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Computer Networks Laboratory 907528 Lab 0: Introduction to Networks lab University of Jordan Faculty of Engineering & Technology Computer Engineering Department Computer Networks Laboratory 907528 1 Lab 0: Introduction to Networks lab Introduction to Networking By themselves, computers are powerful tools. When they are connected in a network, they become even more powerful because the functions and tools that each computer provides can be shared with other computers. Network is a small group of computers that share information, or they can be very complex, spanning large geographical areas that provide its users with unique capabilities, above and beyond what the individual machines and their software applications can provide. The goal of any computer network is to allow multiple computers to communicate. The type of communication can be as varied as the type of conversations you might have throughout the course of a day. For example, the communication might be a download of an MP3 audio file for your MP3 player; using a web browser to check your instructor’s web page to see what assignments and tests might be coming up; checking the latest sports scores; using an instant- messaging service, such as Yahoo Messenger, to send text messages to a friend; or writing an e- mail and sending it to a business associate. Networks Advantages and Disadvantages: -Network Hardware, Software and Setup Costs. -Hardware and Software Management & Administration Costs. -Undesirable Sharing. -Illegal or Undesirable Behavior. -Data Security Concerns. -Connectivity and Communication. -Data SharingHardware Sharing. -Internet Access. -Data Security and Management. -Performance Enhancement and Balancing. -Entertainment. 2 Lab 0: Introduction to Networks lab Network Types: Different types of networks are distinguished based on their size (in terms of the number of machines), their data transfer speed, and their reach. There are usually said to be two categories of networks: Local Area Network (LAN)is limited to a specific area, usually an office, and cannot extend beyond the boundaries of a single building. The first LANs were limited to a range (from a central point to the most distant computer) of 185 meters (about 600 feet) and no more than 30 computers. Today’s technology allows a larger LAN, but practical administration limitations require dividing it into small, logical areas called workgroups. A workgroup is a collection of individuals who share the same files and databases over the LAN. Wide Area Network (WAN)If you have ever connected to the Internet, you have used the largest WAN on the planet. A WAN is any network that crosses metropolitan, regional, or national boundaries. Most networking professionals define a WAN as any network that uses routers and public network links. The Internet fits both definitions. 3 Lab 0: Introduction to Networks lab LAN WAN Definition: LAN (Local Area Network) is a WAN (Wide Area Network) is a computer network covering a computer network that covers a small geographic area, like a broad area or any network whose home, office, schools, or group communications links cross of buildings. metropolitan, regional, or national boundaries over a long distance. Speed: High speed(1000mbps) Less speed(150mbps) Data transfer High data transfer rate. Lower data transfer rate as rates: compared to LANs. Example: Network in an organization. The Internet. Components: Layer 2 devices like switches, Layers 3 devices Routers, bridges. layer1 devices like Switches and Technology specific hubs , repeaters devices like ATM or Frame-relay Switches. Data Transmission Experiences fewer data Experiences more data Error: transmission errors. transmission errors as compared to LAN. Ownership: Typically owned, controlled, WANs (like the Internet) are not and managed by a single person owned by any one organization or organization. but rather exist under collective distributed ownership and management over long distances. Set-up costs: Set-up an extra devices on the Networks in remote areas have to network, it is not very be connected, Set-up costs are expensive. higher. Maintenance costs: Covers a relatively small Maintaining WAN is difficult geographical area, LAN is because of its wider geographical easier to maintain at coverage and higher maintenance relatively low costs. costs. Geographical Have a Have a large geographical range Spread: small geographical range. generally spreading across boundaries. Bandwidth: High bandwidth is available for Low bandwidth is available for transmission. transmission. The OSI and TCP/IP Networking Models: Models are useful because they help us understand difficult concepts and complicated systems. When it comes to networking, there are several models that are used to explain the roles played by various technologies, and how they interact. Of these, the most popular and commonly used is the Open Systems Interconnection (OSI) Reference Model. 4 Lab 0: Introduction to Networks lab The OSI model was designed to promote interoperability by creating a guideline for network data transmission between computers and components that have different hardware vendors, software, operating systems, and protocols. The idea behind the OSI Reference Model is to provide a framework for both designing networking systems and for explaining how they work. The existence of the model makes it easier for networks to be analyzed, designed, built and rearranged, by allowing them to be considered as modular pieces that interact in predictable ways, rather than enormous, complex monoliths. TCP/IP Model The Internet Protocol Suite, popularly known as the TCP/IP model, is a communication protocol that is used over the Internet. This model divides the entire networking functions into layers, where each layer performs a specific function. This model gives a brief idea about the process of data formatting, transmission, and finally the reception. Each of these functions takes place in the layers, as described by the model. TCP/IP is a four-layered structure, with each layer having their individual protocol. 5 Lab 0: Introduction to Networks lab Both the TCP/IP and OSI model work in a very similar fashion. But they do have very subtle differences too. The most apparent difference is the number of layers. TCP/IP is a four-layered structure, while OSI is a seven-layered model. Why Use a Layered Model? By using a layered model, we can categorize the procedures that are necessary to transmit data across a network. First, we need to define the term protocol: is a set of guidelines or rules of communication. Layered modeling allows us to: • Create a protocol that can be designed and tested in stages, which, in turn, reduces the complexity • Enhance functionality of the protocol without adversely affecting the other layers • Provide multivendor compatibility • Allow for easier troubleshooting by locating the specific layer causing the problem 6 Lab 0: Introduction to Networks lab OSI model divides the network into seven layers and explains the routing of the data from source to destination. It is a theoretical model which explains the working of the networks. Here are the details of OSI's seven layers: Application Layer (Layer 7) The Application layer is a buffer between the user interface (what the user uses to perform work) and the network application. This layer responsible for finding a communication partner on the network. Once a partner is found, it is then responsible for ensuring that there is sufficient network bandwidth to deliver the data. This layer may also be responsible for synchronizing communication and providing high level error checking between the two partners. This ensures that the application is either sending or receiving, and that the data transmitted is the same data received. Typical applications include a client/server application (Telnet), an e- mail application (SMTP), and an application to transfer files using FTP or HTTP. Presentation Layer (Layer 6) The Presentation layer is responsible for the presentation of data to the Application layer. This presentation may take the form of many structures. Data that it receives from the application layer is converted into a suitable format that is recognized by the computer. Perform conversion between ASCII and EBCDIC (a different character formatting method used on many mainframes). The Presentation layer must ensure that the application can view the appropriate data when it is reassembled. Graphic files such as PICT, JPEG, TIFF, and GIF, and video and sound files such as MPEG and Apple’s QuickTime are examples of Presentation layer responsibilities. One final data structure is data encryption. Sometimes, it is vital that we can send data across a network without someone being able to view our data, or snoop it. 7 Lab 0: Introduction to Networks lab Session Layer (Layer 5) The Session layer sets up and terminates communications between the two partners. Thislayer decides on the method of communication: half-duplex or full-duplex. Full-Duplex vs. Half-Duplex Communications All network communications (including LAN and WAN communications) can be categorized as Half-duplex or full-duplex. With half-duplex, communications happen in both directions, but in only one direction at a time. When two computers communicate using half-duplex, one computer sends a signal and the other receives; then, at some point, they switch sending and receiving roles. Full-duplex, on the other hand, allows communication in both directions simultaneously. Both stations can send and receive signals at the same time. Full-duplex communications are similar to a telephone call, in which both people can talk simultaneously. 8 Lab 0: Introduction to Networks lab Transport Layer (Layer 4) This layer provides end-to-end delivery of data between two nodes. It divides data into different packets before transmitting it. On receipt of these packets, the data is reassembled and forwarded to the next layer. If the data is lost in transmission or has errors, then this layer recovers the lost data and transmits the same. Transport layer add port number and sequence number to assemble and distinguish between multiple applications segments received at a device; this also allows data to be multiplexed on the line.
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