Chapter 2 - Networking Flashcards
ARPAnet
Advanced Research Projects Agency network
WAN
Wide Area Network (network covering a very large geographical area)
Typically consists of LANs connected via public communications networks
This means it may be a private network and passwords/user IDs are required to access it
LAN
Local Area Network (network covering a small area such as a single building)
MAN
Metropolitan Area Network
Larger than LAN smaller than WAN
File server
Server on a network where central files and other data are stored and can be accessed by a user logged onto the network
Hub
Hardware used to connect together a number of devices to form a LAN that directs incoming data packets to all devices on the network
Switch
Hardware connecting a number of devices to form a LAN that directs incoming data packets to a specific destination address only
Router
Devices which enables data packets to be routed between different networks (eg. can join LANs to form a WAN)
Modem
Modulator demodulator
Device that converts digital data to analogue data (to be sent down a telephone wire), also converts analogue data to digital data. Allows several simultaneous wireless connections to take place without interfering with each other. Connects to public infrastructure (cable optic fibre etc.) and supplies a standard Ethernet output which allows connection to a router and internet connection.
WLAN
Wireless LAN (local area network)
(W)AP
(Wireless) Access Point
Access point which allows a device to access a LAN without a wired connection
PAN
Network that is centred around a person/their workspace
Client server
Network that uses separate dedicated servers and specific client workstations, all client computers are connected to the dedicated servers
Spread spectrum technology
Wide and radio frequency with a range of 30 to 50 metres
Resistant to blocking/tracking as the frequencies change constantly
Node
Device connected to a network (can be computer, storage device or peripheral device)
Peer-to-peer
Network in which each node can share its files with all the other nodes. Each node has its own data and there is no central server
Thin client
Device that needs access to the internet for it to work + depends a more powerful computer for processing
Thin client
Device that needs access to the internet for it work + depends on a more powerful computer for processing
Thick client
Device which can work both offline and online + is able to do some processing even if not connected to a network/internet
Bus network topology
Network using single central cable in which all devices are connected to this cable so data can only travel in one direction and only one device is allowed to transmit at a time
Packet
Message/data sent over a network from node to node (includes the address of the node sending the packet, address of recipient and actual data)
Star network topology
Network that uses a central hub/switch with all devices connected to it so that all data packets are directed through the hub/switch
Mesh network topology
Interlinked computers/devices which use routing logic so data packets are sent from sending stations to receiving stations via the shortest route
Hybrid network
Network made up of a combination of other network topologies
Cloud storage
Method of data storage where data is stored on off-site servers
Data redundancy
Situation in which the same data is stored on several devices in case of maintenance or repair
Wi-Fi
Wireless connectivity that uses radio waves, microwaves. Implements IEEE 802.11 protocols
Bluetooth
Wireless connectivity that uses radio waves in the 2.45GHz frequency band
Spread spectrum frequency hopping
Method of transmitting radio signals in which a device picks one of 79 channels at random, if in use it randomly picks another. Has a range up to 100 metres
WPAN
Wireless Personal Area Network
Local wireless network which connects devices in very close proximity (laptop, phone, home devices etc)
Twisted pair cable
Cable in which 2 wires of a single circuit are twisted together, several of these pairs make up a single cable, most common cable type in LANs. Lowest data transfer rate and suffers from external interference but is the cheapest option
Coaxial cable
Cable made up of central copper core, insulation, copper mesh and outer insulation. Most commonly used in MANs + by television companies. Higher cost but better data transfer rate (80x better capacity than twisted pair) and less affected by external interference. Greatest signal attenuation. Best anti-jamming capabilities
Fibre optic cable
Cable made up of glass fibre wires which uses pulses of light rather than electricity to transmit data. Most commonly used over long distances. Best data transfer rate, smallest signal attenuation, highest cost. 26 000 times the transmission capacity of twisted pair cables
Gateway
Device that connects LANs which use different protocols
Repeater
Device used to boost a signal on both wired(analogue/copper and digital/fibre optic) and wireless networks (prevents dead spots in WiFi zone and are termed non-logical devices because they boost ALL detected signals)
Repeating Hubs
Network devices which are a hybrid of hub and repeater unit
Bridge
Device that connect LANs using the same protocols can be wired or wireless
Softmodem
Software modem
Software based modem that uses minimal hardware
NIC
Network Interface Card
Allow devices to connect to the internet (associated with a MAC address set at the factory)
WNIC
Wireless Network Interface Cards
Ethernet
Protocol IEEE.802.3 used by many wired LANs
Conflict
Situation in which 2 devices have the same IP address
Broadcast
Communication where pieces of data are sent from sender to receiver
Collision
Situation where 2 messages/data from different sources are trying to transmit along the same data channel
CSMA/CD
Carrier Sense Multiple Access with Collision Detection
Method used to detect collisions and resolve the issue
When a frame is sent it causes a voltage change on the Ethernet cable, when a collision is detected a node stops transmitting a frame and transmits a ‘jam’ signal and waits for a random time interval before resending the frame
Bit streaming
Contiguous sequence of digital bits sent over a network/internet
Buffering
Store which temporarily holds data
Bit rate
Number of buts per second that can be transmitted over a network. Measure of the data transfer rate over a digital telecoms network
On demand (bit streaming)
System that allows users to stream video or music files from a central server as + when required without having to save the files on their own computer/tablet/phone
Real time (bit streaming)
System in which an event is captured by camera + microphone connected to a computer and sent to a server where the data is encoded. User can access data live
WAN vs the internet
Internet is a vast number of decentralised networks+computers which have a common point of access so any one with internet access can connect to computers on these networks
WAN required passwords or user IDs to access it
Benefits of networking computers and devices (7)
Devices can be shared (reducing costs)
Licences to run software on networks are often far cheaper than for an equivalent no. Of stand alone computers
Users can share files and data
Access to reliable data that comes from a central source eg. file server
Data files can be backed up centrally at the end of each day
Users can communicate using email and instant messaging
A network manager can oversee the network and apply access rights to certain files/restrict access to external networks
Drawbacks of networking computers and devices (4)
Cabling + services are expensive
Managing a large network is complex and difficult
Breakdown of devices can affect the whole network
Malware + hacking can affect entire networks (firewalls help)
Hardware infrastructure of networked computers (5)
LAN cards
Routers
Switches
Wireless routers
Cabling
Software infrastructure of networked computers (3)
Operation + management of the network
Operation of firewalls
Security applications/utilities
Services of networked computers (4)
DSL (optic fibre)
Satellite communication channels
Wireless protocols
IP addressing
Categories of networks (2)
Public
Private
Private networks
Networks owned by a single company or organisation. Often LANs/intranets with restricted user access. Companies responsible for purchase of own equipment and software, maintenance of network + hiring and training of staff
Public networks
Networks Owned by a communications carrier company used by many orginisations, there are no specific password requirements but sub-networks may be under security management
Describe function of LANs
Consists of a number of computers + devices connected to hubs/switches, one of which is connected to a router and/or modem to allow the LAN to connect to the internet/become part of a WAN
Function of WAPs
Wireless access points
Connected to the wired network at fixed locations, commercial LANs (because of limited range) need several WAPs to permit uninterrupted wireless communications. Use spread spectrum technology(Wideband radio frequency) or infrared (short range+easily blocked)
Receives and transmits data between the WLAN and the wired network structure
How end users access the WLAN
Through wireless LAN adapters which are built into the devices/as a plug in module
Function of WANs (3)
Wide Area Networks
Used when computers/networks are situated far from each other. Formed by joining a number of LANs using a router or a modem.
Make use of public communications network or dedicated/leased lines (less expensive and more secure)
Consists of several end systems and intermediate systems
Guide to decide the size of a network (4)
PAN - 1m to 10m (home system)
LAN - 10m to 1000m
MAN - 1km to 100km
WAN - 100km to 1000+km
Types of networking models (2)
Client server
Peer to peer
Client server models (10)
Uses separate dedicated servers + specific client workstations
Users able to access most of the files stored on dedicated servers
Server dictates which users are able to access which files
Allows installation of software onto a clients computer
Uses central security databases (control access to shared resources)
Logged in users will only have access to resources assigned to them by the network administrator
Can be as large as you want and easy to scale up
Central server looks after storing, delivery and sending of emails
Offers the most stable system (nightly backup restores deleted resources)
Can become bottlenecked if there are several client requests simultaneously
Most important part of client-server vs peer-to-peer model
Client server: sharing of data
Peerto-peer: connectivity
Responsibilities of a file server in client-server model (3)
Central storage + management of files
Allowing users to share info without the need for offline devices (memory sticks)
Allowing any computer to be configured as the host machine and act as the file server
Why would you use a client-server model (4)
Company/user has a large user-base
Access to network needs to be properly controlled
Need for good network security
Company requires data to be free from accidental loss (needs to be backed up at a central location)
Example of client server model
Example of peer-to-peer model
Amazon
Small business where there is frequent user interaction
What each node joining the peer-to-peer network allows (5)
Provision of services to all other network users
Other users on the network to simply access data from another node
Communication with peers connected to the network
Peers to be both consumers and suppliers (client server keeps them separate)
Peers to participate as equals on the network
Function of peer-to-peer
Does not have a central server(thus meaning there is no requirement to authenticate users), each of the nodes on the network can share its files with all the other nodes and each of the nodes will have its own data.
Used where no more than 10 nodes are required (leads to performance + management issues)
Security of peer-to-peer
Little since there is no central security system, so it is impossible to know who is authorised to share certain data. Users can create their own network node share point as the only real security aspect, but there are no real authentication procedures
When would peer-to-peer be used (3)
Network of users is fairly small
No need for robust security
Require workstation-based applications rather than server-based
What client server model offers (2)
Thin clients and thick clients
Pros of thick clients (2)
More robust (device can carry out processing even when not connected to server)
Clients have more control (can store their own programs + data/files
Cons of thick clients (3)
Less secure (relies on clients to keep their data secure)
Each client needs to update data+software individually
Data integrity issues, many clients access the same data leading to inconsistencies
Pros of thin clients (3)
Less expensive to expand
All devices linked to a server (data updates + new software installation done centrally)
Server can offer protection against hacking + malware
Cons of thin clients (2)
High reliance on the server (if it goes down/there is a link break devices cannot work)
Start up costs are generally higher than for thick clients
Ways to connect computers to make complex networks (4)
Bus networks
Star networks
Mesh networks
Hybrid networks
Thin client vs thick clients software (4 for each)
Always reliefs on connection to remote server/computer - can run some features when not connected
Requires few local resources (eg. SSD,RAM) - Relies heavily on local resources
Relies on a fast, stable network connection - more tolerant of a slow network connection
Data stored on a remote server/computer - can store data on local resources (HDD/SDD)
Disadvantages of bus network topology (3)
If main cable fails the whole network goes down
The performance of the network deteriorates under heavy loading
Network is not secure since each packet passes through every node
Advantages of bus network topology (2)
Network continues to function if a node fails
Easy to increase size of the network by adding additional nodes
Suitability of bus networks
Situations with a small number of devices with light traffic occurring (small company/office environment)
Function of bus networks
PEER TO PEER
Uses single cable to connect all computers + devices. Data can only travel in 1 direction so if data is being sent between devices other devices cannot. Requires terminators at each end to prevent signal reflection. Each node looks at each packet, determines if the address of recipient matches the node address, if not it is ignored.
Disadvantages of a star network (2)
High installation costs
Of central hub/switch fails, whole network goes down
Advantages of star network (4)
Reduced data collisions
More secure network (security methods can be applied to central node, packets only travel to nodes with correct address)
Easy to improve by installing an upgraded hub
If one of the connections is broken it only affects one of the nodes
Suitability of star networks
Evolving networks where devices are frequently added or removed/apllication where there is heavy data traffic
Function of star networks
CLIENT SERVER
Each device is connected to the central hub/switch, through with data is directed. Each device has its own dedicated connection and any type of network cable can be used.
If hub: packets sent to every device on network (accepted/ignored depending on address)
If switch: packets only sent to nodes where address matches the recipient address in the packet
Examples of mesh network topology (4)
Internet and WANs/MANs
Medical monitoring of patients in a hospital
Electronics interconnectivity
Modern vehicles
Function of mesh networks
PEER TO PEER
2 types: routing and flooding
Routing: works by giving nodes routing logic (act as routers) so data is directed via the shortest route to its destination and can be rerouted
Flooding: sends data via all nodes using no routing logic (leads to unnecessary loading on the network)
Disadvantages of mesh networks (2)
Large amount of cabling needed (expensive+time consuming)
Set up + maintenance is difficult + complex
Advantages of mesh networks (4)
Easy to identify where faults on the network have occurred
Broken links do not affect other nodules
Good privacy + security (packets travel along dedicated routes)
Relatively easy to expand
Disadvantage of hybrid networks
Can be very complex to install, configure and maintain
Advantages of hybrid networks (3)
Can handle large volumes of traffic
Easy to identify where a network fault has occurred
Very well suited to the creation of larger networks
Systems of cloud computing (3)
Public
Private
Hybrid
Public cloud
Storage environment where the customers/client and cloud storage provider are different companies
Private cloud
Storage provided by a dedicated environment behind a company firewall. Customer/client and cloud storage provider are integrated + operate as a single entity
Hybrid cloud
Combination of private and public clouds, some data resides in the private cloud, less sensitive/less commercial data can be accessed from a public cloud storage provider
Pros of cloud storage (5)
Files can be accessed anytime from any device anywhere is internet access is available
No need to carry an external storage device/use the same computer to store information
Provides a remote back-up of data (aids data loss and disaster recovery)
Recovers data if a customer/client has a hard disk/back-up device failure
Offers almost unlimited storage capacity
Cons of cloud storage (4)
Problems accessing/downloading files with a slow/unstable internet connection
Costs high if large storage capacity is required
Expensive to pay for high down/upload data transfer limits with internet service provider
Potential failure of cloud storage company (loss of all back-up data)
Data security concerns with cloud storage (3)
Physical security by the building where the data is housed
Service providers resistance to natural disasters/powercuts
Safeguards regarding personnel who work for the cloud service company
Areas covered by cloud (5)
Storage
Databases
Networking
Software
Analytical services using the internet
Cloud software
Cloud software
Allows software applications to be delivered on demand. The provider will manage and maintain the applications for a monthly fee. The software is fully tested and does not need to reside on the users device, but the user can still use the software if the internet is lost, the data will then be stored in the local device and uploaded when the connection returns
When is Bluetooth useful (3)
Transferring data between 2 devices which are less than 30 metres apart
The speed of data transmission is not critical
Using low bandwidth applications
Bandwidth of radio waves, microwaves and infrared
Infrared>microwaves>radio waves
Penetration of radio waves, microwaves and infrared
Radio waves>microwaves>infrared
Attenuation of radio waves, microwaves and infrared
Radio>microwaves>infrared
Penetration
Ability of the electromagnetic radiation to pass through different media
Attenuation
Reduction in amplitude of a signal (infrared is low because it can be affected by rain)
Satellite technology
Curvature of the earth prevents electromagnetic waves from carrying signals globally, so signals are beamed from antenna A to a satellite orbiting earth, the signal is then boosted by the satellite and is beamed back to earth and picked up by antenna B
Communication between satellite and antennae
Carried out by radio waves / micro frequencies. Different bands are used to prevent signal interference + allow networks across the earth to communicate
Types of cables in wired networks (3)
Twisted pair cables
Coaxial cables
Fibre optic cables
Types of twisted pair cables (2)
Shielded (commercial, contains thin metal foil jacket to cancel out external interference)
Unshielded (residential)
Types of fibre-optic cables (2)
-Single mode (single mode light source, smaller central core, less reflection along the cable so faster and further data travel so best for telecommunications and CATV)
-Multi-mode (multi-mode light source, construction causes higher light reflections in core, so work best over short distances, best for LAN)
Pros of bitcoin streaming (5)
No need to wait for a whole video/music file to download before watching/listening
No need to store large files on your device
Allows video + music files to be played on demand
No need for any specialist hardware
Affords piracy protection (more difficult to copy streamed files)
Cons of bit-streaming (5)
Can’t stream video/music files if broadband connection is lost
Video/music files paused streaming to catch up (insufficient buffer capacity/slow broadband connection)
Uses a lot of bandwidth
Security risks of downloading from the internet
Copyright issues
How on demand bit streaming works (5)
Digital files stored on server converted to a bit streaming format
Link to encoded to video/music file is placed on the web server to be downloaded
User clicks on the link and the file is downloaded in a contiguous bit stream
Streamed video/music is broadcast to the user as and when required
Possible to pause rewind and fast forward if required
How real time bit streaming works
Event is captured by camera and microphone and is sent to a computer
Video signal is converted to a streaming media file
Encoded file is uploaded from the computer to the dedicated video streaming server
Server sends the encoded live video to the users device
Not possible to pause, rewind or fast forward since it is live
Drawbacks of repeating hubs (repeaters) (2)
Only have 1 collision domain, so need jamming signals to manage collisions, but reduces network performance since it involves repeated broadcasts
Devices are referred to as unmanaged since they are unable to manage delivery paths + security in the network
Role of routers (5)
Restricts broadcasts to a LAN
Act as a default gateway
Can perform protocol translation (lets wired communicate with WiFi by protocol conversion)
Can move data between networks
Can calculate best route to destination address
Internet
Massive network of networks, made up of computers and other electronic devices; uses TCP/Ip communication protocols
WWW
World Wide Web
Collection of multimedia web-pages stored on a website which uses the internet to access information from servers and other computers. Http(s) protocols are written using HTML, URLs specify the location of all web pages, web resources are accessed by web browsers.
HTML
Hypertext Mark-up Language
Used to design web-pages + to write http(s) protocols
URL
Uniform Resource Locator
Specifies location of a web page
Web browser
Software that connects to DNS to locate IP addresses; interprets web pages sent to a users computer so that documents and multimedia can be read or watched/listened to
ISP
Internet Service provider
Company which allows a user to connect to the internet, usually charge a monthly fee for the service they provide
PSTN
Public Switched Telephone Network
Network used by traditional telephones when making calls/sending faxes
VoIP
Converts voice and webcam images into digital packages to be sent over the internet
Carries out file compression to reduce the amount of data being transmitted
IP
Internet protocol
Uses IPv4 or IPv6 to give addresses to devices connected to the Internet
IPv4
IP address format which uses 32 bits giving 2*32 possible addresses
32 bits are split into 4 bits of 8 (range of 0-255)
CIDR
Classless internet-domain routing
Increases IPv4 flexibility by adding a suffix to the IP address eg. 200.21.100.6/18
IPv6
Newer IP address format which uses 128 bits (hex)
Zero compression
Way of reducing the length of an IPv6 address by replacing groups of zeroes by a double colon (::); can only be applied once to avoid ambiguity
Sub-netting
Practice of dividing networks into 2 or more sub-networks, reduces network traffic and hides the complexity of the overall network. Splits the HostID
Private IP address
IP address reserved for internal network use behind a router
Public IP address
IP address allocated by the user’s ISP to identify the location of their device on the Internet
DNS
Domain Name Server/System
Gives domain names for Internet hosts and is a system for finding IP addresses of a domain name
Eliminates the need for the user to memorise IP addresses
JavaScript
Object-oriented programming language used mainly on the web to enhance HTML pages
PHP
Hypertext processor
HTML embedded scripting language used to write web-pages
Differences between the internet and the worldwide web (8)
Internet:
-massive network of networks made up of various electronic devices
-stands for interconnected network
-makes use of transmission control protocol(TCP)/Internet protocols (IP)
Www:
-collection of multimedia web pages and other documents stored on websites
-http(s) protocols written using HTML
-URLs specify location of all web pages
-www uses internet to access information from servers and other computers
Requirements for connecting to the internet (5)
Device
Telephone line/mobile phone network connection (may be wireless)
Router
ISP
Web browser
What happens when using the internet to make a phone call
Users voice is converted to digital packages using Voice over Internet Protocol (VoIP)
Phone calls using PSTN
Public switched telephone network
Uses a standard telephone connected to a phone line which is always open and not terminated until the receivers are replaced by both parties. It even remains active during power cuts as they have their own power source. Modern digitised systems use fibre optic cables meanwhile existing phone lines use circuit switching
Phone calls using the Internet
Use either an Internet phone or microphone and speakers (and webcam for video calls)
Connection is only live while data is being transmitted
VoIP converts sound to digital packages which can be sent over the internet using packet switching, data is routed through thousands of possible pathways. The data is split into packages with each packet containing the sender and receivers address and order number. The sending computer sends data to router which sends packets to another router and so on until they arrive and are reassembled
Phone calls using cellular networks and satellites
Done by mobile phones which act as the ISPs since they contain communication software which allows the, to access the telephone network and make an internet connection
Satellites are used for network communications that cover large distances, due to the curve of the earth, the higher the satellite orbit the more coverage it can give
GEO
Geostationary orbit
Provides long distance telephone and computer network communications
35800 km
24 hour orbital period
GEO
Geostationary orbit
35800 km
24 hours
MEO
Medium Earth Orbit
GPS systems
5000-12000km
2-12 hour orbital period
LEO
Low Earth Orbit
Mobile phone networks
500-1200km
80 minutes-2 hour orbital period
Advantages of satellites
Always give complete coverage
Don’t suffer from signal attenuation to the same extent as underground/sea cables
Easier to isolate and resolve faults that undersea cables
Operation of broadband routers
Sit behind a firewall which protects the computers on the network.
Main function is to transmit the Internet and transmission protocols between 2 networks and allow private networks to be connected. Inspects data package sent to it, sends the packet to the appropriate switch (inspect IP) from which it will be delivered using the MAC address
Routers features (4)
Forward packets of data from one network to another
Route traffic between networks
Join LANs to form WANs or connect LANs to the internet
Offer additional features such as dynamic routing (ability to forward data by different routes)
WNIC modes (2)
Infrastructure mode - uses WAP (and hub/switch) to transfer all the data, all wireless devices must use the same security and authentication techniques
Ad hoc mode - does not have access to WAPs, possible for devices to interface with each other directly
Parts of a network using Ethernet (3)
Node (any device on the LAN)
Medium (path used by LAN devices such as Ethernet cable)
Frame (data is transmitted in frames made up of source and destination address (often MAC))
What public IP addresses are used by (3)
DNS servers
Network routers
Directly-controlled computers
Web browsers
Software that allow users to access using URLs and display web pages on their screens by interpreting HTML sent from websites and displaying the results.
Web browsers
Software that allow users to access using URLs and display web pages on their screens by interpreting HTML sent from websites and displaying the results.
Format of URL
protocol://website address/path/filename
Protocol is usually http/https
Content of website address (4)
Domain host (www)
Domain name (name of website)
Domain type (.com, .org etc.)
Country code (.uk, .za etc.)
DNS process (5)
-User opens browser, types in URL and the browser asks the DNS server(1) for the IP address of the website
-DNS server(1) can’t find it in its database or it’s cache and sends request to DNS server(2)
-DNS server(2) finds the URL and can map it to an IP address which is then sent back to the DNS server(1) which puts the IP address and associated URL into its cache/database
-IP address is then sent back to the user’s computer
-Computer sets up a communication with the server and downloads required pages, the browser interprets HTML and displays the information on the Users screen
Network class A
Give IPv4 range, no. of netID bits, no. of hostID bits, types of network
0.0.0.0 to 127.255.255.255
8
24
Very large
Network class B
Give IPv4 range, no. of netID bits, no. of hostID bits, types of network
128.0.0.0 to 191.255.255.255
16
16
Medium size
Network class D
Give IPv4 range, no. of netID bits, no. of hostID bits, types of network
-
Multi-cast
Network class E
Give IPv4 range, no. of netID bits, no. of hostID bits, types of network
-
Experimental
Network class C
Give IPv4 range, no. of netID bits, no. of hostID bits, types of network
192.0.0.0 to 223.255.255.255
24
8
Small networks
Benefits of IPv6 (4)
No need for NATs (Network Address Translations)
Removes risk of private IP address collisions
Has built in authentication
Allows for more efficient routing
