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Unit 07 Computer Network Systems LO1 - Know types of network systems and protocols
Assessment Criteria P1 - Describe the types of networks available and how they relate to particular network standards and protocols M1 - Compare and contrast different network standards and protocols [IE3] P2 - Describe why different network standards and protocols are necessary P3 - Explain the key components required for client workstations to connect to a network and access network resources M2 - Compare the different options for the key components for an identified user’s needs [IE1, CT1] D1 - Develop proposals for networked solutions to meet an identified user’s need [IE6] P4 - Explain the function of interconnection devices P5 - Describe typical services provided by networks M3 - Describe where different network services would be used. P6 - Make a networked system secure. D2 - Evaluate the procedures organisations should take to secure their networks
AO1 - Assessment Criteria P1 - Describe the types of networks available and how they relate to particular network standards and protocols M1 compare the benefits and disadvantages of peer-to-peer network and client/server networks [IE3] P2 describe why different network standards and protocols are necessary The suggested scenario is that learners have been employed to explain possible network solutions to a business client • For P1, describing networks, protocols and standards, learners could produce a report/poster using diagrams. Alternatives are a small set of linked web pages or a presentation. • For P2, learners should be able to demonstrate they understand why different network standards and protocols are necessary. Examples given should be realistic. This can be linked to P1. • Before attempting M1, learners should, ideally, have the chance to see the operation of both types of networks and then the actual evidence presented as a verbal, written report etc would be based on real experience.
LO1 - Scenario You have been employed to explain possible network solutions to the management of a new primary school in the local area with a view to setting up, installing and protecting their networked machines and the information stored on these. The client at the end of the month wants a working network with expansion capabilities allowing up to 200 computers in different computer suites across the building to be connected, the addition of printers and shared resources, a central network pool for information and the capability of adding their media suite of Apples to this network on a restricted access basis. Currently they have two sites, the upper primary and lower primary that are not connected physically. They have100 workstations in the student areas across both sites, 50 base unit computers in the administration and staffing areas, 25 laptops in separate laptop cabinets and 25 Apple G4’s in the media suites. They have 20 shared printers across the two buildings, ten of which are accessible to students with network capabilities including one networkable colour printer in their library in the upper primary building. The school has been given several possible scenarios by their newly assigned network manager needs to know what would be best for the school, the future and how to protect this network from the outside and inside. Longer term they expect to have a working intranet accessible off site where files can be accessed on the network drives by students.
P1.1 - Types of Network There are three main types of networks that companies use: • local area network (LAN); • wide area network (WAN), internet; WAN technologies e.g. frame relay, MPLS, ATM; • Personal Area Network (PAN) Each of these Network systems has their own uses within a business environment and each have their own merits for the client/user. The choice of these is dependent on the size of the company, the need for security, the physical layout and proposed intent of the user. Even with forty years of network developments, the need for these layouts and protocols has not changed.
LAN – Local Area Network Networked computers linked by cables. DISTRIBUTED SYSTEMS Networks were developed allowing standalone computers to communicate with each other through cabling. LANs allow local network access allow global network access (such as to the Internet) by linking back to a network server. Processing is carried out both centrally on a ‘server’ and on the computers. These computers can either be base Units(machines with storage) or workstations (thin client). Different types of cabling allows communication between computers e.g. Star, linear, ring.
Local Area Network 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. 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 many LANs, cables are used to connect the network interface cards in each computer; other LANs may be wireless. All non wireless devices are connected along the cabling and information flows along that line through direct or an indirect path if the path is blocked or busy like water would flow through inter-connected pipes. Directing this traffic are hubs, routers and servers.
Wide Area Network Wide Area Networks (WANs) connect larger geographic areas, such as Florida, the United States, or the world. Dedicated transoceanic cabling or satellite uplinks may be used to connect this type of network. Using a WAN, schools in Florida can communicate with places like Tokyo in a matter of minutes, without paying enormous phone bills. These are usually dedicated or protected lines that separate the system from the Internet lines. A WAN is complicated. It uses multiplexers to connect local and metropolitan networks to global communications networks like the Internet. To users, however, a WAN will not appear to be much different than a LAN except for geographical location and speed of use.
P1.1 - Types of Network PAN Network - is a computer network organized around an individual person. Personal area networks typically involve a mobile computer, a cell phone and/or a handheld computing device such as a PDA. You can use these networks to transfer files including email and calendar appointments, digital photos and music. Personal area networks can be constructed with cables or wirelessly. USB and FireWire technologies often link together a wired PAN while wireless PANs typically use Bluetooth or sometimes infrared connections. Bluetooth PANs are also called piconets. Personal area networks generally cover a range of less than 10 meters (about 30 feet). Unlike with wireless LANs, only devices within this limited area typically participate in the network, and no online connection with external devices is defined. One device is selected to assume the role of the controller during wireless PAN initialization, and this controller device mediates communication within the WPAN. The controller broadcasts a beacon that lets all devices synchronize with each other and allocates time slots for the devices.
P1.1 – PAN Network Each device attempts to join the wireless PAN by requesting a time slot from the controller. The controller authenticates the devices and assigns time slots for each device to transmit data. The data may be sent to the entire wireless PAN using the wireless PAN destination address, or it may be directed to a particular device.
P1.1 - Types of Network P1.1 - Task 01 – Describe the technical purposes of Workstations, Base Units and associated peripherals. • P1.1 – Task 02 – Describe different common types of networks, and in technical detail describe how information is transferred around the system in terms of information flow. • For your client, they will need to connect all the machines in both buildings with a secure network layout with a system that links and shares files. They will need to share resources across these systems but have a separation between servers for different levels of students. • P1.1 – Task 03 – Suggest a Network system type and workstation purchase that will suit the needs of your client.
P1.2 – WAN information transference • Transferring information within a WAN network is done through systems of small bites send in sequence so the computer receiving the information can understand and have time to decipher the information as it is being sent. This is called Packet Switching. WAN particularly deals with these packets in a number of ways depending on how the network manager has constructed the network layers and protocols. One system is necessary, everything else will evolve around that packet switching method when that decision is made. Deciding in which type of WAN to construct can
P1.2 – WAN information transference MPLSis a type of switching, MPLS (multiprotocol label switching), was introduced by the IETF in 1999. As its name implies, MPLS enables multiple types of layer 3 protocols to travel over any one of several connection-oriented layer 2 protocols. IP addressing is the most commonly used layer 3 protocol, and so MPLS most often supports IP. MPLS can operate over Ethernet frames, but is more often used with other layer 2 protocols, like those designed for WANs. In fact, one of its benefits is the ability to use packet-switched technologies over traditionally circuit switched networks. MPLS can also create end-to-end paths that act like circuit-switched connections. ATM - (Asynchronous Transfer Mode) functions in the Data Link layer. Its ITU standard prescribes both network access and signal multiplexing techniques. Asynchronous refers to a communications method in which nodes do not have to conform to any predetermined schemes that specify the timing of data transmissions. In ATM communications, a node can transmit at any instant, and the destination node must accept the transmission as it comes. To ensure that the receiving node knows when it has received a complete frame, ATM provide start and stop bits for each character transmitted. When the receiving node recognizes a start bit, it begins to accept a new character. When it receives the stop bit for that character, it ceases to look for the end of that character’s transmission. ATM data transmission, therefore, occurs in random stops and starts.
P1.2 – WAN information transference • X.25is an analog, packet-switched technology designed for long-distance data transmission and standardized by the ITU. The original standard for X.25 specified a maximum of 64-Kbps throughput, but by 1992 the standard was updated to include maximum throughput of 2.048 Mbps. It was originally developed as a more reliable alternative to the voice telephone system for connecting mainframe computers and remote terminals. Later it was adopted as a method of connecting clients and servers over WANs. • Frame relay is an updated, a digital version of X.25 that also relies on packet switching. ITU and ANSI standardised frame relay in 1984. Frame relay protocols operate at the Data Link layer of the OSI model and can support multiple different Network and Transport layer protocols. The name is derived from the fact that data is separated into frames rather than packets, which are then relayed from one node to another without any verification or processing. • P1.1 – Task 04 – Describe with examples WAN information transfer technologies.
P1.2 – Network Topologies A topology is the shape or configuration of the networki.e. the way nodes are connected. The different types of topology depends on the geographic, physical and capable layouts of the space it is installed and each has their own benefits. Topologies are considered logical or physical topologies e.g. star, bus, ring, mesh, tree.
P1.2 – Star Topology A start topology is a network set out in the shape of a star, branching from one central fibre to the outliers. A star topology is designed with each node(file server, workstations, and peripherals) connected directly to a central network hub, switch, or concentrator. Data on a star network passes through the hub, switch, or concentrator before continuing to its destination. The hub, switch, or concentrator manages and controls all functions of the network. It also acts as a repeater for the data flow. This configuration is common with twisted pair cable; however, it can also be used with coaxial cableor fiber optic cable.
Star Topology • Advantages of a Star Topology • Easy to install and wire. • No disruptions to the network when connecting or removing devices. • Easy to detect faults and to remove parts. • Disadvantages of a Star Topology • Requires more cable length than a linear topology. • If the hub, switch, or concentrator fails, nodes attached are disabled. • More expensive than linear bus topologies because of the cost of the hubs, etc.
P1.2 – Bus Topology A linear bus topology consists of a main run of cable with a terminatorat each end. All nodes(file server, workstations, and peripherals) are connected to the linear cable. Using T junctions, more machines and peripherals can be added to the main line of cable. Information is sent down the cable to the router if the cable is long, or the server is the system is short where the information is dealt with. This relies heavily on the speed and function of the main trunk line. Similar to a real bus, information can step off along the line when it reaches its destination or can continue to the server (main depot) where it then gets sent back down the line to its destination like a print job coming out of a printer.
P1.2 – Bus Topology Advantages of a Linear Bus Topology • Easy to connect a computer or peripheral to a linear bus. • Requires less cable length than a star topology. Disadvantages of a Linear Bus Topology • Entire network shuts down if there is a break in the main cable. • Terminators are required at both ends of the backbone cable. • Difficult to identify the problem if the entire network shuts down. • Not meant to be used as a stand-alone solution in a large building.
P1.2 – Mesh Topology Mesh Network is a network where all the nodes are connected to each other and is a complete network. In a Mesh Network every node is connected to other nodes on the network through hops. Some are connected through single hops and some may be connected with more than one hope. While the data is travelling on the Mesh Network it is automatically configured to reach the destination by taking the shortest route which means the least number of hops. Data travels by hopping from one node to another and then reaches the destination node in a Mesh Topology Network. The advantage of a mesh topology is that if one cable breaks, the network can use an alternative route to deliver its packets. Mesh networks are not very practical in a LAN setting. For example, to network eight computers in a mesh topology, each computer would have to have seven network interface cards, and 28 cables would be required to connect each computer to the seven other computers in the network. Obviously, this scheme isn’t very scalable. However, mesh networks are common for metropolitan or wide area networks. These networks use devices called routers to route packets from network to network. For reliability and performance reasons, routers are usually arranged in a way that provides multiple paths between any two nodes on the network in a mesh-like arrangement.
P1.2 – Mesh Topology The Mesh Network is based on a very sensible concept and has lesser chances of a network breakdown. There are so many possible combinations of routes and hops a data transfer can take that it will reach the destination one way or the other. It is highly unlikely that all the nodes in a single Mesh Network will break down at any given point of time
P1.2 – 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. Tree topologies allow for the expansion of an existing network, and enable companies to configure a network to meet their needs. Tree networks are usually made out of necessity, more machines in one room, printers in another etc and a combination of different technologies usually exist until something better comes along.
P1.2 – Tree Topology • Advantages of a Tree Topology • Point-to-point wiring for individual segments. • Supported by several hardware and software companies. • Disadvantages of a Tree Topology • Overall length of each segment is limited by the type of cabling used. • If the backbone line breaks, the entire segment goes down. • More difficult to configure and wire than other topologies.
P1.2 – Ring Topology A Ring Topology network is a localised network joined by a central line that forms a loop. Information can find its way around the loop in either direction as long as there is an unbroken line. Computers can be joined to the loop through T junctions of drop cables as can additional devices. This makes everything localised and is usually formed on a single room or bank of computers. The smaller the ring, the quicker information can pass to the relevant point. This also allows computers to act as individual servers like an email server or print server.
P1.2 – Ring Topology Advantages of a Ring Network Information can flow both ways around the ring in order to reach its goal. One of the easier networks to set up and easy to add additional devices to. System is localised so there is less cabling. Disadvantages of a Ring Network Loop needs to be completed or terminated at one end. A break in the cable brings the whole thing down. File server needs to be localised or the ring joined to the trunk line. P1.2 – Task 05 – Define and describe how Network topologies work and how they transfer information from station to station. M1.2 – Task 06 – Suggest a Network Topology for your Client and Define and describe the benefits and disadvantages of using this topology in a school environment.
P1.3 – Network Access methods A protocol is a set of rules that enables effective communications to occur. We encounter protocols every day. For example, when you pay for groceries with a check, the clerk first tells you how much the groceries cost. You then write a check, providing information such as the date, the name of the grocery store, the amount written with numerals and spelled out, and your signature, and you give the check to the clerk. The clerk accepts the check and asks to see your driver’s license. You show the clerk your driver’s license, and the clerk looks at it, looks at you, looks at your driver’s license again, writes the driver’s license number on the check, asks whether you’ve gained some weight since the picture was taken, and then accepts the check. Here’s another example of an everyday protocol: making a phone call. You probably take most of the details of the phone calling protocol for granted, but it’s pretty complicated if you think about it: • When you pick up a phone, you have to listen for a dial tone before dialling the number. If you don’t hear a dial tone, you know that either (1) someone else in your family When you hear the dial tone, you initiate the call by dialling the number of the party you want to reach. If the person you want to call is in the same area code as you, most of the time you simply dial that person’s seven digit • phone number. If the person is in a different area code, you dial a one, the five-digit dialling code, and the person’s six-digit phone number. • If you hear a series of long ringing tones, you wait until the other person answers the phone. If the phone rings a certain number of times with no answer, you hang up and try again later. If you hear a voice say, “Hello,” you can begin a conversation with the other party. If the person on the other end of the phone has never heard of you, you say, “Sorry, wrong number,” hang up, and try again. • If you hear a voice that rambles on about how they’re not home but they want to return your call, you wait for a beep and leave a message. Etc. Etc. In computer terms network access and protocols work along the same line.
P1.3 – Network Access methods - CSMA The OSI model breaks the various aspects of a computer network into seven distinct layers. These layers are kind of like the layers of an onion: Each successive layer envelops the layer beneath it, hiding its details from the levels above. The OSI model is also like an onion in that if you start to peel it apart to have a look inside, you’re bound to shed a few tears. The OSI model is not a networking standard in the same sense that Ethernet and Token Ring are networking standards. Rather, the OSI model is a framework into which the various networking standards can fit. The OSI model specifies what aspects of a network’s operation can be addressed by various network standards. So, in a sense, the OSI model is sort of a standard of standards. The first three layers are sometimes called the lower layers. They deal with the mechanics of how information is sent from one computer to another over a network. Layers 4 through 7 are sometimes called the upper layers. They deal with how applications programs relate to the network through application programming interfaces.
P1.3 – Network Access methods - CSMA The Seven layers • The bottom layer of the OSI model is the Physical layer andaddresses the physical characteristics of the network, such as the types of cables used to connect devices, the types of connectors used, how long the cables can be, etc. For example, the Ethernet standard for 10BaseT cable specifies the electrical characteristics of the twisted-pair cables, the size and shape of the connectors, the maximum length of the cables, and so on. The star, bus, ring, and mesh network topologies in Task P1.1 apply to the Physical layer. • The Data Link layer is the lowest layer at which meaning is assigned to the bits that are transmitted over the network. Data link protocols address things such as the size of each packet of data to be sent, a means of addressing each packet so that it’s delivered to the intended recipient, and a way to ensure that two or more nodes don’t try to transmit data on the network at the same time. The Data Link layer also provides basic error detection and correction. • The Network layer handles the task of routing network messages from one computer to another. The two most popular layer 3 protocols are IP (which is usually paired with TCP) and IPX (normally paired with SPX for use with Novell and Windows networks). • The Transport layer is the layer where you’ll find two of the most well-known networking protocols: TCP (normally paired with IP) and SPX (normally paired with IPX). As its name implies, the Transport layer is concerned with the transportation of information from one computer to another. The main purpose of the Transport layer is to ensure that packets are transported reliably and without errors. The Transport layer does this task by establishing connections between network devices, acknowledging the receipt of packets, and resending packets that are not received or are corrupted when they arrive.
P1.3 – Network Access methods - CSMA The Seven layers • The Session layerestablishes conversations known as sessions between networked devices. Each of these transmissions is handled by the Transport layer protocol. The session itself is managed by the Session layer protocol. A single session can include many exchanges of data between the two computers involved in the session. After a session between two computers has been established, it is maintained until the computers agree to terminate the session. • The Presentation layeris responsible for how data is represented to applications. Most computers including Windows, UNIX, and Macintosh computers use the American Standard Code for Information Interchange (ASCII) to represent data. However, some computers (such as IBM mainframes) use a different code, which is not compatible with each other. To exchange information between a mainframe computer and a Windows computer, the Presentation layer must convert the data from ASCII to the other language and vice versa. The Presentation layer can also apply compression techniques so that fewer bytes of data are required to represent the information when it’s sent over the network. At the other end of the transmission, the Presentation layer then uncompresses this data. • The Application layer, deals with the techniques that application programs use to communicate with the network. Application programs such as Microsoft Office aren’t a part of the Application layer. Rather, the Application layer represents the programming interfaces that application programs such as Microsoft Office or Adobe products use to request network services. Some of the better-known Application layer protocols are DNS (Domain Name System) for resolving Internet domain names. FTP (File Transfer Protocol) for file transfers. SMTP (Simple Mail Transfer Protocol) for e-mail etc.
P1.3 – Network Access methods – Token Passing Token passing In CSMA/CD and CSMA/CA the chances of collisions are there. As the number of hosts in the network increases, the chances of collisions also will become more. In token passing, when a host want to transmit data, it should hold the token, which is an empty packet. The token is circling the network in a very high speed. If any workstation wants to send data, it should wait for the token. When the token has reached the workstation, the workstation can take the token from the network, fill it with data, mark the token as being used and place the token back to the network. This benefits a network because it means information is shared and queued, when one machine is ready and ahs been waiting it will get the basket and pass on the information in a first come, first serve basis. This can be seen like a printer waiting t print you network job when others are ahead of you. Your network takes the next token and when it is your turn it then gets its place in the queue while you get on with the other jobs that need doing. P1.3 – Task 07 – Describe the system of CSMA and Token Passing M1.3 – Task 08 – Explain Token Passing and CSMA in terms of how this system would benefit students within a school environment.
P1.4 – Network Access models – TCP/IP • The TCP/IP family uses four layers while ISO OSI uses seven layers as shown in the figure above. The TCP/IP and ISO OSI systems differ from each other significantly, although they are very similar on the network and transport layers. • Except for some exceptions like SLIP or PPP, the TCP/IP family does not deal with the link and physical layers. Therefore, even on the Internet, we use the link and physical protocols of the ISO OSI model. • TCP/IP (Transmission Control Protocol/Internet Protocol) is the basic communication language or protocol of the Internet. It can also be used as a communications protocol in a private network (either an intranet or an extranet). When you are set up with direct access to the Internet, your computer is provided with a copy of the TCP/IP program just as every other computer that you may send messages to or get information from also has a copy of TCP/IP.
P1.4 – Network Access models – TCP/IP • TCP/IP is a two-layer program. The higher layer, Transmission Control Protocol, manages the assembling of a message or file into smaller packets that are transmitted over the Internet and received by a TCP layer that reassembles the packets into the original message. The lower layer, Internet Protocol, handles the addresspart of each packet so that it gets to the right destination. Each gatewaycomputer on the network checks this address to see where to forward the message. Even though some packets from the same message are routed differently than others, they'll be reassembled at the destination. • TCP/IP uses the client/server model of communication in which a computer user (a client) requests and is provided a service (such as sending a Web page) by another computer (a server) in the network. TCP/IP communication is primarily point-to-point, meaning each communication is from one point (or hostcomputer) in the network to another point or host computer. TCP/IP and the higher-level applications that use it are collectively said to be "stateless" because each client request is considered a new request unrelated to any previous one (unlike ordinary phone conversations that require a dedicated connection for the call duration). Being stateless frees network paths so that everyone can use them continuously. (Note that the TCP layer itself is not stateless as far as any one message is concerned. Its connection remains in place until all packets in a message have been received.)
P1.4 – Network Access methods - Peer to Peer A workgroup or peer-to-peer network is one in which all computers on the network can pool their resources together. Each individual computer usually retains its control over files, folders, and applications; however, every computer on the network can use another’s printer, scanner, CD drive, and so on. Workgroup networks contain a small number of computers. Workgroups can be made up of 2, 5, or even 10 computers. It is important to note that the more computers in the workgroup, the slower the network may run. A workgroup network is easy to maintain and set up. It’s also cost effective, especially for home network use. A wide range of cabling and networking solutions are available for your home network. Some solutions provide fast and powerful networking; others offer slower connections yet reliable service. You might want to use a workgroup network in your small business. It can be efficient if you keep the network small—ten or fewer computers. In an office situation, people will access the computers and the network more than in a home situation; therefore, network traffic is likely to be higher than in the home as well. Consider building a workgroup network with an eye toward upgrading to a client/server network in the near future, especially if you’ll be adding more computers to the network.
P1.4 – Network Access methods - Peer to Peer Drawbacks of peer-to-peer networks Because peer-to-peer networks are Windows-based, they’re subject to the inherent limitations of Windows. Windows is designed primarily to be an operating system for a single-user, desktop computer rather than function as part of a network, so Windows can’t manage a file or printer server as efficiently as a real network operating system. If you don’t set up a dedicated network server, someone may have to live with the inconvenience of sharing his or her computer with the network.. The cost difference between peer-to-peer networks and NetWare or Windows Server is less significant in larger networks (say, ten or more clients). Peer-to-peer networks don’t work well when your network starts to grow. Peer-to-peer servers just don’t have the security or performance features required for a growing network. Advantages of peer-to-peer networks • The main advantage of a peer-to-peer network is that it is easier to set up and use than a network with a dedicated server. Peer-to-peer networks rely on the limited network server features that are built into Windows, such as the ability to share files and printers. Networking Wizard that automatically configures a basic network for you so you don’t have to manually configure any network settings. • They can be less expensive than server-based networks. Here are some of the reasons that peer-to-peer networks are inexpensive: • Peer-to-peer networks don’t require you to use a dedicated server computer. Any computer on the network can function as both a network server and a user’s workstation. (However, you can configure a computer as a dedicated server if you want to. Doing so results in better performance but negates the cost benefit of not having a dedicated server computer.) • Peer-to-peer networks are easier to set up and use, which means that you can spend less time figuring out how to make the network work and keep it working. • The operating system itself, either NetWare and Windows Server can cost as much as £160 per user. And the total cost increases as your network grows, although the cost per user drops. P1.4– Task 09 – Define a TCP and Peer to Peer models and the hardware necessary to provide external access. M1.4 – Task 10 – Define the advantages and disadvantages of operating a TCP or Peer to peer network within a school environment.
P1.5 – Client Server network Server computers are the lifeblood of any network. Servers provide the shared resources that network users crave, such as file storage, databases, e-mail, Web services, and so on. Choosing the equipment you use for your network’s servers is one of the key decisions you’ll make when you set up a network. In this section, I describe some of the various ways you can equip your network’s servers. The simple logic is: Only the smallest networks can do without at least one dedicated server computer. For a home network or a small office network with only a few computers, you can get away with true peer-to-peer networking. That’s where each client computer shares its resources such as file storage or printers, and a dedicated server computer is not needed. In some networks, a server computer is a server computer and nothing else. This server computer is dedicated solely to the task of providing shared resources, such as hard drives and printers, to be accessed by the network client computers. Such a server is referred to as a dedicated server because it can perform no other task besides network services. A network that relies on dedicated servers is sometimes called a client/server network. Dedicated servers can have more than one function but as networks expand servers tend to have a single use, file server, Intranet, Mail server, Http server, admin server, student server, backup server etc.
M1.5 – Client Server network - Advantages • Scalability: Scalability refers to the ability to increase the size and capacity of the server computer without unreasonable hassle. It is a major mistake to purchase a server computer that just meets your current needs because, you can rest assured, your needs will double within a year. If at all possible, equip your servers with far more disk space, RAM, and processor power than you currently need. • Reliability: The old adage “you get what you pay for” applies especially well to server computers. Why spend $3,000 on a server computer when you can buy one with similar specifications at a discount electronics store for $1,000? One reason is reliability. When a client computer fails, only the person who uses that computer is affected. When a server fails, however, everyone on the network is affected. The less expensive computer is probably made of inferior components that are more likely to fail. • Availability: This concept of availability is closely related to reliability. When a server computer fails, how long does it take to correct the problem and get the server up and running again? Server computers are designed so that their components can be easily diagnosed and replaced, thus minimizing the downtime that results when a component fails. In some servers, components are hot swappable, which means that certain components can be replaced without shutting down the server. Some servers are designed to be fault-tolerant so that they can continue to operate even if a major component fails. • Service and support: Service and support are factors often overlooked when picking computers. If a component in a server computer fails, do you have someone on site qualified to repair the broken computer? If not, you should get an on-site maintenance contract for the computer. Don’t settle for a maintenance contract that requires you to take the computer in to a repair shop or, worse, mail it to a repair facility. You can’t afford to be without your server that long.
M1.5 – Client Server network - Disadvantages • A large disadvantage to being a member of a network is system security. You don’t want a child to accidentally delete or modify data in an accounting file, for example. • When you’re sharing your equipment (such as a printer or Zip drive) over a network, you take the chance that the equipment won’t be readily available when you need it. Say a student just sent a 24-page color document to a networked inkjet printer. You’ll have to wait your turn to print, and that could take awhile, depending on the network setup, printer speed, and so on. • Additionally, sharing files and applications can cause problems if two people want to use a file at the same time. Some applications are built for more than one user to use program files at the same time; others are not. • Security of your files can be a slight problem on a workgroup network. You do, however, have the option of not sharing all your files and folders. You can choose only those folders to which you want to grant access and share them. Security issues are more serious in a business environment than in your home network. Sensitive files and data (salaries, for example) must be private from the general population. • Another disadvantage is backing up the computer. With workgroup networking, each computer user is responsible for his or her own backups. Perhaps not every user will need a backup of the data on his or her computer; however, each user should understand the importance of backups and understand how. • And expense, a network server can cost several hundred, additional hard drives, backup software and hardware and a lot of extra cabling all cost. P1.5 – Task 11– Define a Client Server network and the technical hardware necessary to provide internal and external access. M1.5 – Task 12 – Define the advantages and disadvantages of operating a Client Server network within a school environment.
P1.6 – Network Layer Protocols Bluetooth - Bluetooth is the name of a short-range wireless network technology that’s designed to let devices connect to each other without need for cables or a Wi-Fi network access point. The two main uses for Bluetooth are to connect peripheral devices such as keyboards or mice to a computer and to connect hand-held devices such as phones and PDAs to computers. Bluetooth is slow — about 721Kbps, way slower than Wi-Fi networks. Bluetooth isn’t designed to transport large amounts of data, such as huge video files. For that, you should use Wi-Fi. 3g and 4G - Based on the ITU standards, the 3G and 4G network is the current generations of mobile networking and telecommunications. It features a wider range of services and advances network capacity over the previous 2G network. The 3G network also increases the rate of information transfer known as spectral efficiency. A 3G network provides for download speeds of 14.4 megabits per second and upload speeds of 5.8 megabits per second. The minimum speed for a stationary user is 2 megabits per second. A user in a moving vehicle can expect 348 kilobits per second. This scheme is known as a layered system. Each transmission features three layers of information. The top layer is general service. The middle layer is a control data transmission. The bottom layer is the basic connectivity information. There is a distinct difference from Wi-Fi, or IEEE 802.11 technology, and this network. Wi-Fi is basically a short range network that offers high- bandwidth designed for data transfer. 3G networks are geared towards cellular telephone technology and Internet access.
P1.6 – Network Layer Protocols Wi-Fi - The common name for wireless networking using the 802.11 protocols. With wireless networking, you don’t need cables to connect your computers. Instead, wireless networks use radio waves to send and receive network signals. As a result, a computer can connect to a wireless network at any location in your home or office. Wireless networks are especially useful for notebook computers. After all, the main benefit of a notebook computer is that you can carry it around with you wherever you go. • A wireless network is often referred to as a WLAN, for wireless local area network. The term Wi-Fi is often used to describe wireless networks, although it technically refers to just one form of wireless networks: the 802.11b standard. • A wireless network has a name, known as a SSID. SSID stands for service set identifier . Each of the computers that belong to a single wireless network must have the same SSID. • Wireless networks can transmit over any of several channels. In order for computers to talk to each other, they must be configured to transmit on the same channel. • The simplest type of wireless network consists of two or more computers with wireless network adapters. This type of network is called an ad-hoc mode network. • A more complex type of network is an infrastructure mode network. All this really means is that a group of wireless computers can be connected not only to each other, but also to an existing cabled network via a device called a wireless access point, or WAP. P1.6 – Task 13 – Discuss the technologies behind Wi-Fi, Bluetooth, 3Gand 4G M1.6 – Task 14 - Outline the factors affecting range and speed of wireless technologies within a school environment.
P1.7 – Network Layer Protocols AppleTalk - Apple computers have their own suite of network protocols known as AppleTalk because of the language barrier between operating systems and hardware differences. The AppleTalk suite includes a Physical and Data Link layer protocol called LocalTalk, but can also work with standard lower level protocols, including Ethernet and Token Ring. Transmission Control Protocol (TCP): Provides reliable connection oriented transmission between two hosts. TCP establishes a session between hosts, and then ensures delivery of packets between the hosts. Internet Protocol (IP): A routable protocol that uses IP addresses to deliver packets to network devices. IP is an intentionally unreliable protocol, so it doesn’t guarantee delivery of information. It works on the Network layer of the TCP and communicates with these devices to provide a function, printing, internet access, file access, communication. It does not operate applications but initiates communication.
P1.7 – Network Layer Protocols Several LAN systems have been created independently from each other. Ethernet II is still used. Some years ago, the Institute of Electrical and Electronics Engineers (IEEE) came up with a project. The aim of this project was to unify existing initiatives and work out standards for particular LAN types (e.g. Ethernet, Arcnet, Token Ring, etc). These standards described the Media Access Control (MAC) layer for each type. The IEEE 802.3 standard was created for Ethernet, IEEE 802.4 for Token Bus, IEEE 802.5 for Token Ring, and so on. 802.2 - A joint standard, IEEE 802.2, was created for the Logical Link Control (LLC) layer of all systems. In other words, the LAN link layer has been divided into two sub-layers. The bottom MAC layer—partially overlapping the physical layer—deals with access to the communication medium. The top LLC layer enables you to initiate, administer, and terminate logical connections between individual LAN stations.
P1.7 – Network Layer Protocols 802.3 or Ethernet - Ethernet has been around in various forms since the early 1970s. The current incarnation of Ethernet is defined by the IEEE standard known as 802.3. Various types of Ethernet operate at different speeds and use different types of media. However, all the versions of Ethernet are compatible with each other, so you can mix and match them on the same network by using devices such as bridges, hubs, and switches to link network segments that use different types of media. This is pretty much the standard used in computers, speeds vary but the technology stays the same. 802.5 – Put simply this is the network card that pushes the technology behind Token Rings. This card addressing managed the tokens, sends the information around the network looking for the outlet for the information and gathering in the tokens sent out by users. When it receives the token and deals with it, the information is changed on the users machine to indicate that the token has been received and dealt with. The card then discards additional requests from the network to process the information again unless the user requests that the information is different or has changed.
P1.7 – Network Layer Protocols The User Datagram Protocol (or UDP) is a connectionless Transport layer protocol that is used when the overhead of a connection is not required. After UDP has placed a packet on the network (via the IP protocol), it forgets about it. UDP doesn’t guarantee that the packet actually arrives at its destination. Most applications that use UDP simply wait for any replies expected as a result of packets sent via UDP. If a reply doesn’t arrive within a certain period of time, the application either sends the packet again or gives up. Probably the best-known Application layer protocol that uses UDP is DNS, the Domain Name System. When an application needs to access a domain name such as www.brookeweston.org, DNS sends a UDP packet to a DNS server to look up the domain. When the server finds the domain, it returns the domain’s IP address in another UDP packet. (Actually, the process is much more complicated than that. FDDI - Fibre Distributed Data Interface, a 100Mbps network standard used with fibre-optic backbone. When FDDI is used, FDDI/Ethernet bridges connect Ethernet segments to the backbone. Fibre optic cabling and fibre optic data management is expensive but it manages large networks and traffic at a far faster speed. The FDDI cards manage the information transfer rate along those lines, sending on further information when the router or server receives the first sections. P1.7 – Task 15 – Discuss the technologies behind Network Protocols. M1.5 – Task 16 - Discuss the advantages and Disadvantages of each Protocol in a School Environment.
P1.8 – Application Layer Protocols DNS - To provide a unique DNS name for every host computer on the Internet, DNS uses a time-tested technique: divide and conquer. DNS uses a hierarchical naming system that’s similar to the way folders are organized hierarchically on a Windows computer. Instead of folders, however, DNS organizes its names into domains. Each domain includes all the names that appear directly beneath it in the DNShierarchy. For example, on the right shows a small portion of the DNS domain tree. At the very topof the tree is the root domain, which is the anchor point for all domains. Directly beneath the root domain are four top-level domains, named edu, com, org, and gov. A DNS server is a computer that runs DNS server software, helps to maintain the DNS database, and responds to DNS name resolution requests from other computers. Although many DNS server implementations are available, the two most popular are Bind and the Windows DNS service. Bind runs on UNIX-based computers (including Linux computers), while Windows DNS runs on Windows computers. Both provide essentially the same services and can interoperate with each other. The key to understanding how DNS servers work is to realize that the DNS database — that is, the list of all the domains, sub-domains, and host mappings — is a massively distributed database. No single DNS server contains the entire DNS database. Instead, authority over different parts of the database is delegated to different servers throughout the Internet.
P1.8 – Application Layer Protocols DHCP - Every host on a TCP/IP network must have a unique IP address. Each host must be properly configured so that it knows its IP address. When a new host comes online, it must be assigned an IP address that is within the correct range of addresses for the subnet and is not already in use. Although you can manually assign IP addresses to each computer on your network, that task quickly becomes overwhelming if the network has more than a few computers. That’s where DHCP, the Dynamic Host Configuration Protocol, comes into play. DHCP automatically configures the IP address for every host on a network, thus assuring that each host has a valid, unique IP address. DHCP even automatically reconfigures IP addresses as hosts come and go. The DHCP can save a network administrator many hours of tedious configuration work. Although the primary job of DHCP is to dole out IP addresses and subnet masks, DHCP actually provides more configuration information than just the IP address to its clients. The additional configuration information is referred to as DHCP options. The following is a list of some common DHCP options that can be configured by the server: • The router address, also known as the Default Gateway address • The expiration time for the configuration information • Domain name • DNS server address • WINS server address
P1.8 – Application Layer Protocols HTTP - The Hypertext Transfer Protocol serves for information searching on the Internet (or intranet). A client-server relationship is the basic architecture of communication in HTTP protocol. If a direct TCP connection between a client and a server is established, the user types the Uniform Resource Identifier (URI) he or she wants to survey into the browser: The client first takes the server name from the URI and with the help of DNS, translates it into the IP address (1 and 2). Then the client establishes a TCP connection with the obtained IP address of the server. The browser inputs the HTTP request into the newly created channel (3), and the server responses with an HTTP response (4) within the same TCP connection. Then, the browser displays the response to the user. It is important that the browser displays the web pages to the user. Every web page usually consists of many objects and every object must be downloaded by a separate HTTP request from the web server. Only the basic text of the web page is downloaded by the first request; the basic text usually contains many references for objects necessary for properly displaying the web page. Thus, in the next step, separate TCP connections with the web server are established simultaneously to download each individual object. This process creates transmission peaks in the transmission channel. A user usually sets the browser (client) so that the responses (web pages) will be displayed to the user and stored in a cache to reduce the response time and network bandwidth consumption on future equivalent requests. When repeating the request, the information can be displayed to the user from the local cache. As usual, caching has problems with fresh information. Various strategies are used to overcome the problem of when to display cached information and when the client should transfer information from the server . It is possible for a client to ask a server by HTTP: "Have you changed the web page?" Only if the reply is "Yes" will the page be transferred from the server. Some responses of the server can be marked not to be stored into the cache. The client must contact the target server even if it has a cached copy of the data being requested. This is called a HTTP server.
P1.8 – Application Layer Protocols FTP - File Transfer Protocol (FTP) is an application protocol suitable for file transfers in a computer network based on TCP/IP. FTP is used for file transfers in computer networks using TCP/IP protocol. A user works with a user interface that is represented either by the command line of the FTP program, a GUI FTP utility, or an Internet browser. In the Windows world, an FTP server is integrated with Microsoft’s Web server, Internet Information Services, or IIS. As a result, you can manage FTP from the IIS management console along with other IIS features. On UNIX and Linux systems, FTP isn’t usually integrated with a Web server. Instead, the FTP server is installed as a separate program. You’re usually given the option to install FTP when you install the operating system. When you run an FTP server, you expose a portion of your file system to the outside world. As a result, you need to be careful about how you set up your FTP server so that you don’t accidentally allow hackers access to the bowels of your file server. When you set up an FTP site, Internet Information Services creates an empty home directory for the site. Then it’s up to you to add to this directory whatever files you want to make available on the site. The easiest way to do that is to simply open a My Computer window and copy the files to the site’s home directory.
P1.8 – Application Layer Protocols SMTP - One of several key protocols that are used to provide e-mail services. The SMTP design is based on the following model of communication: as the result of a user mail request, the sender-SMTP establishes a two-way transmission channel to a receiver-SMTP. The receiver-SMTP may be either the ultimate destination or an intermediate. SMTP commands are generated by the sender-SMTP and sent to the receiver-SMTP. SMTP replies are sent from the receiver-SMTP to the sender-SMTP in response to the commands. Once the transmission channel is established, the SMTP-sender sends a MAIL command indicating the sender of the mail. If the SMTP-receiver can accept mail it responds with an OK reply. The SMTP-sender then sends a RCPT command identifying a recipient of the mail. If the SMTP-receiver can accept mail for that recipient it responds with an OK reply; if not, it responds with a reply rejecting that recipient (but not the whole mail transaction). The SMTP-sender and SMTP-receiver may negotiate several recipients. When the recipients have been negotiated the SMTP-sender sends the mail data, terminating with a special sequence. If the SMTP-receiver successfully processes the mail data it responds with an OK reply. The dialog is purposely lock-step, one-at-a-time. P1.8– Task 17 – Discuss the technologies behind HTTP, SMTP and FTP, their functions M1.8 – Task 18 - Outline the practical applications of using these technologies within a school environment.
Task List P1.1 - Task 01 – Describe the technical purposes of Workstations, Base Units and associated peripherals. P1.1 – Task 02 – Describe different common types of networks, and in technical detail describe how information is transferred around the system in terms of information flow. P1.1 – Task 03 – Suggest a Network system type and workstation purchase that will suit the needs of your client. P1.1 – Task 04 – Describe with examples WAN information transfer technologies. P1.2 – Task 05 – Define and describe how Network topologies work and how they transfer information from station to station. M1.2 – Task 06 – Suggest a Network Topology for your Client and Define and describe the benefits and disadvantages of using this topology in a school environment. P1.3 – Task 07 – Describe the system of CSMA and Token Passing M1.3 – Task 08 – Explain Token Passing and CSMA in terms of how this system would benefit students within a school environment. P1.4– Task 09 – Define TCP and Peer to Peer models and the hardware necessary to provide external access. M1.4 – Task 10 – Define the advantages and disadvantages of operating a TCP or Peer to peer network within a school environment. P1.5 – Task 11– Define a Client Server network and the technical hardware necessary to provide internal and external access. M1.5 – Task 12 – Define the advantages and disadvantages of operating a Client Server network within a school environment. P1.6 – Task 13 – Discuss the technologies behind Wi-Fi, Bluetooth, 3Gand 4G M1.6 – Task 14 - Outline the factors affecting range and speed of wireless technologies within a school environment. P1.7 – Task 15 – Discuss the technologies behind Network Protocols. M1.5 – Task 16 - Discuss the advantages and Disadvantages of each Protocol in a School Environment. P1.8– Task 17 – Discuss the technologies behind HTTP, SMTP and FTP, their functions M1.8 – Task 18 - Outline the practical applications of using these technologies within a school environment.