(9) Coms & Network Flashcards
What is serial transmission?
Serial - Single bits are sent along a single wire one after the other at a time
What are the advantages and disadvantages of serial transmission?
+Reliable over long distance
+Reduced cost as less wires are required
+Reduced chance of skew
What is parallel transmission?
Parallel - Single bits are sent along several wires simultaneously
What are the advantages and disadvantages of parallel transmission?
+Ideal for short distances
+
- Close wires can cause a corruption
- Prone to skew (Timing issues)
What is synchronous data transmission with an example?
When data is transferred at a regular intervals synchronised by a clock pulse
E.g Chats and video
What is asynchronous data transmission with an example?
When data is sent separately and as soon as they are ready
E.g keyboard and mouse
Synchronous V Asynchronous
- Asynchronous is slower due to the extra bits and gaps
- Asynchronous can transmit when ready as it doesn’t need to wait on a clock pulse
- Synchronous may have to wait for a clock pulse before it can be sent
- Synchronous requires a synchronised clock between devices which can be difficult
What is the purpose of start and stop bits in asynchronous transmissions?
They are a bit used to indicate the start and the end of a set of data in asynchronous data transmission
What is baud rate?
The number of times a signal in a communication changes state
What is bit rate?
The number of bits transferred between devices per second
What is bandwidth?
A measure of maximum capacity of a given transmission channel
What is latency?
The time delay between when a transmission data is first sent to when its delivered at its destination
What is a protocol?
A set of rules that govern communication between devices
What’s the relationship between bit rate and bandwidth?
The relationship between bandwidth and bit rate is directly proportional: the greater the amount of data that can be transmitted over a channel, the more bits can be transmitted per second.
What is a bus topology?
All computers are connected to a single wire with terminals at each end
What is a star topology?
When computers are centred around a node (switch) each connected with their own cable
What are the advantages and disadvantages of a bus topology?
+Inexpensive as it requires less cables
- Reliant on main cable
- Performance degrades with increased traffic
- Low security as all computers on the networks can see data transmissions
What are the advantages and disadvantages of a star topology?
+If one cable fails it only affects that one computer
+Performance stays consistent as more computers are added
- Cost as more cables
- If the switch breaks down the whole network goes down
What is peer to peer networking and when they might be used?
No central server. All clients have equal responsibility so each computer can act as both a client or a server
E.g small businesses, home networks
What is client server networking and when they might be used?
When a device (client) requests access to resources and services from a central server
Eg schools - students as clients
What are the advantages and disadvantages of peer to peer networking?
+If a node goes down only the data on that node is lost
+Easily share files
What are the advantages and disadvantages of a client-server networking?
+Increased security
+Backups can be done for all clients
+Data can be shared
- Expensive to install and manage
- Professional IT staff are required to maintain the servers
What is the purpose of Wi-Fi?
Allows you to transfer data between devices without cables components being required for a wireless network
What components are required for wireless networking?
Each device must have a wireless network interface card (NIC) to be able to connect to a wireless access point (WAP). The WAP allows devices to connect to a wired network (internet)
What is the difference between thin and thick clients?
Thin clients - Majority of the processing and storage is done on the server
Thick clients - Majority of the processing and storage is done on the client
What are the advantages and disadvantages of thin clients?
+Software updates can be done once on a server and automatically end up on every client
+Easy to set up and maintain e.g. adding a new terminal to the network
+Much more secure as all data is stored in one place
- Very reliant on the central server
- Can be expensive as it requires a powerful and reliable central server
- High demand on bandwidth
What are the advantages and disadvantages of thick clients?
+Reliable
+Can operate without a continuous connection to the server
+Preferred when running heavy duty software
- Expensive as each client may need a higher specification (better computer)
- Time consuming when installing new software
What is the transmission control protocol/ internet protocol (TCP/ IP) and the 4 layers?
It’s 4 layers required to allow data to be transmitted across the internet
Application, Transport, Network, Link
What is the application layer in the TCP/ IP?
Selects the appropriate protocol for communication
E.g FTP, HTTP/S, POP3
What is the transport layer in the TCP/ IP?
Creates an end to end connection and splits the data into packets and numbers them
What is the network layer in the TCP/ IP?
Adds the source and destination IP address and routers use the IPs to route the packets to the destination
What is the link layer in the TCP/ IP?
The physical connection between the nodes and adds the source and destination MAC addresses
What are MAC addresses and where is it used in the TCP/IP?
A unique code that’s physically hardcoded on every NIC during manufacturing.
Used in the link layer of the TCP/IP
What is a firewall?
Hardware or software for protecting against unauthorised access to a network
What is a proxy server?
Inspects all packets coming in and out of a network while hiding the network addresses of the source from the recipient
What is packet filtering?
Examining the contents of packets on a network and rejecting them if they don’t meet certain requirements
What is stateful inspection?
Examining the contents of packets on a network and rejecting them if they don’t form part of a recognised communication
What is a worm?
Malware that can replicate itself and spreads around a computer
-
What is a trojan?
Malware that is hidden within another file on your computer
What is a virus?
Malware where the program attaches itself to another file in order to invest a computer
What are the vulnerabilities that malware take advantage of?
- Human error
- System bugs
- People turning off their firewalls or failing to update their virus protection
What is subnet masking?
A method of dividing a network into multiple smaller networks
What are well-known ports and what are they used for?
They are common ports that are used to launch various applications related to their protocols
What are client ports and what are they used for?
A port that is temporarily assigned for the duration of a connection
Establishes the connection between the client and server application*****
What is the use of the FTP protocol and its number?
File Transfer Protocol
20 - A protocol for handling file uploads and downloads
What is the use of the HTTP protocol and its number?
Hypertext Transfer Protocol
80 - A protocol used for exchanging web-pages
What is the use of the HTTPS protocol and its number? What is the acronym?
Hypertext Transfer Protocol Secure
443 - A protocol used for exchanging secure web-pages
What is the use of the POP3 protocol and its number?
Post office Protocol
110 - A protocol for receiving emails
What is the use of the SMTP protocol and its number?
Simple Mail Transfer Protocol
25 - A protocol for sending emails
What is the use of the SSH protocol and its number? What is acronym?
Secure Shell
22 - A protocol that provides secure remote access to a server
How is SSH used for remote management?
- Client indicates the connection to the server
- Server sends public key
- Client and server agree communication rules
- User can now login remotely
What is the FTP Client?
A software application that works with the FTP protocol to allow users to easily interact with it instead of learning the appropriate commands to use
What does anonymous and non-anonymous access mean in regards to FTP servers?
Anonymous - FTP site/ server doesn’t require a login information
Non-anonymous - FTP site/ server does require a login information
What are the two types of IP addresses?
v4 and v6
What is IPv6 and why was it introduced?
The internet was was massively growing so IPv4 (32 bits) was no longer enough, soIPv6 (128 bits) was introduced to allow for a greater range of custom IP addresses
What is the difference between routable (public) and non-routable (private) IP addresses?
Routable
- Can be connected directly to the internet
- It is globally unique
Non-routable IP
- Can be accessed directly from the internet
- Many devices may have the same address
- More secure as its not directly connected to the internet
What is the purpose and function of the DHCP system?
A set a rules for allocating locally unique IP addresses to devices as they connect to a network
What is NAT and why is it used?
Used to match up the private IP addresses with the public ones
What layer in the TCP/ IP stack does the router operate?
Network
What is a router and where and why is it used?**
A device that connects two or more devices together and forwards data packets between networks
Used for:
Internet access
Where:
Homes
Offices
What is the role of packet switching?
A method of sending data across a network to reach a destination
What is a gateway and where and why is it used?
A node that sits between different networks and converts data from one protocol to another
Used to:
Connect two different company networks together
Provide a house user access to the internet
What are the main components of a data packet and what does each part contain?
Header - Source and destination IP and Mac address, Packet and sequence number
Payload - The actual data itself
Trailer - A checksum to ensure that the data has been received correctly
What is a uniform resource locator (URL)?
A method of identifying the location of resources on the internet
What are the 5 components of a URL?
Https://stephanbarnes.com/alevel/computing/flashcards
Host, FQDN, Domain Name, Location, Resource
What is a fully qualified domain name (FQDN)?
The complete domain name that identifies a specific host on the internet. It includes the host server name along with the domain name
Eg www.stephanbarnes.com
What is an IP address?
A unique address that is assigned to a network device
What is a domain name?
Identifies the location of the the resource on the internet.
Identifies organisations or groups on the internet
How are domain names organised?
They are organised in a hierarchy
What is a node?
Any system or device connected to a network
What is the formula for bitrate?
Baud Rate * Number of Bits per Baud
What is the purpose of a Domain Name System (DNS)?
To link a fully qualifies domain name (FQDN) to an IP address
What is the service provided by internet registers and why are they needed?
Describe the structure of the internet
What is the purpose and function of the domain service and its relevance on the domain name server (DNS) system?
How is routing achieved across the internet?
Describe one situation when a DNS query will not be sent to a remote DNS server.
The local computer already has a copy of the IP address in a host file.
