SLR 11 & 12 Flashcards
What is a network
two or more computers connected together with the ability to transmit data between each other
WHt are the two main types of network
local area network (LAN), wide area network (WAN)
What is LAN
a network which is spread over a small geographical area, e.g. a school.
what is WAN
a network which is spread over a large geographical area, e.g. large corporations with several offices.
what are the two types of network topology
physical topology, logical topology
What is physical topology
the physical layout of the wires and components which form the network (e.g. bus, star, mesh)
what is logical topology
the layout which shows how data flows in a network
what is physical bus topology
all the devices are connected to a backbone cable, which is connected at the ends to terminators.
what are advantages and disadvantages of bus topology
Adv.: inexpensive, no additional hardware.
Disadv.: if backbone fails whole network fails, as traffic increases performance decreases, all conputers can see data transmission.
What is physical star topology
using a central node (often a switch) that all machines are connected to, to direct data through a network.
what are advantages and disadvantages of star topology
adv.: consistent performance, if one cable fails only one terminal is affected, transmits data faster, easy to add new stations, no data collisions
disadv.: expensive, if central switch fails whole network fails
what is physical mesh topology
every node connected to every other node
what are advantages and disadvantages of mesh topology
adv.: if using wireless network no cabling cost, nodes automatically incorporated, no central switch.
disadv.: if wired lots of cable cost, difficult to maintain
what is a protocol
a set of rules defining how two computers communicate with each other. they are standard so all devices have designated method of communicating.
what are examples of commonly used protocols
HTTP (Hyper-Text Transfer Protocol), TCP/IP (Transmission Control Protocol/Internet Protocol), POP3 (Post Office Protocol), IMAP (Internet Message Access Protocol), FTP (File Transfer Protocol)
What is the internet
a network of networks which allows computers on opposite sides of the globe to communicate with each other.
What is the TCP/IP
A stack of networking protocols that work together passing packets during communication.
what are the layers of the TCP/IP stack
Application layer, transport layer, network layer, link layer
What is the application layer of the TCP/IP stack
At the top of the stack, specifies what protocol needs to be used in order to relate the application that’s being sent.
What is the transport layer of the TCP/IP stack
Used TCP to establish end-to-end connection between source and recipient, splits data into packets and labels packets with packet number. If any packets get lost, transport layer requests retransmission of these lost packets
what is the network layer of the TCP/IP stack
adds the source and destination IP addresses. routers operate on the network layer and the router is what used the IP addresses to forward the packets, the dockets are then used to specify which device the packets must be sent to and the application being used on that device.
WHat is the link layer of the TCP/IP stack
connection between network devices, it adds the MAC address identifying the Network Interface Cards of the course and destination computers.
What is a DNS
Domain name system is system used to name and organise internet resources.
What are data packets
segments of data containing various information.
what information does data packets contain
Header: Sender & recipient IP addresses; the protocol being used; the order of the packets; the Time To Live (TTL) / Hop Limit.
Payload: Raw data to be transmitted
Trailer: Checksum (or cyclic redundancy check)
Why are the sender and recipient IP Addresses included in data packets
they act like a postcode, allowing the packet to be delivered to the correct destination and enabling the recipient device to trace where the packet came from.
why is the protocol being used contained in data packets
the protocol allows the recipient computer to understand hoe to interpret the packet
why is the order of packets included in data packets
Upon arriving at the recipient device, packets are reconstructed in the appropriate order as specified in the header.
why is the Time To Live/Hop Limit included in data packets
tells the packet when to expire so that it does not travel forever
What are the two techniques used when networks exchange data
circuit switching and packet switching
what is packet switching
method of communication in which data is communicated using packets across a network
what are adv and disadvantages of packet switching
adv.: multiple methods to ensure data arrives intact, multiple routes can be used between devices, packets can be transferred over large networks
disadv.: time is spent de- and reconstructing data packets, must wait until all packets arrive before data can be received.
what is circuit switching
direct link s created between two devices. the link is maintaned for the duration of the conversation between devices. requires two devices to transfer and receive data at the same rate
what are adv. and disadv. of circuit switching
adv.: data arrives in logical order which results in quicker reconstruction of data, enables two users to hold a call without delay
disadv.: bandwidth wasted during periods of time when no data is sent, devices must transfer and receive data at the same rate, electrical interference may be produced which can corrupt or destroy data, ties up sections of the network which cannot be used by others neil transmission is complet.
what is a firewall
a device designed to prevent unauthorised access to a network. it consists of two network interface cards (NICs) between the user and the internet. the firewall passes the packets between these two NICs and compares them against a set of rules sent by the firewall software.
what is packet filtering/static filtering
limits network access in accordance with administrator rules and policies. it works by examining source IP, destination IP, and the protocols being used as well as the ports being requested.
what two thing can happen when access is denied by a firewall
the packet can either be dropped or rejected. a rejected packet sends an alert to a sender to notify them of the error whereas a dropped packet will not
what is a proxy server
acts as an intermediary, collecting and sending data on behalf of the user. there are several benefits of using proxies.
what are the benefits of using proxies
privacy of user is protected, server can cache frequently used website data making it faster to load, can reduce web traffic, can be used to prevent access to sensitive or irrelevant content at work/school
what is encryption
a way of keeping data secure when transmitting data over the internet. it makes data unreadable if it is intercepted.
what is a network interface card
NIC is a card required to connect a device to a network. usually built into the device and assigns a unique media access control (MAC) address to each device.
what is a MAC address
a 48-bit value code into the device and usually written as a twelve digit hexadecimal number
what is a switch
a device used to direct the flow of data across a network
what is a WAP
WIreless Access Point, a device to connect to a network, it is more commonly combined with a router to enable internet access.
what is a router
used to connect two or more network together. allows private, home networks to connect to the internet
what is a gateway
used when protocols are not the same between networks. translates protocols so that networks can communicate with each other. they work by removing the header from packets before adding the data to packets using the new protocol
what is a client-server network
network consisting of terminals (clients) connected to a server
what is a server
a powerful central computer. holds all the important information and resources and has a greater processesing power
