Network fundamentals
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The document discusses networking fundamentals, highlighting the significant role of networks in education, business, and recreation, as well as the technological advancements that facilitate these networks. It defines types of networks, network components, and standards, and introduces network models such as the OSI and TCP/IP models, detailing their respective layers and functions. Additionally, it touches on the importance of protocols in ensuring effective communication across different network types.
Network fundamentals
- 1. 1 1.0 Networking Fundamentals 1.1 INTRODUCTION Networking fundamentals teaches the building blocks of modern network design. Learn different types of networks, concepts, architecture and design. Typically you will learn about the many different types of networks, networking concepts, network architecture, network communications and network design. NETWORKS SUPPORTING THE WAY WE LEARN The advances in the Internet and collaboration tools have been the force behind major changes in education. As web reliability and access have increased, more institutions have come to depend on technology to perform core educational functions. For example, distance education was once limited to correspondence, videos, or video and audio conferences. With newer collaboration tools and stronger web technologies, online learning can engage remote students in interactive learning and real-time assessment. The classes can use document sharing, wikis, online video, and online testing software to enhance learning opportunities. Student learning is becoming less dependent on location and schedule, which opens courses to potential students who previously could not attend classes. The methods of both face-to-face and online instruction are changing with the introduction of web tools such as wikis. Traditionally, a teacher provided course content and the class might have benefited from some discussions. With online tools equally available to all students, many classes focus on sharing the opinions and expertise of students. This is a significant change for many students and instructors, but it is an example of the impact of technical change on society’s traditions. The administration side of instruction has also changed. You might have enrolled in this course on the web and paid with an online bank account. Your final grades might be posted on a school website, and you might never have a face-to-face meeting with your advisor. This is the business side of education, and it is changing as new management tools become available.
- 2. 2 NETWORKS SUPPORTING THE WAY WE WORK Advances in computer networks have had a tremendous impact on businesses. Many economists attribute much of the economic growth of the past couple of decades to increased productivity in business stemming from improved business technologies. Many companies use collaboration software packages that allow distributed work groups— people working together but not in the same physical location—to interactively create documents and contribute to projects in real time. These collaboration tools demonstrate the global nature of online business and are now essential to large and small businesses alike. Different companies use different types of networks. Employees can meet on the Internet, or they can join a restricted group on a company intranet, which allows only internal employee access. Another type of network is an extranet, a type of network that allows outside vendors special access to limited information in a company. To reap the benefits of these technology tools, businesses must provide the continuing training and education of workers. The ability to learn and adopt new ways to implement technology into the workplace is a valuable skill sought after by most employers. Most of the preceding examples highlight the benefits that larger corporations experience from computer networks. Networks also have enabled small businesses to achieve success. NETWORKS SUPPORTING THE WAY WE PLAY You have learned how networks provide learning and business opportunities, but they offer plenty of recreation options as well. Travel sites can respond to last-minute market conditions for hotel, flight, and cruise availability, which benefits both sellers and consumers. Media and entertainment companies provide websites that offer books, games, TV shows, and movies. The music industry provides songs for download. While the web has helped the music industry reach new audiences and cut costs, record companies have also faced new challenges, such as music-sharing sites and copyright issues. Online auction sites provide an excellent venue for hobbyists and collectors to exchange information and items safely and securely. Some of the most innovative developments in network technology come about trying to satisfy the voracious appetite of the entertainment sector. Online game companies are constantly pushing for better bandwidth and faster processing to improve their products, and online gamers are willing to spend the money necessary to buy the latest equipment that will improve their gaming experience. Movie rentals and video-sharing and distribution systems are newer web technologies that are quickly evolving as faster web connections become more widespread.
- 3. 3 1.2 Defining a Network A network is a group of two or more computer systems or other devices that are linked together to exchange data. Networks share resources, exchange files and electronic communications. For example, networked computers can share files or multiple computers on the network can share the same printer. 1.3 Different Types of Networks There are many types of computer networks. Common types of networks include the following: Local-area network (LAN): The computers are geographically close together (that is, in the same building). Wide-area network (WAN): The computers are farther apart and are connected by telephone lines or radio waves. Metropolitan-area network (MAN): A data network designed for a town or city. Home-area network (HAN): A network contained within a user's home that connects a person's digital devices. Virtual private network (VPN): A network that is constructed by using public wires — usually the Internet — to connect to a private network, such as a company's internal network. Storage area network (SAN): A high-speed network of storage devices that also connects those storage devices with servers. 2.0 The Importance of Network Standards Network standards are important to ensure that hardware and software can work together. Without standards you could not easily develop a network to share information. Networking standards can be categorized in one of two ways: formal and de facto (informal). Formal standards are developed by industry, organizations or governments. Formal standards exist for network layer software, data link layer, hardware and so on. Formal standardization is a lengthy process of developing the specification, identifying choices and industry acceptance. There are a several leading organizations for standardization including The International Organization for Standardization (ISO) and The American National Standards Institute (ANSI). The most known standards organization in the world is the Internet Engineering Task Force (IETF). IETF sets the standards that govern how much of the Internet operates. The second category of networking standards is de facto standards. These standards typically emerge in the marketplace and are supported by technology vendors but have no official
- 4. 4 backing. For example, Microsoft Windows is a de facto standard, but is not formally recognized by any standards organization. It is simply widely recognized and accepted. 2.1 Network Components, Devices and Functions Networks share common devices and functions, such as servers, transmission media (the cabling used to connect the network) clients, shared data (e.g. files and email), network cards, printers and other peripheral devices. The following is a brief introduction to common network components and devices. Server: A computer or device on a network that manages network resources. Servers are often dedicated, meaning that they perform no other tasks besides their server tasks. Client: A client is an application that runs on a personal computer or workstation and relies on a server to perform some operations. Devices: Computer devices, such as a CD-ROM drive or printer that is not part of the essential computer. Examples of devices include disk drives, printers, and modems. Transmission Media: the type of physical system used to carry a communication signal from one system to another. Examples of transmission media include twisted-pair cable, coaxial cable, and fiber optic cable. Network Operating System (NOS): A network operating system includes special functions for connecting computers and devices into a local-area network (LAN). The term network operating system is generally reserved for software that enhances a basic operating system by adding networking features. Operating System: Operating systems provide a software platform on top of which other programs, called application programs, can run. Operating systems perform basic tasks, such as recognizing input from the keyboard, sending output to the display screen, keeping track of files and directories on the disk, and controlling peripheral devices such as disk drives and printers. Network Interface Card (NIC): An expansion board you insert into a computer so the computer can be connected to a network. Most NICs are designed for a particular type of network, protocol, and media, although some can serve multiple networks. Hub: A common connection point for devices in a network. A hub contains multiple ports. When a packet arrives at one port, it is copied to the other ports so that all segments of the LAN can see all packets.
- 5. 5 Switch: A device that filters and forwards packets between LAN segments. Switches operate at the data link layer (layer 2) and sometimes the network layer (layer 3) of the OSI Reference Model. Router: A router is a device that forwards data packets along networks. A router is connected to at least two networks and is located at gateways, the places where two or more networks connect. Gateway: A node on a network that serves as an entrance to another network. Bridge: A device that connects two local-area networks (LANs), or two segments of the same LAN that use the same protocol Channel Service Unit/Digital Service Unit (CSU/DSU): The CSU is a device that connects a terminal to a digital line. Typically, the two devices are packaged as a single unit. Terminal Adapter (ISDN Adapter): A device that connects a computer to an external digital communications line, such as an ISDN line. A terminal adapter is a bit like a modem but only needs to pass along digital signals. Access Point: A hardware device or a computer's software that acts as a communication hub for users of a wireless device to connect to a wired LAN. Modem (modulator-demodulator): A modem is a device or program that enables a computer to transmit data over, for example, telephone or cable lines. Firewall: A system designed to prevent unauthorized access to or from a private network. Firewalls can be implemented in both hardware and software, or a combination of both. MAC Address: A MAC (Media Access Control) address, sometimes referred to as a hardware address or physical address is an ID code that's assigned to a network adapter or any device with built-in networking capability. IP phone: A digital telephone that carries voice as data over data networks instead of analog phone lines. 3.0 Network Models To simplify networks, everything is separated in layers and each layer handles specific tasks and is independent of all other layers. Control is passed from one layer to the next, starting at the top layer in one station, and proceeding to the bottom layer, over the channel to the next station and back up the hierarchy. Network models are used to define a set of network layers and how they interact. The two most widely recognized network models include the TCP/IP
- 6. 6 Model and the OSI Network Model. The standardization of the various elements of the network enables equipment and devices created by different companies to work together. Experts in various technologies can contribute their best ideas on how to develop an efficient network, without regard to the brand or manufacturer of the equipment. 3.1 The 7 Layers of the OSI Model The Open System Interconnect (OSI) is an open standard for all communication systems. The OSI model defines a networking framework to implement protocols in seven layers. There 7 types of OSI Model. The layers include the following: Physical Layer This layer conveys the bit stream - electrical impulse, light or radio signal -- through the network at the electrical and mechanical level. It provides the hardware means of sending and receiving data on a carrier, including defining cables, cards and physical aspects. Examples include Ethernet, FDDI, B8ZS, V.35, V.24, and RJ45. Data Link Layer At this layer, data packets are encoded and decoded into bits. It furnishes transmission protocol knowledge and management and handles errors in the physical layer, flow control and frame synchronization. The data link layer is divided into two sub layers: The Media Access Control (MAC) layer and the Logical Link Control (LLC) layer. Examples include PPP, FDDI, ATM, and IEEE 802.5 / 802.2, IEEE 802.3/802.2, HDLC, and Frame Relay. Network Layer This layer provides switching and routing technologies, creating logical paths, known as virtual circuits, for transmitting data from node to node. Routing and forwarding are functions of this layer, as well as addressing, internetworking, error handling, congestion control and packet sequencing. Examples include AppleTalk DDP, IP and IPX. Transport Layer This layer provides transparent transfer of data between end systems, or hosts, and is responsible for end-to-end error recovery and flow control. It ensures complete data transfer. Examples include SPX, TCP and UDP.
- 7. 7 Session Layer This layer establishes, manages and terminates connections between applications. The session layer sets up, coordinates, and terminates conversations, exchanges, and dialogues between the applications at each end. Examples include NFS, NetBIOS names, RPC, SQL. Presentation Layer This layer provides independence from differences in data representation (e.g., encryption) by translating from application to network format, and vice versa. This layer formats and encrypts data to be sent across a network, providing freedom from compatibility problems. Examples include encryption, ASCII, EBCDIC, TIFF, GIF, PICT, JPEG, MPEG, and MIDI. Application Layer This layer supports application and end-user processes. Communication partners are identified, quality of service is identified, user authentication and privacy are considered, and any constraints on data syntax are identified. Everything at this layer is application-specific. This layer provides application services for file transfers, e-mail, and other network software services. Examples include WWW browsers, NFS, SNMP, Telnet, HTTP, and FTP Networking Rules All communication processes happen, as far as humans can tell, in an instant, and tens of thousands of processes can happen in a single second. To work properly, the network processes must be tightly controlled. Rules govern every step of the process, from the way cables are designed to the way the digital signals are sent. These rules are called protocols, and the communications industry has standardized most of them to allow people in different places with different equipment to communicate. The most common protocols are IP (Internet Protocol) and TCP (Transmission Control Protocol). These protocols work together and are usually known as the TCP/IP protocol stack. TCP/IP works along other protocols, for example, Extensible Messaging and Presence Protocol (XMPP), which is an instant messaging protocol, to provide communication rules involving different services. The list of some common services and the protocols that support them are: World Wide Web (WWW), HTTP (Hypertext Transport Protocol), E-mail-SMTP (Simple Mail Transport Protocol), and POP (Post Office Protocol), Instant message XMPP (Extensible Messaging and Presence Protocol), and (Jabber, AIM) OSCAR (Open System for Communication in Real-time)
- 8. 8 IP telephony-SIP (Session Initiation Protocol). People often only picture networks in the abstract sense. Communications Flow on Network People often only picture networks in the abstract sense: We create and send a text message, and it almost immediately shows up on the destination device. Although we know that between our sending device and the receiving device there is a network over which our message travels, we rarely think about all the parts and pieces that make up that infrastructure. The following list ties together how the elements of networks—devices, media, and services—are connected by rules to deliver a message: 1. An end user types an instant message to a friend using an application on a PC. 2. The instant message gets converted into a format that can be transmitted on the network. All types of message format—text, video, voice, or data—must be converted to bits before being sent to their destinations. After the instant message is converted to bits, it is ready to be sent onto the network for delivery. 3. The network interface card (NIC) inside the PC generates electrical signals to represent the bits and places the bits on the medium so that they can travel to the first network device. 4. The bits are passed from device to device in the local network. 5. If the bits need to leave the local network, they leave through a router connecting to a different network. There can be dozens, even hundreds, of devices handling the bits as they are routed to their destination. 6. As the bits get close to their destination, they once again get passed through local devices. 7. Finally, the NIC on the destination device accepts the bits and converts them back into a readable text message. 3.2 The TCP/IP model The TCP/IP network model is a four-layer reference model. All protocols that belong to the TCP/IP protocol suite are located in the top three layers of this model.
- 9. 9 Application Defines TCP/IP application protocols and how host programs interface with transport layer services to use the network. Protocol examples include HTTP, Telnet, FTP, TFTP, SNMP, DNS, and SMTP. Transport Provides communication session management between host computers. Defines the level of service and status of the connection used when transporting data. Protocol examples include TCP, UDP, and RTP. Internet Packages data into IP datagrams, which contain source and destination address information that is used to forward the datagrams between hosts and across networks. Performs routing of IP datagrams. Protocol examples include IP, ICMP, ARP, and RARP. Network interface Specifies details of how data is physically sent through the network, including how bits are electrically signaled by hardware devices that interface directly with a network medium, such as coaxial cable, optical fiber, or twisted-pair copper wire. Protocol examples include Ethernet, Token Ring, FDDI, X.25, Frame Relay, RS-232, v.35. Each layer of the TCP/IP model corresponds to one or more layers of the seven-layer Open Systems Interconnection (OSI) reference model. 3.3 Network Topologies Network topology refers to the shape or the arrangement of the different elements in a computer network (i.e. links and nodes). Network Topology defines how different nodes in a network are connected to each other and how they communicate is determined by the network's topology. Topologies are either physical or logical. There are four principal topologies used in LANs. Bus Topology 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.
- 10. 10 Ring Topology 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. Star Topology All devices are connected to a central hub. Star networks are relatively easy to install and manage, but bottlenecks can occur because all data must pass through the hub. Tree Topology A tree topology combines characteristics of linear bus and star topologies. It consists of groups of star-configured workstations connected to a linear bus backbone cable. These topologies can also be mixed. For example, a bus-star network consists of a high- bandwidth bus, called the backbone, which connects collections of slower-bandwidth star segments.