Networks and the effects of using them

Network devices

Modems (modulator demodulator) A device that converts a computer’s digital signal into an analogue signal for transmission over an existing telephone line. Used to allow computers to connect to networks over a long distance using the existing telephone networks.

Hubs Hardware devices that can have a number of devices or computers connected to them. Used to take any data packet (a group of data being transmitted) received at one of its ports and broadcast it to every computer in the network. Often used to connect together a number of devices to form a LAN-for example, a star network

Switches Similar to hubs but are more efficient in the way that they distribute data packets. Check the data packet received and works out its destination address and sends the data to the appropriate computer(s) only. Each device or computer on a network has a media access control (MAC) address that uniquely identifies it.

Bridge Devices that control one LAN to another LAN that used the same protocol (communication rules) Used to connect together different parts of a LAN so that they can distribute as a single LAN.

Router Enable data packets to be routed between the different networks, for example to join a LAN to a wide area network (WAN). Have an internet cable plugged into it and several cables connecting to computers and other devices on the LAN. Broadband routers sit behind a firewall which protects the computers on a network. The router transmits internet and transmission protocols between two networks and allows private networks to be connected together.

Data packets The data is carried in the packet according to which protocol is used. -the identify number of each packet This info allows the router to route a packet across a network to its correct destination and allows the data packets to be reassembled in their correct order. Usually contain: -Some form of header to identify the data packets -Sender’s IP address -Receiver’s IP address -How many data packets make up the whole message.

Gateway A network point (or node) that acts as an entrance to another network. A key point for data on its way to or from the other network

Network interface card (NIC) Is needed to allow a device to connect to a network. Usually part of the device hardware and frequently contains the MAC address generated at the manufacturing stage.

Networks cables Even though many computer system use Wi-Fi, network cables Wi-Fi, network cable are still used because: -Faster data transfer rates -Can be more secure than a wireless networks

Internet protocol (IP) and media access control (MAC) addresses

Each device on the internet is given a unique address known as its internet protocol (IP) address. A MAC address is a unique number that identifies a device connected to the internet

Differences between IP addresses and MAC addresses Gives the location of a device on the internet Identifies the device connected to the internet

Wi-Fi and Bluetooth Both Wi-Fi and Bluetooth offer wireless communication between devices. They both use radio frequencies as the carrier of data transmission.

Wi-Fi A wireless transmitter (WAP) receives info from a network via its connection. This transmitter converts the info into radio waves and then transmits them. A device(e.g. a computer) receives the radio waves via an installed wireless adaptor which allows it to download the info from the data resource. This, of course, works in the reverse when the device wishes to transmit data over the network. Wi-Fi offers much faster data transfer rates, better range and security than Bluetooth.

Bluetooth Bluetooth sends and receives radio waves in a band of 79 different frequencies(known as channels). These are all centered on a 2.45 GHz frequency. Devices using the Bluetooth automatically detect and connect to each other, but they don’t interfere with the other devices since each communicating pair uses a different channel When a device wants to communicate, it picks one of the 79 channels at random. If the channel is already being used, it randomly picks another channel (a.k.a spread-spectrum frequency hopping) Useful: when transferring data between two or more devices that are close together, for low-bandwidth applications

Differences between Wi-Fi and Bluetooth Transmission frequency: 2.4, 3.6, 5.0 GHz Max data transfer rate: 250 Mbits/second Max effective range: 100m Max number of devices connected: depends on the router used (one or many) Type of data transmission security: WEP (wireless equivalent privacy) and WPA (Wi-Fi protected access) Transmission frequency: 2.4 GHz Max data transfer rate: 25 Mbits/second Max effective range: 30m Max number of devices connected:7 Type of data transmission security: key matching encryption

How to set up and configure a small network Setup an IP account if internet is required Set up the system Configure all the hardware and software Setting up privileges so each user can only access their own area Ensure high-speed broadband connection exists if needed internet Put all software in one server Set up a network-manager-level of privilege do that they can monitor network usage, change passwords, etc

Local area network (LAN) These systems are usually within one building/ not very far from each other. Consists of a number of computers and devices(for ex, printers) that are connected to hubs /switches. One of the hubs/switches will usually be connected to a router and a modem to allow the LAN to connect to the internet, in doing so it then becomes part of a WAN

Advantages: -ease of communication between the users. -a network administrator to control and monitor all aspects of the network Disadvantages: -easier spread of viruses throughout the whole network -if the main server breaks breaks down, in most cases the network’ll no longer function

Wide area network (WAN) Are used where the computers or networks are situated a long distance from each other If a number of LANs are joined together using a router or modem, then they can form a WAN. Ex: the internet and the network of the ATMs used by the banks

Wireless LANs (WLANs) Are similar to LANs but they provide wireless network communications over fairly short distances using radio or infrared signals Devices, a.k.a access points (APs), are connected into the wired network at fixed locations. Because of the limited range, most commercial LANs need several APs to permit uninterrupted wireless communications. The APs use either spread spectrum technology (wideband radio frequency with a range of 30-50m) or infrared (has a very short range and easily blocked)

Advantages: Disadvantages: -As there is no cabling there is a safety improvement and increased flexibility (since the user no longer has to remain at their desk) -Security can be a big issue since anyone with a WLAN-enabled laptop can access a network if it can pick up a signal -Data transfer rate is slower than in a wired LAN -Adding new computers and devices is very easy, costs are reduced since extra cabling isn’t needed.

Accessing the internet

Mobile phones and tablets Portable, can be used almost everywhere provided a mobile phone network signal can be accessed Expensive to use if the Wi-Fi hot spot is not available Display are small Keyboards are small People is more likely to have their phones at all times Not all websites are mobile-friendly Signal less likely to be as stable or reliable as a wired system Easier to use a phone while on the move

Laptops More mobile than desktops Screen size is smaller than desktops Touchpads are not as easy to use as a mouse but easier than phones Processors are not as powerful as desktops’ so access speed is not as quick Keyboards are not as easy to use as desktops but are better than phones

Desktop computers More powerful/faster processor than other devices Full-size keyboard and pointing devices make web page navigation much easier Have more stable and reliable internet connection since they use a wired system rather than Wi-Fi Not portable Require expensive ‘dongles’ to access the phone network Large screen

Should the internet be policed? Arguments in favor of some control: -Prevent illegal info to be posted -Easier to find info that can have serious consequences -Prevent kids and other vulnerable groups from being subjected to undesirable sites Arguments against some control: -Info posted on webs is already available form the other sources -Expensive to ‘police’ all sites and users would have to pick up the bill -Difficult to enforce the rules and regulations on a global scale

Inappropriate sites and the accuracy of info Three aspects to consider when looking at the quality of info found on a search engine: -Reliability of info -Undesirability of certain websites -Security issues

Reliability of info Info on the internet is more likely to be up to date than in books Easier to get info from websites Large amount of info on the internet that is easier to locate than using books Info could also be incorrect since it doesn’t go through any checking

Undesirability of certain websites Risk of finding undesirable webs Risk of connecting to webs that are not genuine, which could lead to problems Security risks

Security issues Passwords are used when: -accessing email accounts -carrying out online banking -accessing social networking sites It’s important that passwords are protected and here are some ways: -run anti-spyware software -change passwords on a regular basic -passwords should not be easy to break or guess

Authentication Is used to verify that data comes from a secure and trusted source. User IDs and passwords are authentication technique. Some forms of authentication include: -digital certificates -biometrics -magnetic stripe cards/id cards/passports

Antivirus software Antivirus software will constantly check for virus attacks Common features : -check software/files before run or loaded -compare a possible virus against a database of known viruses -carry out heuristic checking- checking of software for types of behavior that could indicate a possible virus -files that are affected are put into quarantine that: allows the virus to be automatically deleted or allows user to make decision -antivirus software needs to be update since new viruses are constantly being found

Avoiding viruses when accessing the internet Avoid unknown or suspicious-looking webs Look for the security indicators as https or the padlock symbol Not advisable to open emails /attachments from unknown sources

Viruses from hardware devices It’s possible to pick up viruses from any device plugged into your computer

Data protection acts Guidelines about how stop data from being obtained unlawfully: -don’t leave personal info on a desk -lock cabinets at the end of the day -log off your computer if away from your desk -use hard-to-guess password and user ids

Network communication

Faxes Two basic ways to send a fax: A physical fax A electronic fax (modern way) The only difference is electronic faxing is always associated with an email address and a fax number

Emails Useful when sending attachments Can be sent to or from any device connected to the internet

Video conferencing Basic hardwares: -webcams -large monitors -microphones -speakers Advantages: -possible to hold meetings at short notices -not travelling physically reduces costs

Audio conferencing Equipment needed: telephone/internet phone/computer with built-in speakers and microphone

Web conferencing Uses the internet to permit conferencing to take place Multiple computers are used Only needed computer with high-speed and stable internet connection To carry out web conferencing, users have to use an application or website from the conference organizer.