1.3.3 Networks Flashcards
What is a network?
Two or more computers connected together that can transmit data
What is a physical topology?
The physical layout of a network
What is a logical topology?
The way in which data flows around a network
What is a bus topology?
Network topology where all terminals are connected to a backbone cable
What is the advantage of a bus topology?
Cheaper to set up as no additional hardware
What are the two disadvantages of a bus topology?
If backbone cable fails, entire network disconnected
As traffic increases, performance decreases
What is a star topology?
Uses a central node to direct the flow of data
What can be used as a central node in a star topology?
A switch
A computer
What are used to identify devices on a star topology?
MAC addresses
What are the five advantages of a star topology?
Perfomance is consistent
If one cable fails, only that node is affected
Transmits data faster
Easy to add new nodes
No data collisons
What are the two disadvantages of a star topology?
Expensive
If central switch fails, network fails
What is a mesh topology?
Every node is connected to every other node
What are the three advantages of a mesh topology?
No cabling cost
As nodes increase, reliabiity and speed of network increases
Faster due to no central switch
What is the disadvantage of a mesh topology?
Difficult to maintain
What are protocols?
Set of rules defining how two devices communicate with each other
What is the Internet?
A network of networks
Allows computers across the world to communicate
What is the TCP/IP stack?
A stack of networking protocols that work together to pass packets during communication
Name the four layers of the TCP/IP stack.
Application
Transport
Network
Link
What happens at the application layer?
Specifies what protocol needs to be used for the application being sent
What happens at the transport layer?
End-to-end connection established between source and destination
Splits & labels data into packets
Requests retransmission of any lost packets
What happens at the network layer?
Adds source and destination IP addresses
Routers use IP addresses to forward packets
What happens at the link layer?
The connection between the network devices
Adds the MAC address identifying the NIC of source and destination computer
Describe the layers of the TCP/IP stack on the recipient computer.
Link: Removes MAC addresses
Network: Removes IP addresses
Transport: Removes port number and reassembles packets
Application: Present data in form it was sent
What is a LAN?
A network spread over a small geographical area typically located on a single site
Hardware usually owned and controlled by the organisation using it
What is a WAN?
A network that covers a large geographical area
Infrastructure leased from telecommunication companies who own and manage it
What is a Domain Name System?
Method of naming internet resources
Hierarchy where each smaller domain is seperated from larger by a full stop
What is the purpose of a DNS server?
Translate domain names into IP addresses when accessing a website
What is circuit switching?
A method of communication where a direct link is created between two devices and maintained for entire conversation
What is the advantage of circuit switching?
Quicker reconstruction as data arrives in logical order
What are the two disadvantages of circuit switching?
Devices must transfer and recieve data at the same rate
Electrical interference from switches can corrupt or lose data
What is packet switching?
A method of communicating packets of data across a network
What are the three advantages of packet switching?
Methods to ensure data arrives
Multiple routes if one breaks
Can transfer packets over very large networks
What is the disadvantage of packet switching?
Time is spent deconstructing and reconstructing data packets
How are data packets split?
Header
Payload
Trailer
What is included in the header of a packet?
Sender & recipient IP addresses
Protocol being used
Order of packets
Time to live / hop limit
What is included in the payload of a packet?
The raw data
What is included in the trailer of a packet?
Checksum / cyclic redundancy check
What is the hop limit of a data packet?
Set by the source of the packet
Decremented by one each router (hop)
Why is a hop limit needed?
To prevent data packets from circulating indefinitely with a network
What is the checksum of a packet?
Value computed from a data packet to check whether data is received error free or not
What is a firewall?
Device designed to prevent unauthorised access to a network
Describe how a firewall works.
Two NICs between user and internet connection
Pass packets between two NICS and compares them against packet filters
Perform packet filtering
What are packet filters?
A set of rules set by the firewall software
What are proxy servers?
Intermediate that collects and sends data on behalf of user
Give 3 features of proxy servers.
Protect privacy of usr who remains anonymous
Cache frequently used website data so faster to load
Reduce web traffic
Give a use of proxy servers.
By administrators to prevent access to sensitive or irrevelant information at work/school
What is a Network Interface Cards?
Required to connect a network
Assign a MAC address to each device
What is a switch?
Used to direct the flow of data across network
Used in star topology
What is a Wireless Access Point?
Allows devices to connect to a network wirelessly
More commonly used to connect devices to a router
Used in mesh networks
What is a router?
Used to connect two or more networks
Includes ISPs network to allow Internet connection
What is a gateway?
Translates protocols so that both networks have same protocols
Removes the header from packets before the remaining data is added with the new protocol of the new network
What is a client-server network?
Terminals conncted to a server
What is a client?
A terminal
What is a server?
Powerful central computer
Holds all important information and has extra processing power the clients can request to use
What are the three advantages of a client-server network?
More secure
Central backups
Sharing data and resources
What are the three disadvantages of a client-server network?
Expensive set up
Trained staff are required to maintain server
Single point of failure
What is a peer-to-peer network?
Computers are all connected
What are the three advantages of a peer-to-peer network?
Inexpensive set up
Allows users to share resources
Easy maintenance
What are the two disadvantages of a peer-to-peer network?
Less secure
No central backup
