IBDP Computer Science: Computer Networks

Router

A device that transfers data from one network to another in an intelligent way. Its use is to join multiple network and serve as an intermediary between these networks so that data can be exchanged effectively and efficiently between network devices of those networks. Example..connecting home network to the internet.

Hub

A device that uses its ports to connect devices (computers, printers, etc.) together. Data arriving at a hub is copied and send to all the devices on the network.

Internet

A global network connecting millions of computers, making it possible to exchange information.

Personal Area Network (PAN)

A network of devices such as smartphones, notebooks, and tablets using Bluetooth technology

TCP/IP

Transmission Control Protocol/Internet Protocol. Protocol that connects computers to the Internet. Tells computers how to exchange information over the Internet.

Outline the characteristics of different transmission media

Transmission media may guided (wired) or unguided (wireless) Twisted Pair Least inexpensive and widely used Limited in terms of data rate and distance Coaxial Cable Can support higher frequencies and data rates Superior frequency characteristics compared to twisted pair Optical Fiber Much higher bandwidth Smaller size and light weight Greater repeater spacing Lower cost and fewer error sources

Demerits of TCP/IP

* In this, the transport layer does not guarantee delivery of packets. * The model cannot be used in any other application. * Replacing protocol is not easy. * It has not clearly separated its services, interfaces and protocols.

Merits of TCP/IP Model

* It operated independently. * It is scalable. * Client/server architecture. * Supports a number of routing protocols. * Can be used to establish a connection between two computers.

Wide Area Network

A computer network that covers a large geographical area. Most WANs are made up of several connected LANs. -Wide Area Network -Two or more LAN -Potential Large Geographic distance -Internet = WAN -Networks Use same protocols. Example: Klein ISD, one can access internet in any Klein school which spans across a large geographic distance.

Switch

A computer networking device that connects network segments. However, unlike a hub, the switch can identify which network device is connected to which port.

Client

A computer that requests data or services from a server.

Evaluate the use of a VPN.

A network protocol defines rules and conventions for communication between network devices. A protocol is, in one sense, nothing more than an agreement that a particular type of data will be formatted in a particular manner. HTTP, FTP, POP3, SMTP, IMAP, TCP are all examples of network protocols. OR Protocol: when data is exchanged through a network it must follow specific rules in order for the data to be compatible with all networks; sets of rules between network devices

Check digit

A one-digit character, alphabetic or numeric, used to verify the validity of a unique identifier. An extra digit added to numerical data that is used to check data integrity after input, transmission, storage and processing.

Virtual Private Network (VPN)

A private data network that creates secure connections, or "tunnels," over regular Internet lines

Extranet

A private network that uses Internet technologies to share business information with select corporate partners or key customers.

Protocol

A set of rules governing the exchange or transmission of data between devices. A protocol that is recognized as the standard for a specific type of transfer is called standard protocol. For example TCP/IP

Evaluate the effectiveness of encryption, authentication, and MAC address filtering as they relate to wireless networking.

AC Address filtering will discourage the casual user from accessing your network but it will do very little to deter knowledgeable hackers who can use software to scan for MAC Addresses of legitimate devices currently accessing your network and then spoof their own MAC into a validated one. The best way to secure a wireless network is combine both encryption and authentication technology using the WPA2 standard. However, for authentication to be effective a strong password must be used.

Outline the advantages and disadvantages of wireless networks.

Advantages 1. Convenience 2. Mobility 3. Productivity 4. Deployment 5. Expandability 6. Cost Disadvantages 1. Security 2. Range 3. Reliability 4. Speed

P2P

An abbreviation of peer-to-peer. Software (often free) which allows you to download files directly from a single computer anywhere in the world that also has the same software installed. Sometimes known as P2P, this is a commonly used way of accessing music, software and films.

Explain how data is transmitted by packet switching.

Below are the steps used to send packets over a network using packet switching: 1. The sending computer chops data into small packets, with an address on each one telling the network devices where to send them. 2. Each packet is assembled with a small piece of an e-mail, music file or whatever type of file is being transmitted inside the packet. 3. The sending computer sends the packet to a nearby router and forgets about it. The nearby router send the packet to another router that is closer to the recipient computer. That router sends the packet along to another, even closer router, and so on. 4. When the receiving computer finally gets the packets (which may have all taken completely different paths to get there), it uses instructions contained within the packets to reassemble the data into its original state. OR Data is grouped into bundles Router examines each bundle of data as it passes and makes a decision of exactly where it should go by knowing part of your computer's MAC Address. Routers understand the most common network protocols. They know the format of the addresses, how many bytes are in the basic package of data sent out over the network, and how to make sure all the packages reach their destination and get reassembled. Since packets can be sent along different pathways you don't have to build a dedicated network between you and someone else. Your information flows over any one of thousands of different routes to get from one computer to the other.

Network Cable

Cables that use either a BNC connector or an RJ-45 connector. These cables are used to transmit data between computers.

Modem

Communications hardware device that facilitates the transmission of data. It is also called modulator/demodulator and converts computer digital signals into analog and back.

Dead Lock

Computer networks are based on passing messages from computer to computer. The computers must have a protocol established that determines the order of communication. Without a proper protocol a situation called a deadlock can occur. A deadlock is a situation in which two or more communicating computers are each waiting for the other to send a message, and thus neither ever does. In a networking environment, deadlocks can occur due to lost or corrupt signals during communication. A protocol must be in place to handle these types of situations or the communicating will break down.

Gateway

Computer which acts as a bridge between a local area network and the Internet.

Local Area Network (LAN)

Connects a group of computers in close proximity, such as in an office building, school, or home. Communication between the nodes/computers may be through cables and/or Microwave transmission. - Few Computers -Close geographic area (Usually One room or building) Example: Houses and Small offices are LAN.

Explain why compression of data is often necessary when transmitting across a network.

Data compression- reducing the amount of space needed to store a piece of data Data in the past was needed to be kept small due to storage limitations. Data compression is needed to be shared with others. The Web and its underlying networks have inherent bandwidth restrictions which define the maximum number of bits or bytes that can be transmitted from one place to another in a fixed amount of time. OR Data compression is the process of encoding data to take up less storage space and less bandwidth for transmission. Digital data are compressed by finding repeatable patterns of binary 0s and 1s. The more patterns can be found, the more the data can be compressed. Text can typically be compressed to approximately 40% of its original size, and graphics files from 20% to 90%. Some files compress very little. It depends entirely on the type of compression algorithm used. As an example, the zip file format utilizes a common compression algorithm. Data compression has enabled information to be disseminated more rapidly.

Error Checking / Error Detection

Data that is transmitted over communication lines is subject to interference (noise) which can alter the nature of the data represented. Error checking protocols exist to check such errors and, if an error is detected the network, will try to recover the data, often by requesting a resend of the data packets.

Identify the technologies required to provide a VPN

Detailed: ------------------- 1. The first is a network access server (NAS, usually pronounced "nazz" conversationally). A NAS might be a dedicated server, or it might be one of multiple software applications running on a shared server. It's a NAS that a user connects to from the Internet in order to use a VPN. The NAS requires that user to provide valid credentials to sign in to the VPN. To authenticate the user's credentials, the NAS uses either its own authentication process or a separate authentication server running on the network. 2. The other required component of remote-access VPNs is client software. In other words, employees who want to use the VPN from their computers require software on those computers that can establish and maintain a connection to the VPN. Most operating systems today have built-in software that can connect to remote-access VPNs, though some VPNs might require users to install a specific application instead. The client software sets up the tunneled connection to a NAS, which the user indicates by its Internet address. The software also manages the encryption required to keep the connection secure. Simplified: ---------------- VPN are Virtual Private Networks that handle and transfer data as if it were private but by using public networks. This gives them the reach of large public networks (such as the Internet) while allowing users to keep their data secure and private. To set up a VPN, you need: A public network that at least two system can connect with Individual nodes must be connected to the network A VPN protocol

Describe encryption, authentication, and MAC address filtering.

Encryption is the process of encoding data sent wirelessly between your device and the router, essentially scrambling the information and restricting open access. There are three main types of encryption: WEP, WPA, and WPA2. Authentication Authentication is the process of determining whether someone or something is, in fact, who or what it is declared to be. In a wireless network authentication is commonly done through the use of logon passwords or passphrases.

Check sum

Error-detecting procedure that generates a sum from the digits of a number.

Flow Control

Flow control is utilized in data communications to manage the flow of data among two different network devices, especially in cases where the sending device can send data much faster than the receiver can digest.

Handshaking

Handshaking is a form of communication where a signal is sent from a device to another similar or dissimilar device(s).

ISDN

Integrated Services Digital Network - International communications standard that allows for the transmission of audio/video and other data over digital telephone lines.

TCP/IP Reference Model

Layer 1: Host-to-network Layer Lowest layer of the all. Protocol is used to connect to the host, so that the packets can be sent over it. Varies from host to host and network to network. Layer 2: Internet layer Selection of a packet switching network which is based on a connection-less inter-network layer is called a internet layer. It is the layer which holds the whole architecture together. It helps the packet to travel independently to the destination. Order in which packets are received is different from the way they are sent. IP (Internet Protocol) is used in this layer. The various functions performed by the Internet Layer are: Delivering IP packets Performing routing Avoiding congestion Layer 3: Transport Layer It decides if data transmission should be on parallel path or single path. Functions such as multiplexing, segmenting or splitting on the data is done by transport layer. The applications can read and write to the transport layer. Transport layer adds header information to the data. Transport layer breaks the message (data) into small units so that they are handled more efficiently by the network layer. Transport layer also arrange the packets to be sent, in sequence. Layer 4: Application Layer The TCP/IP specifications described a lot of applications that were at the top of the protocol stack. Some of them were TELNET, FTP, SMTP, DNS etc. TELNET is a two-way communication protocol which allows connecting to a remote machine and run applications on it. FTP(File Transfer Protocol) is a protocol, that allows File transfer among computer users connected over a network. It is reliable, simple and efficient. SMTP(Simple Mail Transport Protocol) is a protocol, which is used to transport electronic mail between a source and destination, directed via a route. DNS(Domain Name Server) resolves an IP address into a textual address for Hosts connected over a network. It allows peer entities to carry conversation. It defines two end-to-end protocols: TCP and UDP TCP(Transmission Control Protocol): It is a reliable connection-oriented protocol which handles byte-stream from source to destination without error and flow control. UDP(User-Datagram Protocol): It is an unreliable connection-less protocol that do not want TCPs, sequencing and flow control. Eg: One-shot request-reply kind of service.

What is the purpose of the OSI Model? (Second version, if you did not like the simplified version)

Layer 7: Application This is the layer that actually interacts with the operating system or application whenever the user chooses to transfer files, read messages or perform other network-related activities. Layer 6: Presentation This layer takes the data provided by the Application layer and converts it into a standard format that the other layers can understand. Layer 5: Session This layer establishes, maintains and ends communication with the receiving device. Layer 4: Transport This layer maintains flow control of data and provides for error checking and recovery of data between the devices. Flow control means that the Transport layer looks to see if data is coming from more than one application and integrates each application's data into a single stream for the physical network. Layer 3: Network The way that the data will be sent to the recipient device is determined in this layer. Logical protocols, routing and addressing are handled here. Layer 2: Data In this layer, the appropriate physical protocol is assigned to the data. Also, the type of network and the packet sequencing is defined. Layer 1: Physical This is the level of the actual hardware. It defines the physical characteristics of the network such as connections, voltage levels and timing.

Bus topology

Network configuration wherein all computers connect to the network via a central bus cable.

Congestion

Network devices have a memory location called a buffer that is used to store data that has been sent to them from another source. If this buffer becomes full and cannot handle any more data a problem known as congestion occurs.Congestion occurs when the source sends more data than the destination can handle. When this congestion occurs performance will degrade.

VLAN

Network form by several LANs which are in separate geographical locations. It restricts each network from other unless the connectivity in some form is configured. Virtual local area network - A group of network devices that are on the same LAN but are geographically distributed. -Virtual LAN -Behave as if they were connected -Actually in different locations -Through SOFTware not HARDware

What is the purpose of the OSI Model?

Networks are broken down into 7 layers known as the OSI Model: Physical -->This layer consists of the physical components that make up a system and convert bit streams (electrical impulses) into data usable by the system. Data Link -->This layer encodes data packets into bits. This is the layer in which different types of transmission protocol. Both Media Access Control (MAC) and Logical Link Control (LLC). MAC- This controls how a computer on a network gains access to data and permissions to transmit it. LLC- This controls frame synchronization, flow control and error checking. Network -->This layer provides switching and routing techniques, creating virtual circuits, to transmit data from node to node. Transport -->This layer is responsible for controlling data flow between end systems, or hosts. Session -->This layer manages sessions and the interactions between different applications in a session on a system. Presentation -->This layer translates data from application format to network format and vice versa. Application -->This layer handles interactions with users and supports end-user processes as well as applications.

Data packet

Part of a transmitted message that is sent separately. Apart from containing a portion of the message it will have other data such as check digits, destination address and so on. OR A data packet contains data traveling over a network. It is a basic unit of binary data for communication over a digital network. OR Data packet: how data travels over the internet; it travels in small packets

Why are protocols important for networking?

Protocols are necessary as their function is to allow two or more devices to be able to interact with each other and are a method of neutral mediation. Protocols do not need to be public, and can be kept confidential. Network protocols are also necessary because they contain mechanisms which allow devices to identify and make connections with each other, they can also format rules which specify how data is packaged into messages sent and received. Protocols also support message acknowledgement and data compression which are designed for reliable and/or high-performance network communication, for instance, hundreds of different computer network protocols have been developed each designed for specific purposes. Protocols in communications are needed because they contain rules that describe behavior, it would be difficult to communicate between devices without protocols. Without a set of rules, computers would not have the capability of communicating to each other across the Internet; these certain protocols help computers identify themselves on a network such as the Internet.

Outline the importance of standards in the construction of networks.

Standards enable compatibility through a common "language" internationally. Allows the interoperability among different computer hardware. Allows a set of rules in order for the networks to function properly throughout the world due to the fact some countries might not have access to advanced technology and will still have to access the world wide network. --> A network protocol is a standard set of rules and procedures for computers to use when communicating with one another.

Data integrity

The accuracy of data after input, transmission, storage or processing. OR Data integrity, in the context of networking, refers to the overall completeness, accuracy and consistency of data. Data integrity must be imposed when sending data through a network. In other words, how does a computer know that when it receives data over a network that it is complete, accurate, and consistent. This can be achieved by using error checking and correction protocols.

Alternative Description of WIFI,WIMAX, 3G and 4G

Wi-Fi Is short for wireless fidelity The standard for Wi-Fi today is 802.11 Creates local area networks that device with internet can connect to Maximum range is and eighth to a quarter of a mile Speed is 11Mbps or greater WiMax Was designed to make high quality, long range data and voice communications affordable Maximum range is 3-5 miles Speeds from 4Mbps to 6 Mbps 3G It is the third generation of mobile networking Download speeds of 14.4 Mbps and Upload speeds of 5.8 Mbps Minimum speed for stationary user is 2 Mbp Future 4G Speed can be up to 100 Mbps Is compatible with a vast array of devices Access to services anytime anywhere

Describe the characteristics of wireless networks. WIFI, WiMAX, 3G, 4G

WiFi Wireless network that uses radio waves to transmit and receive data. Effect range relatively short, about 65 ft. Currently has higher average data speeds compared to other wireless network technologies (WiMax, LTE). Speed is effected by interference and distance from router. Easy setup. WiMax (Worldwide Interoperability for Microwave Access) It is similar to Wi-Fi, but it can enable usage at much greater distances. Provides a wireless alternative to cable, DSL, and satellite Internet service. It is essentially a wireless broadband. ISPs can deliver Internet connections without running expensive cables to every home, and speeds often run between 5-10Mbps. Primarily due to its much higher cost, WiMAX is not a replacement for Wi-Fi home networking or Wi-Fi hotspot technologies. Current WiMax availability is limited. WiMax lost out to the competing LTE technology in the cell phone industry. 3G mobile "3rd Generation" cell phone technology first avaliable in cell phones in 2003. Depending upon carrier 3G networks use either EDGE, EV-DO or HSPA data protocols. Speeds range between 400 kilobits and 2Mbps, depending on the carrier and region. 4G mobile "4rd Generation" cell phone technology first avaliable in cell phones in 2008. Depending upon carrier 4G networks use either Wi-Max, HSPA+ or LTE data protocols. Most carriers have moved or are moving to LTE. Speeds currently range between 3.5Mbps and 19Mbps, depending on the carrier and region. There is currently very little standardization in 4G technologies. In some cases, one company's 4G speeds could be inferior to another carrier's older 3G network.

Wide Area Network

Wide Area Network; largest type of network in terms of geographic area; largest WAN is the Internet

WLAN

Wireless Local Area Network

Describe the hardware and software components of a wireless network

Wireless router - A router is network device that determines where data packets should go and sends them to their destination by the shortest, most efficient route. A wireless router is a router that uses radio waves to transmit data. Wireless adapter - A wireless network adapter connects a computer to a wireless network so that they can communicate. Virtually all laptop and smaller computing units come with a built-in wireless adapter. If you want to convert your desktop computer to a wireless unit, you have to obtain a wireless adapter. The adapter slips into a slot inside the computer, with an antenna that projects out the back of the computer. You can also buy adapters that plug into a usb port. Extender - Wireless networks have a finite range. If you find that your signal is not strong enough to cover the areas you want, a wireless extender can fix the problem. A wireless extender captures the router signal and rebroadcasts it. Plug your extender into a wall socket about halfway between the router and where you are having difficulty picking up the wireless signal. Software Router Software - routers contain built-in software that can be accessed using any web browser software. This software is used to configure the router. You can perform tasks like assigning a router's SSID and setting security and firewall parameters.

Parity bit

a bit that acts as a check on a set of binary values, calculated in such a way that the number of 1s in the set plus the parity bit should always be even (even parity) or should always be odd (odd parity).

Server

a computer or computer program that manages access to a centralized resource or service in a network.

Network

a group of two or more computer systems linked together

Storage Area Network

a high-speed network with the sole purpose of providing storage to other attached servers -Storage Area Network -Accesible by multiple computers -Hard drives in SAN, as if the computers were all locally attached to it. -Easy to share information. -Servers

Packet switching

a mode of data transmission in which a message is broken into a number of parts that are sent independently, over whatever route is optimum for each packet, and reassembled at the destination. Group of bits. May include control signals, error control bits, coded information, as well as the destination of the data.

Packet

a single unit of binary data routed through a network

Microwave transmission

a wireless system that uses microwaves for high-volume, long-distance, point-to-point communication

Explain why speed of data-transmission across the network may vary?

ere are some causes of lag: Length of the route that the packets have to take between sender and receiver. Type of media transporting the data.(e.g. fiber optics, satellite, wireless, metal wiring) Network congestion - causes data to be retransmitted. Traffic load - how many people are using network. Time of day - people use network more during peek times. Weather - satellite and wireless signal interference.