1.3 Flashcards
What are the advantages of networking?
- Share files
- Share peripherals
- Access files from any computer on the network
- Servers control security, software updates and data backup
- Communication with others
What are the characteristics of a local area network (LAN)?
- Covers a small geographical area
- Hardware owned by organisation using it
- Wired with UTP cable, fibre optic or wireless with Wi-Fi
What are the characteristics of a wide area network (WAN)?
- Covers a larger geographical area
- Infrastructure between LANs leased from telecommunication companies who own and manage it
- Connected with telephone lines, fibre optic cables, satellite links
What are the disadvantages of networking?
- 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
What are the factors that affect the performance of a network?
- Bandwidth
- Number of users
- Type of transmission media used
- Error rate
- Latency
- Interference
How does the number of users on a network impact its performance?
- Causes network to slow down if there is insufficient bandwidth for the data
What does bandwidth mean?
- Amount of data that can be sent and received successfully in a given time
- Measured in bits per second
What types of transmission media have a higher bandwidth?
- Wired bandwidth > wireless
- Fibre optic cables bandwidth > copper cable
- Due to less interference
What does interference mean?
- Signals are slowed down due to other factors
- e.g. physical factors: a wall
- e.g. the interaction of signals from different devices
- e.g. appliances such as microwaves may emit signals that interfere with signals sent out by routers
What does error rate mean?
- Number of errors that occur while data is transferred
- The higher the error rate, the more frequent data must be resent before arriving correctly
What affects signal quality?
- Wireless: range, environmental factors
- Wired: grade of material, length of cable
What does latency mean?
- Delay from transmitting data to receiving it
- Caused by bottlenecks in the network infrastructure
(e.g. hardware operates at different speeds thus unable to direct traffic effectively)
What is the role of a server in a client-server network?
- Controls access and security to a shared file store
- Manages Internet access
- Manages printing jobs
- Provides email services
- Runs data backup
What is the role of a client in a client-server network?
- Makes requests to the server for data
What is the role of a peer in a peer-to-peer network?
- All peers are equal
- Serve their own files to each other
- Usually have own printers
- Responsible for own security and backup
What is a stand-alone computer?
- A single computing device not connected to any other device on a network
What are the advantages of a client-server network?
- Easier to manage security
- Easier to backup all shared data
- Easier to install software updates to all computers
What are the disadvantages of a client-server network?
- Expensive to set up and maintain
- Requires IT specialists
- Server is a single point of failure
- Users lose access if server fails
What are the advantages of peer-to-peer networks?
- Easy to maintain
- No special staff required
- Not dependent on a single computer
- Cheaper
- No expensive hardware required
What are the disadvantage of peer-to-peer networks?
- Less secure
- Need to manage own backups
- Difficult to maintain well ordered file store
What is a network interface card (NIC)?
- A hardware component that allows a device to connect to a wired/wireless network
- Has a unique MAC address that allows it to be identified on a LAN
What is a wireless access point (WAP)?
- Allows wireless-enabled devices to connect to the network without cables
- Convenient
- Less bandwidth than wired
- Security is a concern
What is a switch?
- Sends data between computers on a LAN
- Uses MAC address to send data to its destination device
- Segments the network by forwarding traffic to the correct device
What is a router?
- Hardware used to connect networks
- Sends data between networks
- A LAN is required to network a WAN
- Uses IP addresses on a device to route traffic to other routers
What is transmission media?
- The channel used to transfer data over the network
- Either through cables or radio waves (wired or wireless)
What is a copper cable (UTP)?
- Creates a wired network
- One cable responsible for sending data, one responsible for receiving data
- Known as Ethernet cables
- Cheap and flexible
What are fibre optic cables?
- Uses light to transmit data
- Covers a larger range
- Higher bandwidth and has less interference than copper
- Expensive (but still better)
What is the internet?
- WAN
- Collection of interconnected computer networks spanning the world
What is the world wide web (WWW)?
- Service used on the internet
- Allows users to interact with the internet and share files across the internet
What is hosting?
- Websites/files/emails/videos are stored on dedicated host servers
- Can be accessed from any connected devices via Internet
- Hosts provide 24/7 access
- Allows access for multiple users
- Strong protection against hackers
- If host server goes down, your website goes down too
- Need an IP address that does not change
What is a web server?
- Where data for websites are stored
- Responsible for managing requests from clients
What is the domain name service?
- DNS consists of multiple domain name servers
- Each website is hosted on a web server
- Each website has an IP address
- When a user types in something into the search engine, 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 web server
- Web server processes request for the website
- Web server 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
What are the benefits of the DNS?
- Easier for human to remember a name of a website 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.
What is the cloud?
- Remote servers that store data that can be accessed over the internet
What are the advantages of the cloud?
- Access anytime
- Access anywhere
- Access from any device
- Large storage capacity
- Automatic backup
- Easy online collaboration
- High security
What are the disadvantages of the cloud?
- Requires an internet connection to access applications and files
- Data easier to hack when stored online (not possible to guarantee data security)
- Limited to small amount of free storage space before having to pay for further storage
- Entrusting a third-party company that could access your data
What is a star network topology?
- 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
What is a mesh network topology?
- Every device is connected to every device
- If a connection breaks, traffic can be routed via another route (resilient to faults)
- Huge cost due to a lot of cabling and switch hardware required
What is a partial network topology?
- 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
How is data transmitted via an ethernet connection?
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
What is Wi-Fi?
- A wireless connection to a network
- Requires a WAP or a router
- Data is sent on a specific frequency (called a channel)
What are the advantages of Wi-Fi?
- Users can move freely
- Easier to set up, cheaper (no cabling)
- Convenient
- Can handle larger number of users
What are the disadvantages of Wi-Fi (compared to wired connections)?
- Lower bandwidth
- Suffers from interference
- Less secure
What is bluetooth?
- Ideal for connecting personal devices
- Very short range
- Very low power consumption compared to Wi-Fi
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
- Data cannot be understood if intercepted
- Only the intended recipient can decode the data using a ‘master key’
What is the handshaking protocol?
- Ensures receiver has a valid master key before the transmission begins
Give some examples of protocols used for wireless encryption
WEP, WPA, WPA2
What are MAC addresses?
- Media access control address
- Unique identifier assigned to a NIC
- Identifies devices on a LAN
- Each device has a fixed address
What is the MAC address format?
- 48 bits per address
- 6 pairs of hexadecimals
- Separated by dashes or colons
What is an IP address?
- Unique string of numbers that identifies each device connected to the internet
- Allows data to be directed around the internet from senders to the correct receivers
What is the IPv4 address format?
- 32 bits per address
- 4 groups of decimal numbers
- Each number is in the range 0-255
- Separated by periods
- e.g. 172.16.254.1
What is the IPv6 address format?
- 128 bits per address
- 8 groups of 4 hexadecimal digits
- Each group has 4 hex values
- Separated by colons
- e.g. 0123:4567:89ab:cdef:01234:3456:abcd:4321
What are 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
Give some examples of standards
- ASCII/UNICODE
- HTML
- PDF, PNG, MP3
What is a protocol?
- Set of rules that allows two devices to communicate
What is TCP/IP?
- Transmission Control Protocol
- Internet Protocol
- Transmits data across a network
What is HTTP?
- Hyper Text Transfer Protocol
- Defines the rules to be followed by a web browser/server when requesting/supplying information
What is HTTPS?
- Hyper Text Transfer Protocol Secure
- Authentication and encryption of data when requesting/delivering web pages
- Used when sensitive data needs to be transferred
What is FTP?
- File Transfer Protocol
- Used to send files between computers (normally on a WAN)
What is POP?
- Post Office Protocol
- Retrieves mail from a mail server
- Removes it from the server and transfers it to your device
What is SMTP?
- Simple Mail Transfer Protocol
- Sends email to an email server
Wha is IMAP?
- Internet Message Access Protocol
- Retrieves a copy of an email from a mail server
- Allows synchronicity between devices
What are layers?
- Division of network functionality
Why do protocols have layers?
- Dividing complex tasks of networking into smaller and simpler tasks that work with each other
- Each layer is independent (can be changed without affecting others)
- Each layer has its own responsibility
- Each layer can be developed by different manufacturer
Describe a difference between a switch and a router?
- Switch is used to transmit data on a LAN
- Router is used to transmit data on a WAN
What does Mbps stand for?
Megabits per second
Explain the difference between IPv4 and IPv6 and why IPv6 is necessary
- 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)
- 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
