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AS 1.3.3 - Networks


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network
two or more computers that exchange data
internet
a network of networks that allow computers to communicate with each other globally
World Wide Web
a collection of web pages that reside on computers and servers connected to the internet
Internet Service Provider
they connect directly to the backbone cables of the internet which run through each continent (connected by trans-continental cables), and then distribute the internet connection to others
Uniform Resource Locator
the full address of an internet resource, which specifies its location on the internet, resource name and often file type
Internet Registrars
companies that hold records of all existing website names and details on those domains that are currently available to purchase; they sell the domain names on to people and companies
Internet Registries
five global organisations governed by the ICANN with worldwide databases which hold records of all domain names currently issued to individuals and companies, and their details, including the IP Address they're linked to
Internet Corporation for Assigned Names and Numbers
ICANN - a non-profit organisation responsible for coordinating the maintenance and procedures of databases regarding internet namespaces
Domain Name System
the system in which a domain name (or URL) is translated into its corresponding IP address, so the server can be accessed to request a web page
Domain Name
linked to an IP address, identifies the area or domain that an internet resource resides in
Fully Qualified Domain Name
a domain name that includes the host server name, ie. whether it is hosted on a web (www), mail or ftp server
Internet Protocol Address
a unique address (to that network) that is assigned to a network device, which indicates where a packet of data has been sent from or is being sent to
Wide Area Network
a network of interconnected networks, which typically spread over a large geographical area and rely on third party carriers/connections
Local Area Network
a network where the computers are connected using their own cabling and topology structure, often within an organisation and covering a small geographical area
Bus Topology
a LAN where all computers are connected to a single cable, and the ends of the cable are plugged into a terminator
random timer
On a bus topology network, if a data collision occurs, their data transmission requests are withdrawn, and then what is started to determine when they can attempt to send their request again?
hardware
Advantage of Bus Topology: inexpensive to install as it requires less cable than a star topology and doesn't require additional...
backbone cable
Advantage of Bus Topology: All nodes on the network have equal rights to the network resources via the...
nodes
Disadvantage of Bus Topology: if the main cable fails, data cannot be transmitted to ANY...
degrades
Disadvantage of Bus Topology: with heavy traffic, performance...
low security
Disadvantage of Bus Topology: all computers on the network can see all data transmissions, meaning there is...
Star Topology
a LAN with a central node (ie. hub or switch), which acts as a router to transmit messages
Hub
a common connection point between devices in a network; it receives a signal from a node, and then broadcasts it to all nodes in the network (not just the intended one)
Switch
a device used in a star network as a central node, which will keep a record of the unique MAC address of each node on the network and will then transmit data directly to the intended computer, not all nodes
isolate faults
Advantage of Star Topology: If one cable fails, only one node is affected, so it is easy to...
consistent
Advantage of Star Topology: With heavy traffic, the performance remains...
data collisions
Advantage of Star Topology: As each node has its own cable to the server, there are no...
secure
Advantage of Star Topology: Messages are sent directly between the nodes and switch, so cannot be intercepted and thus is more...
disrupting the network
Advantage of Star Topology: It is easy to add new nodes without...
expensive
Disadvantage of Star Topology: Due to the large amount of cable required, instalment may be...
central device
Disadvantage of Star Topology: The entire network will go down if what fails?
Ring Topology
a LAN in which all devices/nodes are connected to two other devices each, forming a ring
token passing
a token, or series of bits, to grant a device permission to transmit over the network (used in a RING topology)
empty
In token passing, a node can only send data when it has a token, if a token is already full with data, it must wait for another token to reach it, which is...
data frame
the token is filled with a ... , as well as the source and destination address, once a device has requested to use it to transmit data on the ring topology network
flag
In a ring topology, what is switched to indicate that the token is busy (ie. being used by a device to transmit data)?
transmission rates
Advantage of Ring Topology: As data collisions cannot occur, this topology allows for high...
resources
Advantage of Ring Topology: Each node has equal access to network...
load
Advantage of Ring Topology: Performance is not affected by having additional components, and is better than the performance of a bus topology, even with an increased...
slower network
Disadvantage of Ring Topology: Each packet of data must pass through every device between the source and destination nodes, potentially making it a...
affected
Disadvantage of Ring Topology: If one node or cable fails, the whole network will be...
device
Disadvantage of Ring Topology: The whole network must go down / be taken offline, in order to add another...
physical topology
the physical design / layout of how devices are connected on a network with cables
logical topology
the way in which components communicate across a physical topology, thus being how devices appear to be connected to each other
ethernet
the standard way to connect computers on a network over a wired connection, which uses a logical bus topology when components communicate, regardless of the physical topology being used in the network
WIFI
a local area wireless technology that enables a device to connect to a network resource or to the internet via a WAP
Wireless Network Access Point
WAP - a networking hardware device that allows a Wi-Fi compliant device to connect to a wired network
Mesh Topology
a network where each node has a connection to every other node (by transmitting data through intermediate nodes)
all other nodes
In a mesh network topology, if one node has a connection to the internet, who else has a connection to the internet?
cabling
Advantage of Mesh Topology: There are little/no costs for...
reliable
Advantage of Mesh Topology: As more nodes are installed on the network, the network becomes faster and more...
self healing
Advantage of Mesh Topology: If a connection is blocked or broken, it can be circumvented by another route, making this topology...
faster
Advantage of Mesh Topology: As data packets do not need to travel via a central switch, communication is...
difficult
Disadvantage of Mesh Topology: Set up and maintenance can be...
Circuit Switching
a type of communication on a network where a physical connection is made between two computers / nodes for the duration of the transmission, and all packets are sent sequentially down this same path (circuit)
public telephone system
Example of a network that uses circuit switching
transfer rate
Circuit switched networks can only connect devices or nodes that operate at the same (data)...
reconstructed
Advantage of Circuit Switching: as packets are sent and received in the same order, at the recipient end, it is easier and quicker for the message to be...
electrical interference
Disadvantage of Circuit Switching: as switches are used to connect and disconnect the circuits, what is produced, which may cause corrupt or lost data if the path is used for transmitting data?
quickly
Disadvantage of Circuit Switching: lots of users, all requiring their own line on the network at the same time, would require a large network, which would be expensive, and as the user numbers increase, the network would have to expand...
Packet Switching
a type of data transmission in which the data is split into packets, each holding its own information, thus allowing each packet to take different routes to the destination
confirmation
In packet switching, if a collision happens and a data packet is lost, the source computer will resend the data after a certain amount of time, if it hasn't received (from the destination computer) a...
lines
Advantage of Packet Switching: it makes efficient use of the networks, as it doesn't tie-up ...
broken parts of the network
Advantage of Packet Switching: data packets can reroute and bypass...
slowly
Advantage of Packet Switching: compared to circuit switching, as the customer/user numbers increase, the network only has to expand...
time-critical information
Disadvantage of Packet Switching: the time it takes to reassemble the data packets changes each time, which can be a problem for...
small
Disadvantage of Packet Switching: it becomes inefficient when trying to send ... data packets
packets
Data that needs to be transmitted across a network is broken down into smaller data...
header
Contained by a data packet, which specifies the sender and recipient IP addresses, protocol being used for the packet, the number of the packet in its sequence and TTL information
Time to Live
the number of hops that a packet is permitted to travel before being discarded by the next router (ie. to prevent data packets getting lost and travelling round a network forever)
payload
Contained by a data packet, which itself contains the actual data being sent
extracted
When packets are received, they are reassembled into the correct order and then the data is...
Cyclic Redundancy Check
a code added to data which is used to detect errors occurring during transmission, storage, or retrieval
checksum
a digit representing the sum of the correct digits in a piece of stored or transmitted digital data, against which later comparisons can be made to detect errors in the data
trailer
Contained by a data packet, and will hold either a checksum or CRC to detect any errors or corruption that may have happened in transmission
hash total
the total created from the data when using a checksum or CRC, if the recalculated one on the recipient end does not match the original one, then the packet is refused and a new copy of the data is requested
fastest route
Data packets being sent across the internet will either take the shortest route (ie. number of routers to pass through) or the ... (ie. by bandwidth)
Media Access Control Address
a unique identifier assigned to all network-compatible devices (ie. devices with a NIC in them), which is then used at the datalink layer of the TCP/IP stack
Network Interface Card
a device within a machine (often connected to the motherboard) that allows it to connect to a network
12
a MAC address is written as how many hex digits?
Protocol
a set of rules that define how devices communicate with each other, which must be followed for communication to take place
Standard
a definition or format that has been approved by a recognized standards organization or is accepted as a de facto standard by the industry
TCP/IP Stack
a set of network protocol layers that work together and define how communication is carried out over the internet
Protocol Layering
a common technique to simplify networking designs by dividing them into functional layers, and assigning protocols to perform each layer's task
four layers
The TCP/IP Stack uses protocol layering, where the ... of protocols work together during network communication
Application Layer
Top layer of the TCP/IP stack, at which a user requests to transmit data information through the application they are using (e.g. a browser)
HTTP, POP3, FTP
the application layer uses protocols relating to the application being used, usually higher-level protocols, such as...
Hypertext Transfer Protocol
HTTP - has become the standard protocol for rendering web pages in browsers
Post Office Protocol v3
POP3 - responsible for retrieving emails from a mail server which temporarily stores the incoming mail
File Transfer Protocol
FTP - a very efficient method used to transfer data across a network
Transport Layer
Second layer of the TCP/IP stack, which establishes an end-to-end connection with the recipient computer and the data is split into smaller data packets
retransmission
At the transport layer, the data packets are labelled with the packet number, total number of packets, and port number. This layer at the receiving end will acknowledge receipt of packets and if any packets are missing, will request...
TCP
the transport layer uses which protocol, which establishes an end-to-end connection with the recipient computer?
Transmission Control Protocol
TCP
Network Layer
Third layer of the TCP/IP stack, which adds the source and destination IP addresses, and Time to Live information to the data packets
socket
specifies which device the packet must be sent to and the application being used on that device, formed from the addition of an IP address to a port number, e.g. 42.205.110.140:80
IP
example of a protocol used by the Network Layer
Internet Protocol
IP
destination
Routers operate on the network layer by using the IP addresses to forward the packets on to the...
Router
a device that forwards packets from one network to another (but not data from a network to a different device in the same network); it changes the MAC address on a packet to route it to its destination, without changing the IP address of the packet
Data Link Layer
Bottom layer of the TCP/IP stack, which is the physical connection (ie. cables) between network nodes and adds the MAC addresses of the source and destination devices
router node
When a data packet is being transmitted across the internet, the destination MAC address will be the MAC address of the next router on the route and is changed by the...
PPP, OSPF
examples of protocols used by the Data Link Layer
Point-to-Point Protocol
PPP
Open Shortest Path First
OSPF Protocol
anonymous use
FTP is used by clients and servers to transfer files (often simply by dragging and dropping in a graphical interface) on a network, and FTP sites may require authentication (ie. username and password) or could be configured for...
Mail Server
act as a virtual post office for all incoming and outgoing emails, by routing mail according to its database of local network user's email addresses, and store the emails until they can be retrieved
deleted
When an email has been retrieved from a mail server (using POP3), it is transferred to the local device and the temporary copy on the server will be...
multiple devices
Disadvantage of POP3: as emails are deleted from the mail server once downloaded to the device, emails wont sync on...
Internet Message Access Protocol
IMAP - another email protocol, which is designed to keep emails on the mail server (unlike POP3), which allows syncing of emails between devices
Simple Mail Transfer Protocol
SMTP - protocol used to transfer outgoing emails from one server to another, or from an email client to a server
Server
a computer or device on a network that is used solely to provide a specific service to other devices on the network, or to manage network resources
Repeater
uses a weakened signal that has travelled a long distance, and refreshes it so that it can be sent along another length of cable (however, this can only be done a limited number of times before the signal becomes too distorted)
Client-Server Network
a network where one entity (the client) makes requests to another entity (the server, e.g. a file server). The server will store all the security information, such as logins and permissions.
File Server
server which holds and manages data for all the clients
Print Server
server which manages print requests
Web Server
server which manages requests to access the Web
Database Server
server which manages database applications
central location
Advantage of Client-Server: security is better as all access rights are managed by the server and all files are stored in a ...
restored
Advantage of Client-Server: as all files are at a central point, it is quicker and easier for the data to be backed up or...
shared
Advantage of Client-Server: data and other resources can be...
remotely
Advantage of Client-Server: servers can be accessed...
manage
Disadvantage of Client-Server: it is expensive to install and ...
hired
Disadvantage of Client-Server: the servers and network needs to be run and maintained, so professional IT staff would have to be...
congestion
Disadvantage of Client-Server: too many requests from clients could lead to...
Peer-to-Peer Network
a network where all computers have equal status and they all act as both a client and a server. Each individual computer will store its own security information and data. This network is popularly used for music sharing, and the internet payment system, Bitcoin.
printers and routers
Advantage of Peer-to-Peer: good for a home or small office because it is cheap and easy to set up, is not difficult to maintain, and allows users to share resources such as...
other peers
Advantage of Peer-to-Peer: does not depend on the central point, the failure of one peer does not affect the functioning of ...
torrent websites
enable the sharing of files online, which often contain copyright material, which uses a Peer-to-Peer network, as each computer can hold part of the file, therefore sharing the load, when many users want to download it
impossible to trace
Disadvantage of Peer-to-Peer: these networks are often used for online piracy, as the files being illegally downloaded are nearly ...
backup system
Disadvantage of Peer-to-Peer: the network is decentralised so is more difficult to administer, and each computer must have its own ...