Prepared by Agha Mohammad Haidari Network Manager ICT Directorate Ministry of Communication & IT

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1 Network Basics Prepared by Agha Mohammad Haidari Network Manager ICT Directorate Ministry of Communication & IT Cell:

2 After this lesson,you will be able to : Define a computer network Discuss advantages of using a networking Describe a local area network (LAN) and a Wide area network (WAN) Identify the primary difference between a LAN,MAN and WAN

3 Basics of Networking What is a Network? A Network is a connection of two or more Computers to share Resources and computer network consists of two computers connected to each other by a cable that allows them to share data.

4 Basics of Networking What is a Network? A network is a collection of computers, printers, routers, switches, and other devices that are able to communicate with each other over some transmission.

6 Why Use a Computer Network? Sharing information (or data) Sharing hardware and software Centralizing administration and support message Word-processing Software Illustration,photographs,videos, and audio files Live audio and video broadcasts

7 Why Use a Computer Network? Printers Fax machines Modems CD-ROM drives Hard drives

8 Categories of Networks Network Local area network (LAN) Metropolitan area Network (MAN) Wide area network (WAN)

9 Local Area Network (LAN) A Local Area Network (LAN) is a group of computers and network communication devices within a limited geographic area, such as an office building. They are characterized by the following: High data transfer speeds Generally less expensive technologies Limited geographic area

11 LANs consist of the following components Computers Network interface cards Networking media Network devices

12 LANS are Designed to : Operate Within a limited geographic area Allow multi-access to high-bandwidth media Control the network under local administration Connect physically devices LANs make it possible for businesses that use computer technology to locally share files and printers efficiently, and make internal communications possible

13 Wide Area Network (WAN) A Wide Area Network (WAN) interconnects LANs. It is not restricted to a particular geographic area and may be interconnected around the world. They are characterized by the following: Multiple interconnected LANs. Wide Area Network connect larger geographic area. Such is countries in the world.

15 WANs are designed to do the following Operate over a large geographically separated areas Allow users to have real-time communication capabilities with other users Provide full-time remote resources connected to local services Provide , World Wide Web, file transfer, and e-commerce services

16 Metropolitan Area Network A MAN is a network that spans a metropolitan area such as a city or suburban area. A MAN usually consists of two or more LANs in a common geographic area. For example, a bank with multiple branches may utilize a MAN. Typically, a service provider is used to connect two or more LAN sites using private communication lines or optical services. A MAN can also be created using wireless bridge technology by beaming signals across public areas

18 What is Bandwidth? Bandwidth is defined as the amount of information that can flow through a network connection in a given period of time. It is essential to understand the concept of bandwidth when studying networking for the following two reasons

19 Why bandwidth is important? Bandwidth is limited by physics and technology. Bandwidth is not Free

20 Bandwidth is finite In other words, regardless of the media used to build the network, there are limits on the capacity of that network to carry information. Bandwidth is limited by the laws of physics and by the technologies used to place information on the media. For example, the bandwidth of a conventional modem is limited to about 56 kbps by both the physical properties of twisted-pair phone wires and by modem technology. However, the technologies employed by DSL also use the same twisted-pair phone wires, yet DSL provides much greater bandwidth than is available with conventional modems. So, even the limits imposed by the laws of physics are sometimes difficult to define. Optical fiber has the physical potential to provide virtually limitless bandwidth. Even so, the bandwidth of optical fiber cannot be fully realized until technologies are developed to take full advantage of its potential o

21 Bandwidth is not free It is possible to buy equipment for a local-area network (LAN) that will provide nearly unlimited bandwidth over a long period of time. For wide-area network (WAN) connections, it is almost always necessary to buy bandwidth from a service provider. In either case, an understanding of bandwidth and changes in demand for bandwidth over a given time can save an individual or a business a significant amount of money. A network manager needs to make the right decisions about the kinds of equipment and services to buy

22 Unit of Bandwidth Bit per Second (bps) Kilobits per second 1kbps=1,000 bps Megabits per second 1Mbps=1,000,000 bps Gigabits per second 1Gbps=1,000,000,000 Terabits per second 1Tbps=1,000,000,000,000 o

23 What is Throughput? Throughput refers to actual measured bandwidth, at a specific time of day, using specific Internet routes, and while a specific set of data is transmitted on the network. Unfortunately, for many reasons, throughput is often far less than the maximum possible digital bandwidth of the medium that is being used

24 The following are some of the factors that determine throughput Internetworking devices Type of data being transferred Network topology Number of users on the network User computer Server computer

25 Categories of Networks in LAN Peer-to-peer network Client Server network Server Computers that Provide shared resources to network user Clients Computers that access shared network resources Provide by a server Media The wires that make the physical connections. Shared data Files provided to clients by servers across the network. Resources Any Service or device,such as files,printers,or other items,made available for use by members of the network.

27 Peer-to-Peer Networks By using LAN and WAN technologies, many computers are interconnected to provide services to their users. To accomplish this, networked computers take on different roles or functions in relation to each other. Some types of applications require computers to function as equal partners. Other types of applications distribute their work so that one computer functions to serve a number of others in an unequal relationship. In either case, two computers typically communicate with each other by using request/response protocols. One computer issues a request for a service, and a second computer receives and responds to that request. The requestor takes on the role of a client, and the responder takes on the role of a server

28 Peer-to-Peer Networks In a peer-to-peer network, networked computers act as equal partners, or peers. As peers, each computer can take on the client function or the server At one time, computer A may make a request for a file from.function computer B, which responds by serving the file to computer A. Computer A functions as client, while B functions as the server. At a later time, computers A and B can reverse roles In a peer-to-peer network, individual users control their own resources. The users may decide to share certain files with other users. The users may also require passwords before allowing others to access their resources. Since individual users make these decisions, there is no central point of control or administration in the network. In addition, individual users must back up their own systems to be able to recover from data loss in case of failures. When a computer acts as a server, the user of that machine may experience reduced performance as the machine serves the requests made by other systems o

29 Peer-to- Peer Networks

30 Clients Server Networks In a Clients Server Networks one or more computers act as servers and provide the resources to the network.the other computers are clients and use the resources provided by the server. In a client/server arrangement, network services are located on a dedicated computer called a server. The server responds to the requests of clients. The server is a central computer that is continuously available to respond to requests from clients for file, print, application, and other services. Most network operating systems adopt the form of a client/server relationship. Typically, desktop computers function as clients and one or more computers with additional processing power, memory, and specialized software function as servers

31 Clients Server Networks

32 Comparison of Peer-to-Peer Networks and Clients Server Networks Peer-to-Peer Networks Clients Server Networks Good for 10 or fewer computers. limited only by server and network hardware Security established by the user of Extensive and consistent resource and user Each computer. Security. Individual users responsible for their Centrally located for network control, requires Own administration, no full-time at least one knowledgeable administrator Administration necessary.

36 Connecting Devices Connecting Devices Networking Devices Internetworking Devices Repeaters Switches Bridges Hubs Routers Gateways

37 What is Repeater? The purpose of a repeater is regenerate and retime network signals at the bit level to allow them to travel a longer distance on the media. A repeater receives a signal, regenerates it, and passes it on. It can regenerate and retime network signals at the bit level to allow them to travel a longer distance on the media. The Four Repeater Rule for 10-Mbps Ethernet should be used as a standard when extending LAN segments. This rule states that no more than four repeaters can be used between hosts on a LAN. This rule is used to limit latency added to frame travel by each repeater. Too much latency on the LAN increases the number of late collisions and makes the LAN less efficient

39 What is Hub? Hubs are actually multiport repeaters. In many cases, the difference between the two devices is the number of ports that each provides. While a typical repeater has just two ports, a hub generally has from four to twenty-four ports. Hubs are most commonly used in Ethernet 10BASE-T or 100BASE-T networks, although there are other network architectures that use them as well. Using a hub changes the network topology from a linear bus, where each device plugs directly into the wire, to a star. With hubs, data arriving over the cables to a hub port is electrically repeated on all the other ports connected to the same network segment, except for the port on which the data was sent.

41 Hubs come in three basic types: Passive: A passive hub serves as a physical connection point only. It does not manipulate or view the traffic that crosses it. It does not boost or clean the signal. A passive hub is used only to share the physical media. As such, the passive hub does not need electrical power Active: An active hub must be plugged into an electrical outlet because it needs power to amplify the incoming signal before passing it out to the other ports Intelligent: Intelligent hubs are sometimes called smart hubs. These devices basically function as active hubs, but also include a microprocessor chip and diagnostic capabilities. Intelligent hubs are more expensive than active hubs, but are useful in troubleshooting situations

Hub: Devices attached to a hub receive all traffic traveling through the hub. The more devices there are attached to the hub, the more likely there will be collisions.

42 Hub: Devices attached to a hub receive all traffic traveling through the hub. The more devices there are attached to the hub, the more likely there will be collisions. A collision occurs when two or more workstations send data over the network wire at the same time. All data is corrupted when that occurs. Every device connected to the same network segment is said to be a member of a collision domain Sometimes hubs are called concentrators, because hubs serve as a central connection point for an Ethernet LAN

43 What is Bridge There are times when it is necessary to break up a large LAN into smaller, more easily managed segments. This decreases the amount of traffic on a single LAN and can extend the geographical area past what a single LAN can support. The devices that are used to connect network segments together include bridges, switches, routers, and gateways. Switches and bridges operate at the Data Link layer of the OSI model. The function of the bridge is to make intelligent decisions about whether or not to pass signals on to the next segment of a network. When a bridge receives a frame on the network, the destination MAC address is looked up in the bridge table to determine whether to filter, flood, or copy the frame onto another segment

44 Bridge 127 Hub Hub Segment 1 Corporate Intranet Segment 2

45 What is Switch? A switch is sometimes described as a multiport bridge. While a typical bridge may have just two ports linking two network segments, the switch can have multiple ports depending on how many network segments are to be linked. Like bridges, switches learn certain information about the data packets that are received from various computers on the network. Switches use this information to build forwarding tables to determine the destination of data being sent by one computer to another computer on the network

46 Cisco Switch

48 What is Router? Router is the first device that you will work with that is at the OSI network layer, or otherwise known as layer 3 Routers make decisions based on groups of network addresses (classes) as opposed to individual layer 2 MAC addresses Because of their ability to route packets based on layer 3 information, routers have become the backbone of the internet, running the IP protocol. Routers have all the capabilities listed above. Routers can regenerate signals, concentrate multiple connections, convert data transmission formats, and manage data transfers. They can also connect to a WAN, which allows them to connect LANs that are separated by great distances. None of the other devices can provide this type of connection

50 What is Gateways? A network gateway is an internetworking system A system that joins two networks together,a network gateway can be implemented completely in software Completely in hardware,or as a combination of the Two.depending on their implementation,network gateways can operate at any level of the OSI model form application protocols to low level signaling.

51 What is a Network Interface Cards? The network interface Card (NIC) provide the physical connection between the network and the computer workstation The function of a NIC is to connect a host device to the network medium. A NIC is a printed circuit board that fits into the expansion slot on the motherboard or peripheral device of a computer. The NIC is also referred to as a network adapter. On laptop or notebook computers a NIC is the size of a credit card. NICs are considered Layer 2 devices because each NIC carries a unique code called a MAC address. This address is used to control data communication for the host on the network. More will be learned about the MAC address later. As the name implies, the network interface card controls host access to the medium.

53 What is a workstations? The user computers connected to a network are called workstations.

54 What is a Protocols? Protocols are rules and procedures for communication. Protocols are the language of computers. If computers want to talk to one another, they must speak the same language, or in other words, use the same protocol. If they don t use the same protocol, they cannot exchange information. The good.

55 What is a Protocols? thing about Windows 2003 is that it supports many of the common network protocols in use today, which makes it a good choice of operating system to use in different types of networks.

56 What is a Protocols? Protocols are sets of rules that define how computers and components interact with one another. They are developed either by a single entity or by an organization made up of a group of entities. The International Organization for Standardization (ISO), located in Geneva, Switzerland, is responsible for developing and publishing standards. This group designed a standard that is used as a model for network communication, the Open Systems Interconnection (OSI) reference model.

57 What is Internet Protocols? A machine may be connected by millions of other machines across the internet, and there is no single cable connecting all those computers; but there is a logical connection in the sense that you can use a program like telnet to connect from a computer in California to another in Germany. But how do the packets being sent get from one place by another? How can the local network in California be prevented from being overloaded with packets sent from multiple machines in Germany and, at the same time, ensure that these telnet packets get through?.(the answer is provided by the Internet Protocol (IP

58 Network Topology Network topology defines the structure of the network. The physical topology, which is the actual layout of the wire or media, and the logical topology, which defines how the media is accessed by the hosts for sending data.

59 What is Bus Topology? Bus - single backbone segment (length of cable) that all the hosts connect to directly

60 Advantages of Bus Topology: Use of cable is economical Media is inexpensive and easy to work with System is simple and reliable. Bus is easy to extend Disadvantages of Bus Topology: Problems are difficult to isolate Cable break can affect many users Network can slow down in heavy traffic

62 What is Ring Topology? Ring - connects one host to the next and the last host to the first.

63 Advantages of Ring Topology: Performance is System provides equal access for all computers even despite many users Disadvantages of Ring Topology: Failure of one computer can impact the rest of the network Problems are hard to isolate.

65 What is Star Topology? Star - connects all cables to a central point of concentration.

66 Advantages of Star Topology Centralized.Modifying system and adding new computers is easy monitoring and management are possible Failure of one computer does not affect the rest of the network Disadvantages of Star Topology : If the centralized point fails, the network fails

68 What is Extended Star Topology? Extended star - uses the star topology to be created, links individual stars together by linking the hubs/switches, extend the length and size of the network.

70 What is Hierarchical Topology? Hierarchical - system is linked to a computer that controls the traffic on the topology.

72 What is Mesh Topology? Mesh - used when there can be absolutely no break in communications, each host has its own connections to all other hosts.

73 Advantages of Mesh Topology : System provides increased redundancy and reliability as well as ease of troubleshooting. Disadvantages of Mesh Topology: System provides increased redundancy and reliability as well as ease of troubleshooting.

75 Thanks any?

Chapter One: Networking Fundamentals Computer Networks

Chapter One: Networking Fundamentals Computer Networks 1.1 Bandwidth Bandwidth is defined as the amount of information that can flow through a network connection in a given period of time. It is important to understand the concept of bandwidth for the following