Computer Networking Fundamental EC301 Introduction to Networking Introduction to Networking Basic concepts and components of computer networks Networking Standards Principles of communication in networking Functions of Networking Hardware 1
What is a network? Why we use network? Network definition A combination of computer hardware, cabling, network devices, and computer software used together to allow computers to communicate with each other. Group of computers and other devices that are connected by some type of transmission media. 2
Why Use Networks? Using networks offers advantages relative to using a stand-alone computer Computer network Stand-alone computer The advantages of networked computing relative to standalone computing. Fewer Peripherals Needed Many devices can be connected on a network. Increased Communication Capabilities Networks provide several different collaboration tools that can be used to communicate between network users. Avoid File Duplication and Corruption A server manages network resources. Servers store data and share it with users on a network. 3
The advantages of networked computing relative to standalone computing. Lower Cost Licensing Application licensing can be expensive for individual computers. Centralized Administration Centralized administration reduces the number of people needed to manage the devices and data on the network, reducing time and cost to the company. Conserve Resources Data processing can be distributed across many computers to prevent one computer from becoming overloaded with processing tasks. Fundamental types of networks Peer-to-peer networks Client/server networks 4
Peer-to-peer networks Every computer can communicate directly with every other computer By default, no computer has more authority than another Every computer is capable of sending and receiving information to and from every other computer Peer-to-peer networks Advantages of a peer-to-peer network: Less initial expense - No need for a dedicated server. Setup - An operating system (such as Windows XP) already in place may only need to be reconfigured for peer-to-peer operations. Disadvantages of a peer-to-peer network: Decentralized - No central repository for files and applications. Security - Does not provide the security available on a client/server network. 5
Client/server networks Server central computer used to facilitate communication and resource sharing between other computers on the network (called clients) Client/server network uses a server to enable clients to share data, data storage space, and devices To function as a server, a computer must be running a network operating system (NOS) Most of the concepts on the Network+ exam pertain to client/server networks Client/server networks Advantages of a client/server network: Centralized - Resources and data security are controlled through the server. Scalability - Any or all elements can be replaced individually as needs increase. Flexibility - New technology can be easily integrated into system. Interoperability - All components (client/network/server) work together. Accessibility - Server can be accessed remotely and across multiple platforms. 6
Client/server networks Disadvantages of a client/server network: Expense - Requires initial investment in dedicated server. Maintenance - Large networks will require a staff to ensure efficient operation. Dependence - When server goes down, operations will cease across the network. The advantages Client/server networks over peer-to-peer networks User logon accounts and passwords can be assigned in one place Access to multiple shared resources can be centrally granted to a single user or groups of users Problems can be tracked, diagnosed, and often fixed from one location 7
The advantages Client/server networks over peer-to-peer networks Servers are optimized to handle heavy processing loads and dedicated to handling requests from clients, enabling faster response time Because of their efficient processing and larger disk storage, servers can connect more than a handful of computers on a network The classifications of networks LAN MAN WAN 8
Local area network (LAN) Confined to a relatively small space, such as a building or an office. Usually spans about 0-5kms and is generally a private network owned by an organization. Each computer has the potential to communicate with any other computer of the network. High degree of interconnection between computers Easy physical connection of computers in a network. Inexpensive medium of data transmission. High data transmission rate. Local area network (LAN) 9
Metropolitan Area Network Larger than a LAN; connects clients and servers from multiple buildings Is used to describe a network of computers spanning a metropolitan city usually 5-50 kms of range. A company having multiple offices in various parts of a city generally uses this type of network. Example is the cellular or mobile phone network. Metropolitan Area Network 10
Wide area network (WAN) Connects two or more geographically distinct LANs or MANs Communication facility Remote data entry Centralised information The transmission medium used is normally telephone lines, microwaves and satellite links. Internet is an example of a wan Wide area network (WAN) 11
The differences between LAN and WAN LAN Restricted to limited geographical area of few kilometres Devices are connected with wires and coaxial cables Cost of data transmission in LAN is less The speed of data transmission is much higher in LAN than in WAN. The speed varies from 0.1 to 100 mbps Few data transmission errors occur in LAN compared to WAN. WAN Covers long distance and operates nationwide or even worldwide Communication is done through telephone lines and satellite links Cost of data transmission is very high WAN the speed ranges from 1800 to 9600 bps. More data transmission errors occur in WAN compared to LAN. Client Workstation Network Interface Card (NIC) Server Node Host Elements Common to Client/Server Networks Topology Network Operating System (NOS) Segment Transmission Media Connectivity device 12
Server A computer on the network that manages shared resources; servers usually have more processing power, memory, and hard disk space than clients. They run network operating software that can manage not only data, but also users, groups, security, and applications on the network. Client A computer on the network that requests resources or services from another computer on a network; in some cases, a client could also act as a server. The term client may also refer to the human user of a client workstation or to client software installed on the workstation. 13
Workstation A personal computer (such as a desktop or laptop), which may or may not be connected to a network; most clients are workstation computers. Host A computer that enables resource sharing by other computers on the same network 14
Node A client, server, or other device that can communicate over a network and that is identified by a unique number, known as its network address. Segment A part of a network. Usually, a segment is composed of a group of nodes that use the same communications channel for all their traffic. 15
Connectivity Device A specialized device that allows multiple networks or multiple parts of one network to connect and exchange data. A client/server network can operate without connectivity devices. However, medium- and large-sized LANs use them to extend the network and to connect with WANs. 16
Topology The physical layout of a computer network. Topologies vary according to the needs of the organization and available hardware and expertise. Networks can be arranged in a ring, bus, or star formation, and the star formation is the most common. Hybrid combinations of these patterns are also possible. 17
Transmission Media The means through which data is transmitted and received. Transmission media may be physical, such as wire or cable, or atmospheric (wireless), such as radio waves. 18
Network Interface Card The device inside a computer that connects a computer to the network media, thus allowing it to communicate with other computers; Some connect to the motherboard, which is the main circuit that controls the computer, some are integrated as part of the motherboard, and others connect via an external port. NICs are also known as network adapters. 19
Network Operating System The software that runs on a server and enables the server to manage data, users, groups, security, applications, and other networking functions. Examples include various types of UNIX and Linux operating systems, Microsoft Windows Server 2003 or Windows Server 2008, and Mac OS X Server. 20
Network Topology Bus Ring Star Hybrid Star Wired Bus Star Wired Ring 21
Bus In bus topology all workstations are connected to a single communication line called bus. In this type of network topology there is no central server and all the computers can talk or communicate to all other systems connected to the cable. Transmission from any station travels the length of the bus in both directions and can be received by all workstations. 22
Ring In ring topology each station is attached to nearby stations on a point-to-point basis so that the entire system is in the form of a ring. In this topology data is transmitted in one direction only. Thus the data packets circulate along the ring in either clockwise or anticlockwise direction. 23
Star In star topology a number of workstations (or nodes) are directly linked to a central server. Any communication between stations in a star LAN must pass through the central server. There is bi-directional communication between various nodes. The central server controls all the activities of the nodes. 24
Hybrid A complex combination of the basic topologies is known as a hybrid topology. A hybrid is a combination of two or more basic network topologies, such as a star-bus, star-ring, or tiered topology. In a hybrid topology, central and distributed topologies are combined to meet the needs of an organization. 25
Hybrid Star Wired Bus In a star-wired bus topology, groups of workstations are star-connected to connectivity devices and then networked via a single bus, Star Wired Ring The star-wired ring topology uses the physical layout of a star in conjunction with the ring logical topology. Hybrid Star Wired Bus Star Wired Ring 26
Network Topologies Bus Star Ring All devices are connected to a central cable, called the bus or backbone. Bus networks are relatively inexpensive and easy to install for small networks. All devices are connected to a central device, called a hub. Star networks are relatively easy to install and manage, but bottlenecks can occur because all data must pass through the hub. All devices are connected to one another in the shape of a closed loop, so that each device is connected directly to two other devices, one on either side of it. Ring topologies are relatively expensive and difficult to install, but they offer high bandwidth and can span large distances. Hybrid Groups of star-configured workstations are connected to a linear bus backbone cable, combining the characteristics of the bus and star topologies. 1. ANSI 2. EIA/TIA 3. IEEE 7. ICANN The Networking Standards 6. ISOC 5. ITU 4. ISO 27
ANSI American National Standards Institute (ANSI) Composed of more than a thousand representatives from industry and government Represents United States in setting international standards ANSI standards documents available: ANSI s Web site (www.ansi.org) At university or public libraries EIA and TIA Electronic Industries Alliance (EIA): Trade organization composed of representatives from electronics manufacturing firms across US Sets standards for its members Helps write ANSI standards Lobbies for legislation favorable to growth of computer and electronics industries Telecommunications Industry Association (TIA): Focuses on standards for information technology (IT), wireless, satellite, fiber optics, and telephone equipment 28
IEEE Institute of Electrical and Electronics Engineers International society composed of engineering professionals Goals are to promote development and education in electrical engineering and computer science IEEE technical papers and standards are highly respected in the networking profession Can purchase IEEE documents online from IEEE s Web site (www.ieee.org) ISO International Organization for Standardization Collection of organization standards representing 146 countries Goal is to establish international technological standards to facilitate global exchange of information and barrier-free trade Fewer than 300 of ISO s more than 14,250 standards apply to computer-related products and functions 29
ITU International Telecommunication Union Regulates international telecommunications: Radio and TV frequencies Satellite and telephony specifications Networking infrastructure Tariffs applied to global communications Typically, documents pertain more to global telecommunications issues than to industry technical specifications ISOC Internet Society Professional membership society that helps to establish technical standards for the Internet Oversees groups with specific missions: Internet Architecture Board (IAB): Technical advisory group of researchers and professionals Interested in overseeing Internet s design and management Internet Engineering Task Force (IETF): Sets standards for how systems communicate over the Internet How protocols operate and interact 30
IANA and ICANN Internet Protocol (IP) addresses: Addresses used to identify computers on the Internet and other TCP/IP-based networks Internet Assigned Numbers Authority (IANA): Used to keep records of available and reserved IP addresses and determines how addresses were doled out In 1997, coordinated efforts with three Regional Internet Registries (RIRs) Not-for-profit agency that manages distribution of IP addresses to private and public entities IANA and ICANN (continued) In late 1990s U.S. Department of Commerce (DOC) overhauled IP addressing and domain name management Internet Corporation for Assigned Names and Numbers (ICANN): Ultimately responsible for IP addressing and domain name management IANA still performs system administration Individuals and businesses lease addresses from Internet Service Provider (ISP) Business providing access to Internet and other services 31
2. The rules 3. Terminologies 1. Basic Elements Principles of communication in networking 4. Communication problem Basic Elements of a Communication System Source Channel Destination 32
Basic Elements of a Communication System Source This device generates the data to be transmitted; examples are telephones and personal computers. Channel A medium that carries the message. Destination The receiver (sink) who receives the message Rules of communications between two points Computer Based Device 1 Transmission Medium Computer Based Device 2 There are a number of phases that both devices must pass through in order to perform the common communications function of file transfer These phases ensure that the software on each device is structured to correct for errors or inconsistencies from the corresponding, remote device. 33
Rules of communications between two points The rules for each of these phases are clearly defined by a protocol and typical phases are as follows: Establish a link Issue a command and command qualifier Acknowledgment of command Dissection messages Error detection and correction Termination of transmission Establish a link Device 1 checks to see if Device 2 is present on the link by sending a specific "enquiry" message. If the link is active and device 2 is active then it should respond by sending back an "acknowledgement" message. Device 1 must track the time that device 2 takes to respond. If device 2 does not respond within a time interval (defined by the protocol) then device 1 assumes that the link is not active. This is called a transmission "time-out" error 34
Issue a command and command qualifier Device 1 sends device 2 a message, in a predefined format, which tells device 2 that a file is to be transferred. As a qualifier within the message, device 1 tells device 2 what to do with the file. For example, device 1 may tell device 2 to place the incoming file onto disk storage, with the file-name "FRED". Acknowledgment of command If device 2 has correctly received the command and qualifier from device 1, and is capable of carrying out the command, then it sends device 1 an acknowledgement message. The acknowledgement message tells device 1 that it can now proceed with further action needed to fulfil the command. If device 2 is unable to act upon the command from device 1, then it must respond with an error message. 35
Acknowledgment of command An error could occur on the receiver if, for example, the disk on which the incoming file is to be stored, is already full. The error response message would tell device 1 that it should not proceed with its proposed course of action. Dissection messages All messages, command and otherwise, must be broken down into packets of manageable size for transmission. Thus if an error should occur in a packet, then only that packet needs to be re-transmitted (and not the entire message). Therefore, when device 1 wishes to transfer a large file to device 2, the file is broken up into packets and transmitted packet by packet. 36
Error detection and correction When device 1 sends a message packet to device 2, it performs a mathematical calculation (manipulation) on every unit of data transmitted. This calculation is transmitted to device 2 immediately after the message. Device 2 performs exactly the same mathematical calculation on its incoming data as device 1. Error detection and correction Device 2 also reads in the calculation sent by device 1 and compares it with the local calculation. If the two calculations provide an identical result, then it is assumed that the incoming message was not corrupted on the link. Device 2 can then issue a positive acknowledgement to device 1 to indicate that it is ready for the next message. If the two calculations are inconsistent, then it is assumed that incoming data has been corrupted, and device 2 issues a "negative acknowledgement" message to device 1, which indicates that the previous data message must be re-transmitted. 37
Termination of transmission Device 1 transmits a file, piece-wise, ensuring that each packet is correctly received by device 2, using the technique described in (Error Detection and Correction). After the last piece of the file is transmitted to device 2 and positively acknowledged, then device 1 must terminate the transmission. Device 1 sends an "end of transmission" message to device 2. This allows device 2 to close the stored file and return to other duties. Terminologies in relation to communication in networking Message Encoding The effect of the skills, attitudes, and knowledge of the sender on the process of encoding the message. Message Formatting A matter of agreement between two parties as to the form of the data to be exchanged or transmitted. For example, both sides must use the same binary code for characters. 38
Terminologies in relation to communication in networking Message Size the physical dimensions and proportions of message. Message Timing Includes speed matching and sequencing of message Message Patterns Patterns of messages occur in two distinct forms: messages between objects, called a Protocol, and messages understood by a particular kind of object, called an Interface. Communication problem Contract Pattern Problem: How can behaviours be defined independent of implementations? Correlation Identifier Problem: In any messaging system, a consumer might send several message requests to different service providers. Message Sequence Problem: Because of the inherent distributed nature of messaging, communication generally occurs over a network. Message Expiration Problem: Messages are stored on disk or persistent media. With the growing number of messages, disk space is consumed. 39
Networking Hardware Types of network interface card Install and configure NIC hardware and software. Functions of LAN connectivity hardware. Build simple peer-to-peer network using TIA/EIA-568-a or TIA/EIA-568-b wiring standard. Types Of Network Interface Card Cards on an expansion board inside a computer (PCI NIC, PCI Express NIC). It is used to connect Fast Ethernet Networks together and it is connected to a PCI Slot located on your computer's Motherboard Cards installed to the computer s bus externally (PCMCIA adapter, USB port, FireWire, Compact Flash NIC) PCMCIA (Personal Computer Memory Card International Association), USB (universal serial bus), CompactFlash, or FireWire (IEEE 1394) slots can all be used to connect peripherals such as NICs. One advantage to externally attached NICs is their simple installation. 40
Types Of Network Interface Card On-board NIC A NIC that is integrated into a computer s motherboard, rather than connected via an expansion slot or peripheral bus. Not all peripheral devices are connected to a computer s motherboard via an expansion slot or peripheral bus. Some are connected directly to the motherboard using on-board ports. For example, the electrical connection that controls a computer s mouse operates through an on-board port, as does the connection for its keyboard and monitor. Types Of Network Interface Card Wireless NIC NICs are designed for use with either wired or wireless networks. Wireless NICs, which contain antennas to send and receive signals. One disadvantage to using wireless NICs is that currently they are somewhat more expensive than wire-bound NICs using the same bus type 41
Functions of LAN connectivity hardware Repeater Hub / Switch Bridges Routers Gateways Repeater Since a signal loses strength as it passes along a cable, it is often necessary to boost the signal with a device called a repeater. The repeater electrically amplifies the signal it receives and rebroadcasts it. Repeaters can be separate devices or they can be incorporated into a concentrator. 42
Hub / Switch A concentrator is a device that provides a central connection point for cables from workstations, servers, and peripherals. In a star topology, twisted-pair wire is run from each workstation to a central switch/hub. Most switches are active, that is they electrically amplify the signal as it moves from one device to another. Hub / Switch Switches no longer broadcast network packets as hubs did in the past, they memorize addressing of computers and send the information to the correct location directly. 43
Bridges A bridge is a device that allows you to segment a large network into two smaller, more efficient networks. If you are adding to an older wiring scheme and want the new network to be up-to-date, a bridge can connect the two. A bridge monitors the information traffic on both sides of the network so that it can pass packets of information to the correct location. Bridges Most bridges can "listen" to the network and automatically figure out the address of each computer on both sides of the bridge. The bridge can inspect each message and, if necessary, broadcast it on the other side of the network. The bridge manages the traffic to maintain optimum performance on both sides of the network 44
Routers Router is intelligent device which routes data to destination computers. It helps in connecting two different logical and physical networks together. In small network server is connected to router along with clients for communication. With routers network communication is not possible; it is soul of network without which distribution if internet and other network data to entire network are impossible. Routers 45
Gateways As name suggests it some kind of passing through to something. Interestingly gateways can be software or it can also be device. Gateway device connects LAN with internet. Its basic functionality is to provide security to the network. By using gateways incoming/out going traffic can be monitored for any malicious activity within the network which can be harmful to network integrity. 46
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