Monday, 11 April 2011

HND Networking Technology Assignment


What is the purpose and benefits of having a LAN network in an organization?
A local area network (LAN) is a network that is confined to a relatively small area. It is generally limited to a geographic area such as a writing lab, school, or building. LANs are reliable, high speed communication and low cost. Do not require the national telephone companies to provide communication links. Rarely are LAN computers more than a mile apart. In a typical LAN configuration, one computer is designated as the file server. It stores all of the software that controls the network, as well as the software that can be shared by the computers attached to the network. Computers connected to the file server are called workstations. The workstations can be less powerful than the file server, and they may have additional software on their hard drives. On most LANs, cables are used to connect the network interface cards in each computer. With the above definition, it shows that LAN is very popular in today’s organization and in our everyday life with the under listed benefits.
The purpose and benefits of LANs in an organization are:

• Resource sharing capability allows storage space and network peripherals, such as printers, to be shared by workstations, reducing hardware requirement, expenses and improving productivity.

• Standard PC hardware is used for network workstations and servers, which provide a great deal of design flexibility, easy maintenance and cost efficiency.

• Common applications are network aware, which significantly help in user transition time when relocating to different network environments. Additionally, network licensing is substantially less expensive than that of stand-alone licensing.

• Through file sharing, users can easily transfer files to one another, in order to improve productivity. Shared file access allows multi-user access to user applications.

• With centralized data storage, LANs offer the ability to place shared data on a single server within a central location. Network backups are easier and more reliable because all data resides on one physical location. This reduces the cost incurred by loss of any data during system failure.

• LANs support a number of fault tolerance features, such as disk mirroring, disk-duplexing, disk striping with parity (RAID5) and UPS (Uninterrupted Power Supply). This improves reliability and minimizes network downtime.

• LANs offer centralized security, which allows control over access to the network and its resources. Depending on an organization's requirements, this functionality is customizable to help protect sensitive data from loss, destruction, theft, or unauthorized disclosure.

• Communication to other users is also provided through a messaging system. It is the basis for implementing sophisticated systems

Local Areas Networks increase efficiency exponentially in an office environment. A LAN system can provide the users with an easy to use central repository of all files - increasing security and making it easier to collaborate on projects. Besides file sharing, internet access, data security and management, entertainments, performance enhancement and balancing, hardware sharing, a LAN also enables a user to share another computer CDROM, floppy drive or other resource, just as if the original computer had its own CDROM or other resource.
Explain client-server computing with examples.
As the term implies, client-server computing has two basic components, a client and a server. The client requests a service to be performed. This service might be to run an application, query a data base, print a document, or even perform a backup or recovery procedure. The server is the resource that handles the client's request. Clients are typically thought of as personal computers but a client can be a midrange system or even a mainframe. Servers are typically thought of as a midrange or mainframe systems, however a server can be another personal computer on the network. Client-server networks are like our restaurant example where specific computers provide one or more services to other computers within a network. Today's networks have computers for file serving, data base serving, application serving, and communications serving. Each of these servers is dedicated devices which provide a specific service to all authorized users within a network. Another example of client-server computing is the computer transactions using the client-server model.  For example, to check your bank account from your computer, a client program in your computer forwards your request to a server program at the bank. That program may in turn forward the request to its own client program that sends a request to a database server at another bank computer to retrieve your account balance. The balance is returned back to the bank data client, which in turn serves it back to the client in your personal computer, which displays the information for you.
Client-server computing provides the seamless integration of personal computers with host systems. This style of computing allows organizations to be responsive to their customers while still maintaining the security and integrity to manage their business effectively. Client-server computing generally refers to a computing model where two or more computers interact in such a way that one provides services to the other. This model allows customers to access information resources and services located anywhere within the customers information network. Customers are very interested in client/server computing because it allows them to be more responsive, as well as to effectively utilize all computing resources within their network. Another example of client-server is a data base server that uses the PC for the display (user interface) and processing (application logic) portions of an application, while the server provides data management portion of the application. On the other hand, an application server uses the PC for the display portion of an application, while using the server for both the processing and data management portions. In conclusion, the client-server network arrangement, network services are located in a dedicated computer whose only function is to respond to the requests of client. The server contain the file, print, application, security and other services in a central computer that is continuously available to respond to client request

Define and explain the functions of the following devices.
HUB - A device that connects the cables from computers and other devices such as printers in an Ethernet local area network. Traditionally, hubs are used for star topology networks, but they are often used with other configurations to make it easy to add and remove computers without bringing down the network. Smart hubs or switching hubs are often used to improve performance by managing traffic. It is also a connection device for networks, which allow multiple segments or computers to connect and share packets of information. Generally when we build a network using two or more computers, we need a hub. However, it is possible to connect two computers to each other directly without the need of hub but when we add a third computer in the network, we need a hub to allow a proper data communication within the network. There are many types of hubs with various features and specifications, which provide the type of functionality you need in building network. There are three main types of hubs namely Passive hub, Active hub and intelligent hub.
SWITCH: A network switch is a small hardware device that joins multiple computers together within one local area network (LAN) Technically, network switches operate at layer two (Data Link Layer) of the OSI model. Network switches appear nearly identical to network hubs, but a switch generally contains more intelligence (and a slightly higher price tag) than a hub. Unlike hubs, network switches are capable of inspecting data packets as they are received, determining the source and destination device of each packet, and forwarding them appropriately. By delivering messages only to the connected device intended, a network switch conserves network bandwidth and offers generally better performance than a hub. Different models of network switches support differing numbers of connected devices. Most consumer-grade network switches provide either four or eight connections for Ethernet devices. In a telecommunications network, a switch is a device that channels incoming data from any of multiple input ports to the specific output port that will take the data toward its intended destination. In the traditional circuit-switched telephone network, one or more switches are used to set up a dedicated though temporary connection or circuit for an exchange between two or more parties. On an Ethernet local area network (LAN), a switch determines from the physical device (Media Access Control or MAC) address in each incoming message frame which output port to forward it to and out of. In a wide area packet-switched network such as the Internet, a switch determines from the IP address in each packet which output port to use for the next part of its trip to the intended destination.  In the Open Systems Interconnection (OSI) communications model, a switch performs the layer 2 or Data-Link layer function. That is, it simply looks at each packet or data unit and determines from a physical address (the "MAC address") which device a data unit is intended for and switches it out toward that device. However, in wide area networks such as the Internet, the destination address requires a look-up in a routing table by a device known as a router. Some newer switches also perform routing functions (layer 3 or the Network layer functions in OSI) and are sometimes called IP switches.
On larger networks, the trip from one switch point to another in the network is called a hop. The time a switch takes to figure out where to forward a data unit is called its latency. The price paid for having the flexibility that switches provide in a network is this latency. Switches are found at the backbone and gateway levels of a network where one network connects with another and at the sub network level where data is being forwarded close to its destination or origin. The former are often known as core switches and the latter as desktop switches.  In the simplest networks, a switch is not required for messages that are sent and received within the network. For example, a local area network may be organized in a Token Ring or bus arrangement in which each possible destination inspects each message and reads any message with its address.
REPEATERS: repeater is an electronic device that receives a signal and retransmits it at a higher level and/or higher power, or onto the other side of an obstruction, so that the signal can cover longer distances. Repeaters are used in transmission systems to regenerate analog or digital signals distorted by transmission loss. Analog repeaters frequently can only amplify the signal while digital repeaters can reconstruct a signal to near its original quality. In a data network, a repeater can relay messages between sub networks that use different protocols or cable types. Hubs can operate as repeaters by relaying messages to all connected computers. A repeater cannot do the intelligent routing performed by bridges and routers.  Repeaters are often used in trans-continental and submarine communications cables, because the attenuation (signal loss) over such distances would be unacceptable without them. Repeaters are used in radio communication services. Radio repeaters often transmit and receive on different frequencies. A special subgroup of those repeaters is those used in amateur radio in both copper-wire cables carrying electrical signals, and in fiber optics carrying light. Repeaters are also used extensively in broadcasting, where they are known as translators, boosters or TV relay transmission. The purpose of a repeater is to extend the LAN segment beyond its physical limits (e.g. Ethernet is 500m for 10Base5). It is also a simple hardware device that moves all packets from one local area network segment to another. The main purpose of a repeater is to extend the length of the network transmission medium beyond the normal maximum cable lengths. Typically, repeaters are used to connect two physically close buildings together (when they are too far apart to just extend the segment). They can be used to connect floors of a building that would normally surpass the maximum allowable segment length.
Repeaters operate at the physical layer, i.e. the bottom layer of the seven-layer OSI reference model. They can only operate on the same type of physical layer, i.e., Ethernet-to-Ethernet, or token ring-to-token ring. They can connect 10Base5 to 10BaseT because they both use the same 802.3 MAC layer. Because repeaters provide no isolation between segments, and the repeater is transparent to both sides of the segment, both sides of the repeater appear as one long network segment
ROUTERS: A router is an electronic device that forwards data packets along networks. A router is connected to at least two networks, commonly two LANs or WANs or a LAN and its ISP’s network. Routers are located at gateways, the places where two or more networks connect. Routers use headers and forwarding tables to determine the best path for forwarding the packets, and they use protocols such as ICMP to communicate with each other and configure the best route between any two hosts. Very little filtering of data is done through routers. For most home users, they may want to set-up a LAN (Local Area Network) or WLAN (Wireless LAN) and connect all computers to the Internet without having to pay a full broadband subscription service to their ISP for each computer on the network. In many instances, an ISP will allow you to use a router and connect multiple computers to a single Internet connection and pay a nominal fee for each additional computer sharing the connection. This is when you will want to look at smaller routers, often called broadband routers that enable two or more computers to share an Internet connection.

Common network topologies being deployed in an organization.

Topology refers to the shape of a network, or the network's layout. How different nodes in a network are connected to each other and how they communicate are determined by the network's topology. Topologies are either physical or logical.  Below are the most common network topologies.

Mesh Topology
Devices are connected with many redundant interconnections between network nodes. In a true mesh topology every node has a connection to every other node in the network.

Bus Topology
All devices are connected to a central cable, called the bus or backbone.

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. Nodes communicate across the network by passing data through the hub.

Tree Topology
A hybrid topology. Groups of star-configured networks are connected to a linear bus backbone.

Different types of cabling used in LANs and their application. What is NIC and its components?
Cables types are:
1) Coaxial cables
2) Fiber optical cable
3) Twisted Pair

Twisted Pair is divided into two types namely Unshielded ( UTP )and Shielded (STP ) UTP is further Divided into three types namely Straight cable- used to connect similar devices like PC to switch, Cross Cable- used to connect similar devices like PC to PC, Switch to switch and Roll Over Cable - used to access the operating system of router's or switch on our system.
Coaxial cable is an electrical cable with an inner conductor surrounded by a tubular insulating layer typically of a flexible material with a high dielectric constant, all of which are surrounded by a conductive layer (typically of fine woven wire for flexibility, or of a thin metallic foil), and finally covered with a thin insulating layer on the outside. The term coaxial comes from the inner conductor and the outer shield sharing the same geometric axis. Coaxial cable is used as a transmission line for radio frequency signals, in applications such as connecting radio transmitters and receivers with their antennas, computer network (Internet) connections, and distributing cable television signals. One advantage of coax over other types of transmission line is that in an ideal coaxial cable the electromagnetic field carrying the signal exists only in the space between the inner and outer conductors. This allows coaxial cable runs to be installed next to metal objects such as gutters without the power losses that occur in other transmission lines, and provides protection of the signal from external electromagnetic interference. Coaxial cable should not be confused with other shielded cable used for carrying lower frequency signals such as audio signals. Shielded cable is similar in that it consists of a central wire or wires surrounded by a tubular shield conductor, but it is not constructed with the precise conductor spacing needed to function efficiently as a radio frequency transmission line.
Optical fiber is a glass or plastic fiber that carries light along its length. Fiber optics is the overlap of applied science and engineering concerned with the design and application of optical fibers. Optical fibers are widely used in fiber-optic communications, which permits transmission over longer distances and at higher bandwidths (data rates) than other forms of communications. Fibers are used instead of metal wires because signals travel along them with less loss, and they are also immune to electromagnetic interference.  Fibers are also used for illumination, and are wrapped in bundles so they can be used to carry images, thus allowing viewing in tight spaces. Specially designed fibers are used for a variety of other applications, including sensors and fiber lasers. Light is kept in the core of the optical fiber by total internal reflection. This causes the fiber to act as a waveguide. Fibers which support many propagation paths or transverse modes are called multi-mode fibers (MMF), while those which can only support a single mode are called single-mode fibers (SMF). Multi-mode fibers generally have a larger core diameter, and are used for short-distance communication links and for applications where high power must be transmitted. Single-mode fibers are used for most communication links longer than 550 meters (1,800 ft). Joining lengths of optical fiber is more complex than joining electrical wire or cable. The ends of the fibers must be carefully cleaved, and then spliced together either mechanically or by fusing them together with an electric arc.
Twisted pair is the ordinary copper wire that connects home and many business computers to the telephone company. To reduce crosstalk or electromagnetic induction between pairs of wires, two insulated copper wires are twisted around each other. Each connection on twisted pair requires both wires. Since some telephone sets or desktop locations require multiple connections, twisted pair is sometimes installed in two or more pairs, all within a single cable. For some business locations, twisted pair is enclosed in a shield that functions as a ground. This is known as shielded twisted pair (STP). Ordinary wire to the home is unshielded twisted pair (UTP). Twisted pair is now frequently installed with two pairs to the home, with the extra pair making it possible for you to add another line (perhaps for modem use) when you need it. Twisted pair comes with each pair uniquely color coded when it is packaged in multiple pairs. Different uses such as analog, digital, and Ethernet require different pair multiples. Although twisted pair is often associated with home use, a higher grade of twisted pair is often used for horizontal wiring in LAN installations because it is less expensive than coaxial cable. The wire you buy at a local hardware store for extensions from your phone or computer modem to a wall jack is not twisted pair. It is a side-by-side wire known as silver satin. The wall jack can have as many five kinds of hole arrangements or pin outs, depending on the kinds of wire the installation expects will be plugged in (for example, digital, analog, or LAN) . That's why you may sometimes find when you carry your notebook computer to another location that the wall jack connections won't match your plug.

What is NIC and it’s Components?
Network interface card (NIC) card is a network interface, or is also known as an Ethernet Adapter that is inside the back panel of the computer and connects to the cable or DSL modem. Most computers sold in the last 5 years have them pre-installed. A network interface card is used to connect a computer to an Ethernet network. This may be either using an external transceiver or through an internal integrated transceiver mounted on the network interface card PCB. The card usually also contains the protocol control firmware and Ethernet Controller needed to support the Medium Access Control (MAC) data link protocol used by Ethernet. Each network interface card is assigned an Ethernet source address by the manufacturer of the network interface card. This is normally stored in a PROM on the network interface card. The addresses are globally unique, and are assigned in blocks of 16 (or 8) million addresses to the Ethernet interface manufacturers, according to a flat addressing structure. This ensures that no two Ethernet network interface will ever have the same source address. Personal computers and workstations on a local area network (LAN) typically contain a network interface card specifically designed for the LAN transmission technology, such as Ethernet or Token Ring. Network interface cards provide a dedicated, full-time connection to a network. Most home and portable computers connect to the Internet through as-needed dial-up connection. The modem provides the connection interface to the Internet service provider. Some network interface card are installed right from the manufacturer while some are bought and fixed by computer engineers after the computer have been purchased.
1.            Double layer
2.            Radial aluminum electrolytic capacitors
3.            SMT aluminum electrolytic capacitors
4.            SMT ceramic capacitors
5.            Leaded ceramic capacitors
6.            Thick film chip resistors
7.            Current sensing resistors
8.            shielded power inductors
9.            un-shielded power inductors
10.         SMT film capacitors
11.         Leaded film capacitors
12.         Chips inductors
13.         EMI/ Noise products
14.         Leaded resistors
15.         physical media
16.         interconnecting devices
17.         networking software
18.         computers

Describe open system interconnection, description of each layer and its function
Open Systems Interconnection (OSI) is a standard description or reference model for how messages should be transmitted between any two points in a telecommunication network. Its purpose is to guide product implementers so that their products will consistently work with other products. The reference model defines seven layers of functions that take place at each end of a communication. Although OSI is not always strictly adhered to in terms of keeping related functions together in a well-defined layer, many if not most products involved in telecommunication make an attempt to describe them in relation to the OSI model. The main idea in OSI is that the process of communication between two end points in a telecommunication network can be divided into layers, with each layer adding its own set of special, related functions. Each communicating user or program is at a computer equipped with these seven layers of function. So, in a given message between users, there will be a flow of data through each layer at one end down through the layers in that computer and, at the other end, when the message arrives, another flow of data up through the layers in the receiving computer and ultimately to the end user or program. The actual programming and hardware that furnishes these seven layers of function is usually a combination of the computer operating system, applications such as our Web browser, TCP/IP or alternative transport and network protocols, and the software and hardware that enable you to put a signal on one of the lines attached to your computer.
OSI divides telecommunication into seven layers. The layers are in two groups. The upper four layers are used whenever a message passes from or to a user. The lower three layers up to the network layer are used when any message passes through the host computer. Messages intended for this computer pass to the upper layers. Messages destined for some other host are not passed up to the upper layers but are forwarded to another host. The seven layers in OSI are describe below.
Layer 7: The application layer: This is the layer at which communication partners are identified, quality of service is identified, user authentication and privacy are considered, and any constraints on data syntax are identified. This layer is not the application itself, although some applications may perform application layer functions.
Layer 6: The presentation layer: This is a layer, usually part of an operating system, that converts incoming and outgoing data from one presentation format to another for example, from a text stream into a popup window with the newly arrived text. Sometimes it is called the syntax layer.
Layer 5: The session layer: This layer sets up, coordinates, and terminates conversations, exchanges, and dialogs between the applications at each end. It deals with session and connection coordination.
Layer 4: The transport layer: This layer manages the end-to-end control for example, determining whether all packets have arrived and error-checking. It ensures complete data transfer.
Layer 3: The network layer: This layer handles the routing of the data (sending it in the right direction to the right destination on outgoing transmissions and receiving incoming transmissions at the packet level). The network layer does routing and forwarding.
Layer 2: The data-link layer: This layer provides synchronization for the physical level and does bit-stuffing for strings of 1's in excess of 5. It furnishes transmission protocol knowledge and management.
Layer 1: The physical layer: This layer conveys the bit stream through the network at the electrical and mechanical level. It provides the hardware means of sending and receiving data on a carrier.

PART E.   
User A Sending email Message to user B in a network. Explain the whole process in terms of data packets leaving the workstation of user A, travelling through all the layers of OSI model, until it reaches its destination and is open by user B.
A packet is a basic unit of communication over a digital network. A packet is also called a datagram, a segment, a block, a cell or a frame, depending on the protocol or network. When data has to be transmitted, it is broken down into similar structures of data, which are reassembled to the original data chunk once they reach their destination (From user A to B) When user A sends his email message, the network breaks the e-mail message into parts of a certain size in bytes. These are the packets. Each packet is then sent off to its destination (user B) by the best available route. A route might be taken by all the other packets in the message or by none of the other packets in the message. This makes the network more efficient. First, the network can balance the load across various pieces of equipment on a millisecond-by-millisecond basis. Second, if there is a problem with one piece of equipment in the network while a message is being transferred, packets can be routed around the problem, ensuring the delivery of the entire message.
In the same process, if there are other people sending a message on the network at the same time when user A is sending his email message going to user B, the whole messages will be in queue in the order they were sent and will be delivered to their various destinations. Each packet carries the information that will help it get to user B (destination) User A IP address, user B IP address, something that tells the network how many packets this e-mail message has been broken into and the number of this particular packet. The packets carry the data in the protocols that the Internet uses. i.e Transmission Control Protocol/Internet Protocol (TCP/IP). Each packet contains part of the body of user A message to user B. A typical packet contains perhaps 1,000 or 1,500 bytes. When a workstation wishes to send data, it uses the client network software to enclose the data in a packet' containing a header and a trailer. The header and trailer contain information for the destination computer. For example, the header contains the address of the destination computer. The exact form the packets take is determined by the protocol the network uses. When a data packet is put onto the network by a workstation, each computer on the network examines the packet to see who it is intended for. The packet quickly dissipates if it is not recognized, allowing other packets to be sent. 
With reference to the OSI model, packets travel from one layer to another as stated above. The transport layer manages the end-to-end control for example, determining whether all packets have arrived and error-checking. It ensures complete data transfer. The network layer handles the routing of the data (sending it in the right direction to the right destination on outgoing transmissions and receiving incoming transmissions at the packet level). The network layer does routing and forwarding. The physical layer also conveys the bit stream through the network at the electrical and mechanical level. It provides the hardware means of sending and receiving data on a carrier. The data link layer provides synchronization for the physical level. The presentation layer, usually part of an operating system, does the conversion of incoming and outgoing data from one presentation format to another for example, from a text stream into a popup window with the newly arrived text. Sometimes it is called the syntax layer. The application layer is where communication partners (different IP) are identified, quality of service is identified, and user authentication and privacy are considered. The session layer sets up, coordinates, and terminates conversations, exchanges, and dialogs between the applications at each end when user A message is finally received by user B (destination). It deals with session and connection coordination. The rate at which packets can be sent is called the bandwidth. This has a somewhat different meaning to how bandwidth is normally used.  As an example, a bandwidth of 10 Megabits per second means ten million individual 1s and 0s can pass through the network in one second.

·                     Data and computer communications (seventh edition by Williams Stallings)
·                     Class lecture note

1 comment: