WEEK 4: COMMUNICATIONS AND NETWORKS Flashcards
(22 cards)
What is a computer network?
Computer network - consists of two or more computing devices that are connected to each other. This is to pass information and share resources.
-> can start with only two computers, and as more devices join in, the network becomes bigger.
What is a communication system and what are the four basic elements?
- Involves electronic systems that exchange data from one location to another.
- Data transmission can be made through a wired or wireless connection.
Four basic elements of a communications system:
- > Sending and receiving devices.
- > Communication devices.
- > Communications channel.
- > Data transmission specifications.
This is how a communication system functions with its elements.
Sending device -> modem -> communication device -> packets of a communication channel -> communication device -> modem -> receiving device.
What are sending and receiving devices?
- All types of computers and mobile devices acts as sending and receiving devices in a communications system.
Eg. personal laptop, printers, game consoles, mainframe computers, servers, etc.
What are communication devices?
- Hardware that is capable of transferring data or information between a sending and receiving device.
- At the sending point, a communication device relays the signal from the sending device to a communications channel.
- At the receiving point, a communications device accepts the signal from the communications channel.
- Signals can be digital or analog signals, based on the channel used.
What are modems?
Modem is short for modulator and demodulator.
- Converts digital signals to analog signals and vice versa.
- Modulation - convert from digital to analog.
- Demodulation - convert from analog to digital.
- Speed of a modem is called data transfer rate or the symbol bit/s, sometimes abbreviated “bps”.
- Modern broadband modems are typically described in megabits.
Telephone lines relay and accept analog signals. Computers only relay and accept digital signals.
What are the types of modems?
- > Dial - up modem.
- > DSL or Digital Subscriber Line modem.
- > Cable modem.
- > Wireless modem.
How does a communication channel function?
- Carry the data from one comp to the other; essential element of every communication system.
- Physical and Wireless Connections.
What are the physical connections?
- > Twister pair cable - two pairs of copper wire are twisted together.
- up to 1Mbps to 10Gbps.
- Telephone lines, Ethernet cables.
- > Coaxial cable - single solid copper wire.
- 80X more transmission capability than twister pair cables.
- Television cable.
- > Fibre optic cable - bundle of glass threads that use light to transmit data.
- 40 Gbps / 26,000X more transmission capability than twisted pair cables - but also a much higher cost.
- Widely used in high speed communications system.
What are the wireless connections?
Infrared - use infrared light waves.
-> Within the range of 10 feet and in straight line.
Bluetooth - short range radio technology standard.
-> Range of 10 meters or 33 feet.
WiFi - uses radio wave to provide wireless high speed internet and network connections. Based on IEEE standard 802.11x.
-> Widely used in home, schools, campus and offices.
WiMAX (Worldwide Interoperability for Microwave Access) - use microwave connections to extend Wifi range. Based on IEEE standard 802.16.
-> Long-range wireless networking spanning distances miles or kilometers away.
LTE (Long Term Evolution) - cellular wireless connection, synonym to 4G for marketing purposes.
-> Theoretically data speed are 10 times faster than 3G.
Cellular radio - wireless transmission media that are used for mobile devices and mobile phones to transfer voice and data.
-> As long as a mobile phone in the network coverage is within a cell.
Microwave - used radio waves; a microwave transfer signal to another via straight line.
-> Installed on top of a building, towers or hills to avoid any obstruction.
Satellites - specialised wireless receiver-transmitter and sent to space by rocket and stationed in orbit around the earth.
-> More than 2000 satellites in orbit which was used by both government and private organisations.
What are some communication services?
- Service provider that provides infrastructures for information to be transported from one device to another or through a network on the internet.
- > Leased Line - Telekom Malaysia.
- > Fiber-optic Service - Fibre Comm.
- > Satellite Connection Service - Thuraya.
- > Cellular Service Providers - Celcom, Maxis, Digi.
How did the revolution of the cellular radio progress?
1980s 1G - analogue voice calls; mobile connectivity.
1990s 2G - digital voice calls; text messaging; basic data services.
2000s 3G - mobile broadband; introduction of smartphones.
2010s 4G - fast mobile broadband; uses internet protocol.
2020s 5G - enhanced mobile broadband; wireless for the industry.
Why do computers need IP Addresses?
- Networks, and the internet, does not identify computers by the name user assigned to them.
- Computers prefer numbers, and the numbers they use as identifiers are called IP addresses.
- IP stands for “internet protocol” which is part of Transmission Control Protocol/internet Protocol (TCP/IP). IP for short and ICP/IP is how data is delivered.
- Domain Name Server (DNS) translates domain name into IP address.
Examples of IP Address - 255.255.255.255; to check = command prompt -> ipconfig.
What are the specifications of data transmissions?
- Refers to the rules and procedures that coordinate the message transmitted between sending and retrieving devices across the channel.
- Several factors that affect data transmission which include bandwidth and network protocol.
Bandwidth
- > Refers to the amount of data that can pass through the communication channel in a given amount of time.
- > Measured in bits per second, most internet connections have a bandwidth on the scale of megabits per second.
Network protocols
- > Sets of established rules that dictate how to format, transmit and receive data.
- > From servers and routers to endpoints.
- > Transmission Control Protocol or Packetization is the process whereby:
- Information are broken up into smaller packets.
- Travel on different route (fast transmission).
- Reassembled at the destination.
What is a network?
- Interconnection between all devices in a network.
- Individual devices are known as a node.
- Computer not part of a network is called a stand alone computer.
What are some basic network terms?
Nodes - any device connected to a network; laptop, printers, servers.
Clients - computers that access and use the network and share network resources.
Host - when there are two computer systems connected by modems and telephone lines.
- > System that contains the data is the host.
- > While the computer is at where the user requested data it is called the remote terminal.
Servers - computers that hold shared files, programs, and the one installed with network operating system.
Network administrator - person who is responsible to coordinate, maintain and ensure that a network is in an organization that is running smoothly and is up to date.
What are some basic network terms?
Nodes - any device connected to a network; laptop, printers, servers.
Clients - computers that access and use the network and share network resources.
Host - when there are two computer systems connected by modems and telephone lines.
- > System that contains the data is the host.
- > While the computer is at where the user requested data it is called the remote terminal.
Servers - computers that hold shared files, programs, and the one installed with network operating system.
Network administrator - person who is responsible to coordinate, maintain and ensure that a network is in an organization that is running smoothly and is up to date.
What are the advantages of a network?
1) Sharing resources: network makes it easy for everyone to access the same file and work on it together
2) Communication and collaboration: allows employees to share files, view other people’s work, and exchange ideas more efficiently.
3) Organization: variety of scheduling software is available that makes it possible to arrange meetings without constantly checking everyone’s schedules. Software includes other helpful features - shared address books and to-do lists.
4) Remote access: users are able to access the same file, data and messages even when they’re not in the office. This access can even be given to handheld devices.
5) Data protection: important task to back up a computer data regularly. Network makes it easier to back up all the company’s data at once, either to put them on an offsite server, a set of tapes, CDs or other backup system.
What are the different types of networks?
Personal Area Network (PAN) -
covers a very small area, connects devices within a certain range and if a user moves outside that range, connection can be lost.
-> Connecting a smartphone to a laptop, tablet or other wireless devices.
Local Area Network (LAN) - computer network that links devices within a building or group of adjacent buildings. Especially with a radius less than 1km.
-> WLAN allows devices to communicate via WiFi but still within certain range.
Wireless LAN (WLAN) - LAN without using cables; alternative to a LAN that uses Ethernet cables.
- > Common in an office or large campus; wireless access point is used.
- > Any node that has a wireless connection devices such as a wireless network card will get into the WLAN by receiving the broadcast signal from the wireless access point.
- > WLAN would normally need a strong password - to avoid anyone from using it without permission.
Metropolitan Area Network (MAN) - used to link between office buildings in a city; comprises of several LANs working together.
- > Covers larger area than a LAN but smaller area than a WAN.
- > MAN may span in the range of 5 to 50 km in diameter.
- > MAN is operated by a service provider that provinces an Internet connection or cable television to a city.
Wide Area Network (WAN) - exists over a large-scale geographical area.
- > Biggest and widest network.
- > Connects all over the world.
What are the hardware requirements for a Network?
Network interface card - connects computers to a local data network or the internet.
Network access point - a device that connects to a wired router, switch, or hub via an Ethernet cable, and projects a Wi-Fi signal to a designated area.
Wireless access point - device that broadcasts radio signals so that other wireless devices can receive the signals in order to access the network and the Internet.
- > Allows data from wireless devices to be transferred to wired devices.
- > Important to position the wireless access point at a strategic place so that surrounding devices can capture the signals.
Router - device that forwards data packets between computer networks - can connect networked computers to the Internet, so multiple users can share a connection.
Hubs - contains multiple ports - when a packet arrives at one port, it is copied to the other ports so that all segments of the LAN can see all packets.
-> Only suitable for small networks.
Switch - device in a computer network that connects other devices together.
-> Multiple data cables are plugged into a switch to enable communication between different networked devices.
There are three types of “nets” in an organizational network, what are they?
Intranet - private network, owned by a large company.
-> Only authenticated users of the organization can access the database system, directory and can distribute documents and workflow.
Extranet - private network designed to allow business partners and vendors to communicate in a virtual space.
Internet - largest network in the world.
What are the things that you could install to protect your network?
Firewall - system designed to prevent unauthorised access to or from a private network.
- Monitors and controls the incoming and outgoing network traffic based on pre-setting rules.
- Performs actions such as blocking or filtering traffic before entering a private network.
- Eg. A company may limit the size of an attachment file from an incoming email. If the size is greater than the set rules, the email will bounce back to the sender.
- Can be hardware or software-based or both; should be placed at the first line of defense of any network.
IDS - also known as an intrusion detection system; software or hardware that analyses all network traffics.
- All devices connected to the network are being monitored by the system.
- Detects and alerts a system administrator to stop the suspicious attack.
- Alert goes to central system, log will be used to investigate whether a malicious activity was going on or it was a false alarm.
- Should be placed after the firewall.
Virtual Private Network (VPN) - secures connection over the internet between the employee’s computer and the company’s network.
- The user has access to the remote network after validation of credentials.
- Safer than using public network.
