1.3 Flashcards
Networking Advantages (5)
- Share files
- Share peripherals
- Access files from any computer on the network
- Servers control security, software updates and data backup
- Communication with others
LAN (3)
- Covers a small geographical area
- Hardware owned by organisation using it
- Wired with UTP cable, fibre optic or wireless with Wi-Fi
WAN (4)
- Covers a larger geographical area
- Connects LANs together
- Infrastructure between LANs leased from telecommunication companies (own and manage it)
- Connected with telephone lines, fibre optic cables, satellite links
Networking Disadvantages (4)
- Increased security risks to data
- Malware and viruses are able to spread very easily
- If server fails, computers connected to it may not work
- Computer may run slowly due lots of data travelling on the network
Factors that affect network performance (5)
- Bandwidth
- Number of users
- Transmission media
- Error rate
- Latency
Bandwidth
Amount of data that can be sent and received in a given time (how much rather than how fast) (measured in bit rate)
Number of Users
Causes network to slow down if there is insufficient bandwidth for the data
Transmission Media (2)
- Wired bandwidth > wireless
- Fibre optic cables bandwidth > copper cables
Error Rate (2)
- Less reliable connections = more error occur when data is transferred
- Must be resent until successful
Signal Quality (3)
- Wireless: range, environmental factors
- Grade of material
- Length of cable
Latency (2)
- Delay from transmitting data to receiving it
- Caused by bottlenecks in the network infrastructure
(e.g. hardware operates at different speeds)
Role of a server in a client-server model (5)
- Server controls access and security to a shared file store
- Manages Internet access
- Manages printing jobs
- Provides email services
- Runs data backup
- Client makes requests to the server for data
Role of a client in a client-server model
- Makes requests to the server for data
Role of a peer in a peer to peer model
- Peer: computer on a network
- All peers are equal, they share their own files to each other
- Usually have own printers
- Responsible for own security and backup
Advantages of Client-Server Model (3)
- Easier to manage security
- Easier to backup all shared data
- Easier to install software updates to all computers
Disadvantages of Client-Server Model (4)
- Expensive to set up and maintain
- Requires IT specialists
- Server is a single point of failure
- Users lose access if server fails
Advantages of Peer-to-Peer Model (5)
- Easy to maintain
- No special staff required
- Not dependent on a single computer
- Cheaper
- No expensive hardware required
Disadvantages of Peer-to-Peer model (3)
- Less secure
- Need to manage own backups
- Difficult to maintain well ordered file store
Network Interface Card (NIC) (2)
- Allows a device to connect to a wired/wireless network
- Uses a protocol to determine how connection should work
Wireless Access Point (WAP) (5)
- Allows wireless-enabled devices to connect to the network without cables
- Convenient
- Less bandwidth than wired
- Security is a concern
- Connection not as strong or reliable as wired
Switch (2)
- Sends data betweens computer on a LAN
- Uses NIC address on a device to route traffic to the correct location
Router (3)
- Sends data between networks
- Needed to connect a LAN to a WAN
- Uses the IP address to route traffic
Copper Cables (UTP) (2)
- Makes connections between computer and a switch
- Cheap and flexible
Fibre Optic Cables (2)
- Covers a longer distance (so WANs)
- Higher bandwidth and has less interference than copper
The Internet
- Most well known WAN
- Collection of interconnected networks spanning the world
WWW
- Service used on the internet
- Allows users to interact with the internet and share files across the internet
Hosting (4)
- Websites are stored on dedicated host servers
- Hosts provide 24/7 access to the website
- Allows access for multiple users and has greater security
- If host server goes down, your website goes down too
Web Server
- Where data for websites are stored
- Responsible for managing requests from clients
What is the Domain Name Server? (10)
- The website is hosted on a webserver
- The website has an IP address
- The browser sends URL to DNS
- URL has a corresponding IP
- DNS finds IP
- If DNS cannot find the IP it passes request to higher DNS, if not found returns error
- IP address sent back to browser
- Browser sends request to webserver
- Webserver processes request for the website
- Webserver sends webpage to the user
What helps the DNS resolver server carry out the process?
- Multiple domain name servers
- If the first DNS does not have the required information, it is passed onto the next DNS and so on
Advantages of the DNS (2)
- Easier for human to remember a name than a series of numbers
- If the IP address changes, the domain name does not have to
Describe how a DNS server is used to access a website (3)
- DNS servers have a database of domain names, which are constantly updated by other DNS servers
- When you request a website address, the DNS server looks up the address and translates it into an IP address
- If it does not have the address in its database, it passes it up the hierarchy to another DNS server until it is found. If it can’t, an error message is displayed.
The Cloud
Servers that store data and programs that can be accessed and used over the Internet
Advantages of the Cloud (6)
- Access anytime
- Access anywhere
- Access from any device
- Large storage capacity
- Automatic backup
- Easy online collaboration
Disadvantages of the Cloud (4)
- Requires an internet connection
- Easier to hack
- Limited to small amount of free storage space, have to pay
- Security, entrusting a third-party company that could access your data
Star Network Topology (6)
- Most popular wired network
- Based around a central switch
- All devices connect to central switch
- Switch makes sure traffic only goes to where it is intended
- If a single cable breaks, only that computer is affected
- Switch is a serious point of failure
Full Mesh Network Topology (3)
- Every device is connected to every device
- If a connection breaks, traffic can be routed via another route
- Huge cost due to a lot of cabling and switch hardware required
Partial Mesh Network Topology (3)
- Multiple routes exist between devices
- Not every device is not connected to every device
- Compromise solution that lowers the amount of hardware that is purchased
Ethernet
- Used for communication on a wired LAN
How is data transmitted via an ethernet connection? (5)
In frames:
- Bits used to synchronise transmission
- Start frame delimiter to signify start of data
- Sender and receiver MAC address
- Actual data
- Cyclic redundancy check to check for errors on frame
Advantages of Wi-Fi (8)
- Common standard for wireless networks
- Users can move freely
- Easier to set up, cheaper
- Convenient
- Can handle larger number of users
- Slower than wired networks
- Relies on signal strength
- Less secure
Bluetooth
- Another standard for wireless network
- Ideal for connecting personal devices
- Very short range
- Very low power consumption compared to Wi-Fi
What is required for data to be sent via Wi-Fi?
- Frequencies: used to transmit signals
- Channels: must be set the same for devices to connect
Why is wireless encryption needed?
- Wireless networks broadcast data, so in order for it to be secure, it must be encrypted
- Sensible precaution when handling personal data
How does wireless encryption work?
- Scrambling data into cipher text
- Using a ‘master key’
- Data is decrypted by the receiver using the same master key (not transmitted)
What is the handshaking protocol?
Ensures receiver has a valid master key before the transmission begins
Examples of protocols used for wireless encryption
WEP, WPA, WPA2
MAC addresses (3)
- Media access control address is a unique identifier assigned to a NIC
- It identifies devices on a LAN
- Each device has a fixed address
IP Address
- Used to route packets on a WAN
- Has two versions: IPv4 and IPv6
IPv4
- 32 bits
- Four numbers
- Each number is in the range 0-255
- Separated by periods
Routers (addresses?)
- Unique WAN facing IP
- Unique LAN facing IP
Is it possible for devices to have the same IP address?
- Yes!
- As long as they are on different LANs
IPv6
- 128 bits
- Written in 8 groups
- Each group has 4 hex values
- Separated by colons
Standards
A set of specifications for both hardware and software to be compatible
Why are standards needed?
- For manufacturers to create products and services that are compatible with each other
- Allows devices to successful interact
Example of Standards
- ASCII/UNICODE
- HTML
- PDF, PNG, MP3
Protocol
Set of rules that allows two devices to communicate
TCP
- Transmission Control Protocol
- Transmits data across a network from file server to a client
IP
- Internet Protocol
- Transmits webpage or data across a network from a server to a client
HTTP
- Hyper Text Transfer Protocol
- Defines the rules to be followed by a web browser/server when requesting/supplying information
HTTPS
- Hyper Text Transfer Protocol Secure
- Encryption of data when delivering web pages
- Used when sensitive data needs to be transferred
FTP
- File Transfer Protocol
- Used to send files between computers (normally on a WAN) from a server to a client
POP
- Post Office Protocol
- Retrieves mail from a mail server
- Removes it from the server and transfers it to your device
SMTP
- Simple Mail Transfer Protocol
- Sends email to an email server
IMAP
- Internet Message Access Protocol
- Retrieves a copy of an email from a mail server
- Allows synchronicity between devices
Layers
- Dividing complex tasks of networking into smaller and simpler tasks that work with each other
- Each hardware/software per layer has a defined responsibility
- Each layer provides a service to the layer above it
Advantages of Layering
- Reduces complexity of the problem into manageable sub-problems
- Devices can be manufactured to operate at a particular layer
- Products from different manufacturers work together
Describe a difference between a switch and a router PPQ
- Switch is used to transmit data on a LAN
- Router is used to transmit data on a WAN
What does Mbps stand for? PPQ
Megabits per second
Explain the difference between IPv4 and IPv6 and why IPv6 is necessary? PPQ
- IPv4 is 32 bits separated by periods
- IPv6 is 128 bits separated by colons
- It is necessary due to the increasing number of devices connected to networks
Sophia sends an email from her computer to her brother Fergus. Describe what happens to the email after this (3) PPQ
- Email sent to SMTP server
- Email routed over the internet: looks up Fergus’ email provider using the DNS to find the correct mail server, which is then forwarded
- Email is stored and retrieved by the email provider, storing the email until Fergus accesses his email. POP or IMAP is used to retrieve the email
