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The Networking and Internet Basics - Coggle Diagram
The Networking and Internet Basics
Basic concepts of Computer Networks
✧ A system of interconnected computers, peripherals and communication devices that can exchange information and share resources.
✧ Networking is widely used in government departments, corporations, educational institutions and homes.
✧ Internet - the world’s largest computer network connecting billions of computers together around the world
Local Area Networks (LANs) and Wide Area Networks (WAN)
Networks are categorised according to the area they cover .
Local area network (LAN)
A network that connects computers within a relatively limited area
Consists of networked computers, or workstations, shared peripheral devices, communication devices and links.
Two popular types of LANs:
Peer-to-peer(P2P) network
⬥ A network of workstations without a server
⬥ All the workstations can communicate directly with each other.
⬥ Each computer can access the resources which are shared by all the other peer workstations.
⬥ Usually has a small number of workstations.
⬥ Cost of setting up is relatively low.
⬥ Usually found in small companies and homes.
Client/server networks
⬥ Client workstations are connected to a central server, or a host computer.
⬥ Clients can access the resources stored on the server.
⬥ The set-up cost is relatively high.
⬥ It provides better security controls and
network services in a large-scale network environment.
Wide Area Network (WAN)
A network that spans a wide geographical area.
Refers to a communication network that spans a large geographical area, across regions or continents.
Consists of two or more remote LANs.
LANs are connected via different communication channels:
⬥ Telephone lines
⬥ leased lines
⬥ Microwave
⬥ Satellites
⬥ Optical fibre cables
Network Services
When a computer is connected to a network, it can provide more extensive services.
Major services provided by a network are:
Internet access service sharing
● Users can access the Internet via a computer network with a single Internet service account
● Can reduce the cost of Internet access
● Helps Monitor, control and protect network communications with the external parties through the Internet.
Information backup
● Information on individual computers can be backed up and stored on a server via the network.
● These backup files can be used to recover lost information in an out-of-order computer in a few minutes
Centralised data management
● All data centralized in one network server
● All authorized users are able to share the latest and identical information all the time.
● Allows many users to work on the same project at the same time.
● Increasing productivity and efficiency
● Better than duplicate and scatter important data files and sensitive information onto many different computers
● No data update problems.
● Reduce management costs
● Less vulnerable to security attacks
Apply a number of security measures to protect the network from intrusions through the Internet.
● Once the network allows the Internet access:
⬥ Possible for a remote user to access a network server
⬥ Risk of attack from hackers
Software sharing
Application software can be shared simultaneously among computers on a network.
A network licence:
⬥ Allows multiple legal access to the software.
⬥ Usually sets a limit on the number of users who use the program simultaneously in the network
⬥ Cost is usually lower than the total cost of individual software licenses.
⬥ No need to carry out software installation on each computer
⬥ More efficient
Hardware sharing
In a LAN,
⬥ Users are allowed to share hardware resources such as hard disks, printers and scanners.
⬥ Shared equipment can be better monitored and utilized.
⬥ Helps save and cost of extra hardware.
In a WAN,
⬥ Sharing of hardware is less common except for the hard disk storage space.
⬥ After logging onto a file server, a user can upload and download files from a dedicated folder on the file server.
Network conferencing
● The technology that enables users in two or more locations to communicate with each other via two-way audio audio and video signals
● Video signals must be compressed before they are sent through a computer network.
Internal communication
In both LAN and WAN, users can communicate with each other by email, instant messaging or file transfer.
Connecting to a Computer Network
Network Interface Card (NIC)
Media access control (MAC) address
⬥ Each NIC’s unique hardware number
⬥ Identify the computer on the network.
⬥ Burnt onto the NIC by the manufacturer
Classified by:
⬥ Types of connectors
⬥ Expansion buses
⬥ Size of its bandwidth
An expansion board for connecting a computer to a network
Network connecting devices
Repeater
● A device that amplifies the received signals
● Removes unwanted noise
● Sends the amplified signals to the connected device.
● Overcomes the problem of signals attenuation due to the long distance transmission.
Bridge
● Often used to interconnect two or more LANs of the same type
Hub
● Similar to switch
● Can only handle low transmission traffic
● Its efficiency drops significantly under heavy network traffic
● Cost is very close to switch
Router
● A device that translates from different networks
● Usually responsible for the connectivity between different types of LANs and between a LAN and the Internet.
● Home-use routers = switching routers
● Work as both a router and a switch
● Users can connect two or more computer to the broadband modem and form a small network.
● Not very reliable and durable
● Incapable of handling large volumes of data traffic
Switch
● Provide a central connection point for cables on a network.
● In a typical network configuration, one or more computers are connected to a switch via network cables.
● Connected to a server with typical data transmission speed of 10 Mbps, 100 Mbps and 1 Gbps
Modem
● A dial-up modem is used when a computer is connected to other remote computers via telephone lines.
● Converts signals between digital and analogue form.
● Can be installed internally or externally.
● Internal modems are either in the form of an expansion card or built as a part of the motherboard.
● External modems are single devices that can connect to the connection port of a computer system.
● Maximum data transmission speed is 56kbps
● cable modem
⬥ Used when the broadband service is provided via a cable TV line.
⬥ Modulates the digital computer network data into
radio- frequency signals for transmission.
⬥ Demodulates incoming radio-frequency signals into digital signals.
Digital subscriber line(DSL) modem
⬥ Used when broadband service is provided via a residential telephone cable.
⬥ Filters DSL signals from telephone voice signals.
⬥ Converts incoming signals that a computer can process and vice versa.
Network cables
Coaxial cable
● Commonly used for VCR and cable television connections.
● Has a BNC connector on both ends.
● Higher ability to retain the strength of a transmitting signal over a long distance than a twisted-pair cable
● Consists of:
⬥ a copper wire
⬥ a sheath of insulation
⬥ a wire mesh that conducts and shields against interference
⬥ an outside coating
● Strengthened insulation allows coaxial cables to transmit more information than twisted-pair cables.
Optical fibre cable
● Made of a bundle of glass threads that transmit light beams
● Advantages:
⬥ Significantly greater signal-carrying capacity
⬥ Faster data transmission
⬥ Reduced susceptibility to noise or interference from other devices
⬥ Better security for signal transmission
⬥ Much thinner, lighter and more durable
● Largely replaced coaxial cables in telephone networks.
● Disadvantages:
⬥ Cost is very high
⬥ Installation process is much more difficult than that of other network cables.
⬥ Special device is needed to convert digital signals to optical light beams and vice versa.
⬥ Once installed it can hardly be changed.
Twisted-pair cable
● Widely used in local area networks.
● Looks similar to a telephone cable and has an RJ-45on both ends.
● Wounding two conductors together = eliminate electromagnetic interference from external sources.
● Two types:
a. Shielded twisted-pair(STP) cable
⬥ Has a metal wrapper around each wire to reduce noise and electromagnetic interference
b. Unshielded twisted-pairUTP cable
⬥ Does not have metal shielding
⬥ Lost-cost substitution for the STP cable
⬥ Maximum data transmission speed of Cat 6 UTP cable is about 1,000 Mbps within 100 m distance limit.
Radio connections
Microwave broadband
● Communicates with the ISP by a microwave signal.
● Broadband subscriber and the ISP sends and receive radio signals directly to each other.
● Consists of a number of access points and subscriber units.
● Access points
⬥ Mounted on top of buildings since each subscriber unit must have a line-of-sight to the access point
⬥ Practical coverage: up to 1.5 km
⬥ Data transmission speed: up to 100 Mbps
● May be affected by rainstorms and connections may become unstable or even break up.
Wi-Fi connections
● Wireless fidelity (Wi-Fi)
⬥ The network based on the IEEE 802.11 wireless local area network (WLAN) standard
● Data is transmitted by radio waves
● Any two Wi-Fi-enabled devices can create a wireless connection to communicate with each other.
● To transmit data:
⬥ The sender translates digital data into radio signals and transmits it to the receiver
⬥ The receiver then translates the received radio signals back to digital data
● Widely used in building WLANs
● WLAN
⬥ Uses high-frequency radio waves to transmit and receive data.
⬥ Providing all the features and benefits of wired LAN technologies.
⬥ Without the limitations of cables
⬥ Can be connected to a wired LAN by means of an access point
● Access Point
⬥ A device that allows a wireless device to communicate to other wireless devices by radio frequencies
⬥ Or communicates to a wired network by converting digital signals to radio frequencies and vice versa.
● To connect a device to WLAN
⬥ Must be equipped with a wireless network interface card
⬥ Placed within the radio signal region on an access point.
● Advantages:
⬥ Cost of building up a network is lower.
⬥ Network structure can be modified if required.
⬥ A network can be extended to an outdoor area
● Disadvantages:
⬥ Effective data transfer rate is highly affected by the surrounding environment
⬥ The risk of intrusions is higher
⬥ The maximum data transmission speed of a WLAN is significantly lower than that of a wired network.
⬥ The coverage of a wireless router or access point is limited.
⬥ The cost of building up a large wireless network can be very high
Satellite broadband
● Can be used to establish a connection to the Internet in remote areas where wired broadband is not available.
● Requires a dedicated satellite and a satellite dish on each end of the connection.
● Average upload and download speeds are around 50Kbps and 500Kbps respectively.
● Despite the low transmission speeds, the set-up cost and the monthly charge can be very expensive
Methods of Internet Access
Integrated Services Digital Network (ISDN)
● ISDN works on the same principle as a dial-up connection
● Need an ISDN connected to a conventional telephone line to establish an ISDN connection to the ISP server.
● Maximum data transmission speed: 128 Kbps
● Data is transmitted as digital signals instead of analogue signals.
⬥ More stable and less likely to be affected by surrounding interference
● Greatest network coverage among all broadband connections
● Gap of transmission speed of ISDN is slower than other popular broadband connections
broadband connections
Dial-up connection
● Basic equipment:
⬥ Dial-up modem
⬥ A telephone line
● Probably the cheapest option of infrequent Internet users.
● It charges are either fixed or based on usage time
● Necessary software for Internet access:
⬥ A web browser for viewing web pages
⬥ An email program for receiving and sending emails
⬥ Communication software for establishing a connection with the ISP
T-carrier
Internet service provider
● To access the Internet with your computer:
⬥ Register an account with an Internet service provider(ISP)
⬥ Set up necessary computer equipment
⬥ Install appropriate software and then establish a connection
● An ISP is a company that provides Internet access services
● It usually offers subscribers a communication software package for establishing a connection with the ISP server.
● Data transmission speed or bandwidths vary from 56 Kbps to 1,000 Mbps.
Wireless Internet access
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