The Network Essentials

Published Date: 02 Nov 2017

A computer network, or just a network, is a collection of computers and other hardware are interconnected by communication channels that allow sharing of resources and information. If at least one process in one device is able to send / receive data to / least one process residing in a remote device, then the two devices in the network said. Network is a group of devices that are connected to each other. Networks can be classified into a range of features: the medium used to transport the data, communications protocol used, scale, topology, benefits, and scope of the organization.

Communication protocols to determine rules and data formats for exchanging information in a computer network, and provide a basis for network programming. Well-known communications protocols including two Ethernet, hardware layer and link the ubiquitous standard in local area networks, and the Internet protocol suite, which defines a set of protocols for internetworking, i.e. for data communication between multiple networks, as well as host-to-host transfer data, and application-specific data transmission formats.

The computer network is sometimes regarded as a sub-discipline of telecommunications engineering, electrical, computer science, information technology or computer engineering, since it relies on the theory and practical application of this discipline.

Answer

The wired network connection requires a computer to be connected to a port in the wall via an Ethernet cable, whereas the wireless network connection can be accessed without a cable. A wired network is one in which all the components are connected with network cables. Local Area Network (LAN) and Ethernet are listed as one of the example of wired network. Wireless network refers to any type of computer network that is not connected by cables of any kind .It is a method by which homes, telecommunications networks and enterprise (business) installations avoid the costly process of introducing cables into a building, or as a connection between location of various equipment.

Wired Networks

Wired and wireless networks each have advantages and disadvantages; depending on your needs, one may serve you better than the other. Wired networks provide users with plenty of security and the ability to move lots of data very quickly. Wired networks are typically faster than wireless networks, and they can be very affordable. However, the cost of Ethernet cable can add up -- the more computers on your network and the farther apart they are, the more expensive your network will be. In addition, unless you're building a new house and installing Ethernet cable in the walls, you'll be able to see the cables running from place to place around your home, and wires can greatly limit your mobility. A laptop owner, for example, won't be able to move around easily if his computer is tethered to the wall.

There are three basic systems people use to set up wired networks. An Ethernet system uses either a twisted copper-pair or coaxial-based transport system. The most commonly used cable for Ethernet is a category 5 unshielded twisted pair (UTP) cable -- it's useful for businesses who want to connect several devices together, such as computers and printers, but it's bulky and expensive, making it less practical for home use. A phone line, on the other hand, simply uses existing phone wiring found in most homes, and can provide fast services such as DSL. Finally, broadband systems provide cable Internet and use the same type of coaxial cable that gives us cable television.

If you plan to connect only two computers, all you'll need is a network interface card (NIC) in each computer and a cable to run between them. If you want to connect several computers or other devices, you'll need an additional piece of equipment: an Ethernet router. You'll also need a cable to connect each computer or device to the router.

Once you have all of your equipment, all you need to do is install it and configure your computers so they can talk to one another. Exactly what you need to do depends on the type of network and your existing hardware. For example, if your computers came with network cards already installed, all you'll need to do is buy a router and cables and configure your computers to use them. Regardless of which type you select, the routers, adapters and other hardware you buy should come with complete setup instructions.

The steps you'll need to take to configure your computers will also vary based on your hardware and your operating system. User manuals usually provide the necessary information, and Web sites dedicated to specific operating systems often have helpful tips on getting several different computers to talk to each other. Wired network can be protected from computer viruses and hackers are through firewall, anti-virus, anti-spam, spam-ware, encryption, decryption and almost all of the way can protect our computer network.

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Wireless Network

The easiest, least expensive way to connect the computers in your home is to use a wireless network, which uses radio waves instead of wires. The absence of physical wires makes this kind of network very flexible. For example, you can move a laptop from room to room without fiddling with network cables and without losing your connection. The downside is that wireless connections are generally slower than Ethernet connections and they are less secure unless you take measures to protect your network.

If you want to build a wireless network, you'll need a wireless router. Signals from a wireless router extend about 100 feet (30.5 meters) in all directions, but walls can interrupt the signal. Depending on the size and shape of your home and the range of the router, you may need to purchase a range extender or repeater to get enough coverage.

You'll also need a wireless adapter in each computer you plan to connect to the network. You can add printers and other devices to the network as well. Some new models have built-in wireless communication capabilities, and you can use a wireless Ethernet bridge to add wireless capabilities to devices that don't. Any devices that use the Bluetooth standard can also connect easily to each other within a range of about 10 meters (32 feet), and most computers, printers, cell phones, home entertainment systems and other gadgets come installed with the technology.

If you decide to build a wireless network, you'll need to take steps to protect it -- you don't want your neighbors hitchhiking on your wireless signal. Wireless security options include:

Wired Equivalency Privacy (WEP)

Wi-Fi Protected Access (WPA)

Media Access Control (MAC) address filtering

You can choose which method (or combination of methods) you want to use when you set up your wireless router. The IEEE has approved each of these security standards, but studies have proven that WEP can be broken into very easily. If you use WEP, you may consider adding Temporal Key Integrity Protocol (TKIP) to your operating system. TKIP is a wrapper with backward compatibility, which means you can add it to your existing security option without interfering with its activity. Think of it like wrapping a bandage around a cut finger -- the bandage protects the finger without preventing it from carrying out its normal functions.

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Conclusion

As the conclusion, I identified that both wired and wireless network are secured with the various ways to protect the computer network from viruses and hackers. There are also few advantages and disadvantages for the use of wired network and wireless network.

My opinion is that wireless network can be used because the cost is very low compare to the wired network since we can’t afford to buy it. The network security is also much secured and it’s safe to be used.

Question 2

The OSI, or Open System Interconnection, model defines a networking framework to implement protocols in seven layers. Explain what the 7 layers of OSI are and provide details example?

Introduction

The OSI reference model specifies standards for describing "Open Systems Interconnection" with the term 'open' chosen to emphasize the fact that by using these international standards, a system may be defined which is open to all other systems obeying the same standards throughout the world. The definition of a common technical language has been a major catalyst to the standardization of communications protocols and the functions of a protocol layer.

Answers

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1. Physical layer: Provides electrical, functional, and procedural characteristics to activate, maintain, and deactivate physical links that transparently send the bit stream; only recognizes individual bits, not characters or multicharacter frames. Physical layer defines the electrical and physical specifications for devices. In particular, it defines the relationship between the device and the transmission medium, such as copper or fiber optic cable. This includes the layout of pins, voltages, line impedance, cable specifications, signal timing, hubs, repeaters, network adapters, host bus adapters (HBA used in storage area networks) and more.

The major functions and services performed by the physical layer are establishment and termination of a connection to a communications medium. Participation in the process by which effective communication resources shared among multiple users.

For example, the debate resolution and flow control:

Modulation or conversion between the representation of digital data in user equipment and the corresponding signals transmitted over a communications channel. This is a signal to operate across physical cabling (such as copper and fiber optic) or via radio link.

Parallel SCSI buses operate in this layer, although it should be remembered that the logical SCSI protocol is a transport layer protocol that runs over this bus. Various physical layer Ethernet standards are also in this layer; Ethernet incorporates both this layer and the data link layer. The same applies to other local area networks, such as token ring, FDDI, ITU-T G.hn and IEEE 802.11, and personal area networks such as Bluetooth and IEEE 802.15.4.

2.Data link layer: Provides functional and procedural means to transfer data between network entities and (possibly) correct transmission errors; provides for activation, maintenance, and deactivation of data link connections, grouping of bits into characters and message frames, character and frame synchronization, error control, media access control, and flow control (examples include HDLC and Ethernet) The data link layer provides the functional and procedural means to transfer data between network entities and to detect and possibly correct errors that may occur in the physical layer. Originally, this layer was intended for point-to-point and point-to-multipoint media, characteristic of wide area media in the telephone system. Local area network architecture, which included broadcast-capable multi-access media, was developed independently of the ISO work in IEEE Project 802. IEEE work assumed sublayer-ing and management functions not required for WAN use. In modern practice, only error detection, not flow control using sliding window, is present in data link protocols such as Point-to-Point Protocol (PPP), and, on local area networks, the IEEE 802.2 LLC layer is not used for most protocols on the Ethernet, and on other local area networks, its flow control and acknowledgment mechanisms are rarely used. Sliding window flow control and acknowledgment is used at the transport layer by protocols such as TCP, but is still used in niches where X.25 offers performance advantages.

The ITU-T G.hn standard, which provides high-speed local area networking over existing wires (power lines, phone lines and coaxial cables), includes a complete data link layer which provides both error correction and flow control by means of a selective repeat Sliding Window Protocol.

Both WAN and LAN service arranges bits from the physical layer into logical sequences called frames. Not all physical layer bits necessarily go into frames, as some of these bits are purely intended for physical layer functions.

Following are the functions of data link layer Framing, Physical Addressing, Flow Control, Error Control, Access Control and Media Access Control (MAC)

3.Network layer: Provides independence from data transfer technology and relaying and routing considerations; masks peculiarities of data transfer medium from higher layers and provides switching and routing functions to establish, maintain, and terminate network layer connections and transfer data between users. The network layer provides the functional and procedural means of transferring variable length data sequences from a source host on one network to a destination host on a different network (in contrast to the data link layer which connects hosts within the same network), while maintaining the quality of service requested by the transport layer. The network layer performs network routing functions, and might also perform fragmentation and reassembly, and report delivery errors. Routers operate at this layer, sending data throughout the extended network and making the Internet possible. This is a logical addressing scheme – values are chosen by the network engineer. The addressing scheme is not hierarchical.

The network layer may be divided into three sublayers:

* Subnetwork access – that considers protocols that deal with the interface to networks, such as X.25; Sublayer-dependent convergence – when it is necessary to bring the level of a transit network up to the level of networks on either Sid .

Subnetwork-independent convergence – handles transfer across multiple networks.

4.Transport layer: Provides transparent transfer of data between systems, relieving upper layers from concern with providing reliable and cost effective data transfer; provides end-to-end control and information interchange with quality of service needed by the application program; first true end-to-end layer. The transport layer provides transparent transfer of data between end users, providing reliable data transfer services to the upper layers. The transport layer controls the reliability of a given link through flow control, segmentation/desegmentation, and error control. Some protocols are state- and connection-oriented. This means that the transport layer can keep track of the segments and retransmit those that fail. The transport layer also provides the acknowledgement of the successful data transmission and sends the next data if no errors occurred.

5. Session layer: Provides mechanisms for organizing and structuring dialogues between application processes; mechanisms allow for two-way simultaneous or two-way alternate operation, establishment of major and minor synchronization points, and techniques for structuring data exchanges. The session layer controls the dialogues (connections) between computers. It establishes, manages and terminates the connections between the local and remote application. It provides for full-duplex, half-duplex, or simplex operation, and establishes check pointing, adjournment, termination, and restart procedures. The OSI model made this layer responsible for graceful close of sessions, which is a property of the Transmission Control Protocol, and also for session check pointing and recovery, which is not usually used in the Internet Protocol Suite. The session layer is commonly implemented explicitly in application environments that use remote procedure calls.

6. Presentation layer: Provides independence to application processes from differences in data representation that is, in syntax selection and conversion provided by allowing the user to select a "presentation context" with conversion between alternative contexts. The presentation layer establishes context between application-layer entities, in which the higher-layer entities may use different syntax and semantics if the presentation service provides a mapping between them. If a mapping is available, presentation service data units are encapsulated into session protocol data units, and passed down the stack.

This layer provides independence from data representation (e.g., encryption) by translating between application and network formats. The presentation layer transforms data into the form that the application accepts. This layer formats and encrypts data to be sent across a network. It is sometimes called the syntax layer.

7. Application layer: Concerned with the requirements of application. All application processes use the service elements provided by the application layer. The elements include library routines which perform intercrosses communication, provide common procedures for constructing application protocols and for accessing the services provided by servers which reside on the network. The application layer is the OSI layer closest to the end user, which means that both the OSI application layer and the user interact directly with the software application. This layer interacts with software applications that implement a communicating component. Such application programs fall outside the scope of the OSI model. Application-layer functions typically include identifying communication partners, determining resource availability, and synchronizing communication. When identifying communication partners, the application layer determines the identity and availability of communication partners for an application with data to transmit. When determining resource availability, the application layer must decide whether sufficient network or the requested communication exist. In synchronizing communication, all communication between applications requires cooperation that is managed by the application layer.

Conclusion

Overall, In OSI (Open System Interconnection) model. It is basic understanding of how network works in order to troubleshoot future problem. According in seven layers each layer is functionally independent, provide services and receive services from the layers.