devices such as keyboards, microphones, Webcams, and scanners External interfaces, such as serial, FireWire, and USB ports can also be used to get input from external devices. Input is also generated by storage devices such as hard disks and CDs/DVDs Inputs to a computer can include timers that cause programs to run periodically Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Basic Functions of a Computer (3 of 4) Processing Components The CPU is a computer’s main processing component CPUs execute instructions from computer programs, such as word processors and from the computer’s operating system Current CPUs are composed of two or more processors called cores A multicore CPU is like a person with two brains Multicore CPUs enable computers to carry out multiple instructions simultaneously ▶ Results in better overall performance Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Basic Functions of a Computer (4 of 4) Output Components The most obvious are monitors and printers Also include storage devices, network cards, and sound cards External interfaces For example, a disk drive connected to a USB port allows reading files from the disk (input) and writing files to the disk (output) Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Storage Components (1 of 5) The more storage a computer has, the better the performance Most storage components are both input and output devices Most people think of storage as disk drives, CD/DVD drives, and USB flash drives. There are two main categories of storage: Short-term storage Long-term storage Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Storage Components (2 of 5) RAM: Short-Term Storage Random Access Memory (RAM) is short-term storage because when power to the computer is turned off, RAM’s contents are gone The amount of RAM in a computer is crucial to the computer’s capability to operate efficiently RAM is also referred to as “working storage” If there’s not enough RAM to run a program, the computer will use the disk drive to supplement Temporary use of the disk drive is not optimal because RAM is thousands of times faster than the fastest disk drives Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Storage Components (3 of 5) Long-Term Storage Long-term storage maintains its data even when there’s no power Examples: Hard disks CDs/DVDs Solid state drives (SSDs) USB flash drives Long-term storage is used to store document and multimedia files As well as application and OS files The amount of storage a computer needs depends on the type and quantity of files to be stored Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Storage Components (4 of 5) Data Is Stored In Bits Data on a computer is stored as binary digits (“bits” for short) A bit holds a 1 or 0 value A pulse of 5 volts of electricity can represent a 1 bit and a pulse of 0 volts (the absence of voltage) can represent a 0 bit With fiber-optic cable, a 1 bit is represented by the presence of light and a 0 bit by the absence of light A “byte” is a collection of 8 bits Table 1-2 on the following slide shows prefixes used for expressing bits and bytes Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Personal Computer Hardware (1 of 7) Four major PC components: Motherboard Storage device RAM Firmware The Motherboard and Its Components The motherboard is a network of wires and controlling circuits that connects all computer components Key components of a motherboard are labeled in Figure 1-1 and explained in Table 1-3 on the slide following Figure 1-1 Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Personal Computer Hardware (2 of 7) Figure 1-1 A PC motherboard Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Personal Computer Hardware (3 of 7) Component Description CPU socket The CPU is installed in this socket PCI Express bus Used to add functionality to a PC by adding expansion cards that have a PCIe expansion slots connector. The larger slots are suitable for high-performance expansion cards, such as graphics cards and disk controllers. Smaller slots are best suited to sound cards and network interface cards. PCI bus expansion slots This older expansion card standard is rarely found on new computers. RAM slots Slots for installing RAM on the motherboard. Chipset with heat sinks The chipset consists of two chips referred to as the Northbridge and the Southbridge. These chips control data transfers between memory, expansion slots, I/O devices, and the CPU. The heat sink sits on top of the chipset to prevent overheating. SATA connectors Used for connecting hard drives and CD/DVD drives that use the SATA specification. IDE connector Used for connecting IDE hard drives and CD/DVD-ROM drives. Main power connector This connector is where the motherboard receives power from the system power supply. Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Personal Computer Hardware (4 of 7) Computer Bus Fundamentals A bus is a collection of wires carrying data from one place to another on the computer All data that goes into or comes out of a computer goes through the motherboard There are buses between: CPU and RAM CPU and disk drives CPU and expansion slots Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Personal Computer Hardware (5 of 7) Storage Device Fundamentals Hard drive is the primary long-term storage component on a computer Consists of magnetic disks called “platters” that store data in the form of magnetic pulses Hard disks store the documents you use as well as the applications that open those documents Also stores the OS your computer loads when it boots Solid State Drives SSDs are used in place of hard drives due to speed and reliability SSDs use flash memory Contains no moving parts and has faster access times SSDs are more expensive than hard drives and are often found in mobile devices Also found in high-performance desktops and servers Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Personal Computer Hardware (6 of 7) RAM Fundamentals RAM is the main short-term storage component on a computer Because RAM requires continuous power to store data it is referred to as “volatile memory” RAM has no moving parts so accessing data in RAM is much faster than accessing data on a hard drive In general, the more RAM your system has the faster it will run Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Personal Computer Hardware (7 of 7) Firmware Fundamentals Firmware is a computer program stored in nonvolatile memory such as ROM or flash memory It is located on the motherboard and is executed when the computer is powered on Firmware on most PCs is called the basic input/output system (BIOS) or Unified Extensible Firmware Interface (UEFI) Tells the CPU to perform certain tasks when power is first applied to the computer One of those instructions is to perform a power-on self test (POST) When a computer boots, the firmware program offers a chance to run the Setup utility in order to configure hardware components This configuration is stored in a type of memory called complementary metal oxide semiconductor (CMOS) Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Computer Boot Procedure To take a computer from a powered-off state to running an OS, the following steps must take place: 1. Power is applied to the motherboard 2. The CPU starts 3. The CPU carries out the BIOS startup routines, including the POST 4. Boot devices, as specified in the BIOS configuration, are searched for an OS 5. The OS is loaded into RAM 6. OS services are started Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  The Fundamentals of Network Communication A computer network consists of two or more computers connected by some kind of transmission medium Such as a cable or air waves In order to access the Internet, a computer has to be able to connect to a network The next few slides will cover what is required to turn a standalone computer into a networked computer Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Network Components (1 of 4) Hardware components needed to turn a stand-alone computer into a networked computer: Network interface card is an add-on card plugged into a motherboard expansion slot that provides a connection between the computer and the network Network medium is a cable that plugs into the NIC and makes the connection between a computer and the rest of the network Network media can also be the air waves, as in wireless networks Interconnecting device allows two or more computers to communicate on the network without having to be connected directly to one another Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Network Components (2 of 4) Figure 1-5 A network of computers connected to a switch Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Network Components (3 of 4) Network software can be divided into the following categories: Network clients and servers Network client software requests information stored on another network computer or device Network server software allows a computer to share its resources Protocols Network protocols define the rules and formats a computer must use when sending information across the network NIC driver NIC drivers receives data from protocols and forwards this data to the physical NIC Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Network Components (4 of 4) Figure 1-6 The properties of a network connection in Windows Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Steps of Network Communication 1. Application tries to access a network resource by sending a message 2. Client software formats the message and passes the message on to the network protocol 3. Protocol packages the message in a format suitable for the network and sends it to the NIC driver 4. NIC driver sends data in the request to the NIC card to be converted into necessary signals to be transmitted on the network Steps taken at the server side are essentially the reverse of those on the client side Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Layers of the Network Communication Process (1 of 3) Each step required for a client to access network resources is referred to as a “layer” Each layer has a task and all layers work together Figure 1-7 depicts this process Table 1-4 maps the resource access steps Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Layers of the Network Communication Process (2 of 3) Figure 1-7 Layers of the network communication process Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Layers of the Network Communication Process (3 of 3) Step Description Layer 1 An application tries to access a network resource. User application 2 Client software detects the attempt to access the network and Network client or server software passes the message on to the network protocol. 3 The protocol packages the message in a format suitable for the Network protocol network and sends it to the NIC driver. 4 The NIC driver sends the data in the request to the NIC, which Network interface converts the data into the necessary signals to be transmitted across the network medium. Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  How Two Computers Communicate on a LAN: Some Details (1 of 3) TCP/IP is the most common protocol (language) used on networks TCP/IP uses 2 addresses to identify devices Logical address (IP address) Physical address (MAC address) Just as a mail person needs an address to deliver mail, TCP/IP needs an address in order to deliver data to the correct device on a network Think of the Logical address as a zip code and the Physical address as a street address Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  How Two Computers Communicate on a LAN: Some Details (2 of 3) 1. A user at Comp A types ping 10.1.1.2 at a command prompt 2. Network software creates a ping message 3. The network protocol packages the message by adding IP address of sending and destination computers and acquires the destination computer’s MAC address 4. The network interface software adds MAC addresses of sending and destination computers 5. Comp B receives message, verifies that the addresses are correct and then sends a reply to Comp A using Steps 2 – 4 Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. How Two Computers Communicate on a LAN: Some Details (3 of 3) Figure 1-8 Communication between two computers Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Network Terms Explained Every profession has its own language and acronyms It is essential to know the language of networks to be able to study them Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  LANs, Internetworks, WANs, and MANs (1 of 7) Local area network (LAN) is a small network, limited to a single collection of machines and connected by one or more interconnecting devices in a small geographic area An internetwork is a networked collection of LANs tied together by devices such as routers Reasons for creation: Two or more groups of users and their computers need to be logically separated but still need to communicate Number of computers in a single LAN has grown and is no longer efficient The distance between two groups of computers exceeds the capabilities of most LAN devices Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. LANs, Internetworks, WANs, and MANs (2 of 7) Figure 1-14 A LAN with computers interconnected by a switch Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. LANs, Internetworks, WANs, and MANs (3 of 7) Figure 1-15 A wireless LAN Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. LANs, Internetworks, WANs, and MANs (4 of 7) Figure 1-16 A LAN with a symbolic hub (left) and a symbolic switch (right) Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. LANs, Internetworks, WANs, and MANs (5 of 7) Figure 1-18 An internetwork with two LANs connected by a router Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  LANs, Internetworks, WANs, and MANs (6 of 7) Wide area networks (WANs) use the services of third-party communication providers to carry network traffic from one location to another Metropolitan area networks (MANs) use WAN technologies to interconnect LANs in a specific geographic region, such as a county of city Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. LANs, Internetworks, WANs, and MANs (7 of 7) Figure 1-19 A WAN with a connection to the Internet Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Internet, Intranet, and Extranet The Internet is a worldwide public internetwork Uses protocols such as TCP/IP and HTTP to transfer and view information An intranet is a private internetwork in which devices and servers are only available to those users connected to the internal network An extranet allows limited and controlled access to internal resources by outside users Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Packets and Frames (1 of 2) Computers transfer information across networks in shorts bursts of about 1500 bytes of data Reasons data is transferred this way: Pause between bursts allows other computers to transfer data during pauses Allows the receiving computer to process received data Allows the receiving computer receive data from other computers at the same time Gives the sending computer an opportunity to receive data from other computers and perform other processing tasks If an error occurs during transmission of a large file, only the chunks of data involved in the error have to be sent again Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Packets and Frames (2 of 2) Packets Chunks of data sent across the network are usually called “packets” or “frames”, with packets being the more well-known term Packet is a chunk of data with a source and destination IP address added to it Using the U.S. mail analogy, you can look at a packet as an envelope that has had the zip code added to the address but not the street address Frames Frame is a packet with the source and destination MAC addresses added to it The packet is “framed” by the MAC addresses on one end and an error-checking code on the other The process of adding IP addresses and MAC addresses to chunks of data is called encapsulation Information added to the front of the data is called a header and information added to the end is called a trailer Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Clients and Servers (1 of 2) A client can be a workstation running a client OS or it can refer to the network software on a computer that requests network resources from a server Client The word “client” is usually used in these three contexts: Client operating - system is the OS installed on a computer Client computer - primary role is to run user applications and access network resources Client software - software that requests network resources from server software on another computer Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Clients and Servers (2 of 2) Server A computer becomes a server when software is installed on it that provides a network service to client computers The term “server” is also used in three contexts: Server operating system – OS installed on a computer designed to share network resources and provide other network services Server computer – a computer’s primary role in the network is to give client computers access to network resources and services Server software – responds to requests for network resources from client software Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Network Models A network model defines how and where resources are shared and how access to these resources is regulated Network models fall into two major types: Peer-to-peer network – most computers function as clients or servers (no centralized control over who has access to network resources) Server-based network – certain computers take on specialized roles and function mainly as servers, and ordinary users’ machines tend to function mainly as clients Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Peer-to-Peer/Workgroup Model Computers on a peer-to-peer network can take both a client and a server role Any user can share resources on his/her computer with any other user’s computer Every user must act as the administrator of his/her computer Can give everyone else unlimited access to their resources or grant restricted access to other users Usernames and passwords (credentials) are used to control that access Problems with peer-to-peer networks: Must remember multiple sets of credentials to access resources on several computers Desktop PCs and the OS installed on them aren’t made to provide network services as efficiently as dedicated network servers Data organization If every machine can be a server, how can users keep track of what information is stored on which machine? Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Server/Domain-Based Model (1 of 4) Server-based networks allow centralized control over network resources Users log on to the network with a single set of credentials maintained by one or more servers running a server OS In most cases, servers are dedicated to running network services and should not be used to run user applications A domain is a collection of users and computers whose accounts are managed by Windows servers called domain controllers Users and computers in a domain are subject to network access and security policies defined by a network administrator The software that manages this security is referred to as a directory service. On Windows servers, the directory service software is Active Directory Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Server/Domain-Based Model (2 of 4) Other network services found on network servers: Naming services – translate computer names to their address E-mail services – manage incoming and outgoing email Application services – grant client computers access to complex applications that run on the server Communication services – give remote users access to a network Web services – provide comprehensive Web-based application services Server-based networks are easier to expand than peer-to-peer Peer-to-peer should be limited to 10 or fewer users Server-based networks can handle up to thousands of users Multiple servers can be configured to work together which can be used to run a more efficient network or can provide fault tolerance Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Server/Domain-Based Model (3 of 4) Table 1-6 on the following slide summarizes the strengths and weaknesses of peer-to-peer and server-based networks Greg Tomsho, Guide to Networking Essentials, 8th Edition. © 2020 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.