Wired and Wireless networks

Abel Miller
Mind Map by , created almost 3 years ago

GCSE Computing Mind Map on Wired and Wireless networks, created by Abel Miller on 11/17/2016.

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Abel Miller
Created by Abel Miller almost 3 years ago
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Wired and Wireless networks
1 Client server networks and peer to peer
1.1 Client server
1.1.1 The server is a powerful computer which provides services or resources required by any of the clients
1.1.2 A client is a computer which requests the services or resources provided by the server
1.1.3 Different types of servers A file server holds all the data files and databases and manages backups A print server may organise printing on different printers An email server may receive emails, detect and block spam, distribute emails to users A web server may host the school’s external website
1.1.4 Roles on the network The client sends requests to the server Waits for a reply Receives the reply The server waits for requests from a client Acknowledges the request The server may need to pass the request (e.g. for a web page) to another server – in which case, it becomes the “client” The data is sent back to the client.
1.1.5 VS A central backing store is available to all computers Security is controlled by the central computer Backup is done centrally on the server All users are reliant on the central server Can support hundreds or even thousands of users and grow with an organisation. Requires IT staff to administer and control Storage facilities are distributed across all computers Security is not centrally controlled Backup must be done separately for each computer No central server Easy to set up but most suited to homes and small businesses. Viruses easily spread. If one link goes down, then nothing else is damaged, but computers are unable to access anything from that peer.
1.2 Peer2Peer
1.2.1 Used for BBC Iplayer and illegal file sharing sites as they are difficult to close down
1.3 Cloud networking
1.3.1 All data is kept on remote server, to be accessed by wireless or cabled connections
1.3.2 Each application has a(some) dedicated server(s)
1.3.3 If you have Gmail or Hotmail, you are using it
1.3.4 Typically on a subscription basis No need to have the software installed on a local machine Can access the software (and your data) from any Internet-connected computer, including mobile phone applications
1.3.5 Online accounting packages Customer Relationship Management systems (CRMs) Share trading applications
1.3.6 Everything backed up by service provider.Applications can be accessed from anywhere with connection
1.3.7 Giving sensitive or important data to someone else to look after. More vunerable to hacking
1.3.8 Paymnent needed for more than an allowed amount of data
1.4 Transmission methods
1.4.1 Copper cables Tried and trusted Lots of energy needed, and signal boosters needed Heavy cables low bandwidth Affected by electric and magnetic fields
1.4.2 Fibre opics Safer Higher data transmission High cost Low energy Not affected by electric or magnetic fields
1.4.3 Wireless Less secure Can get it anywhere with signal Easy to add devices Lower data transmission Signal can be blocked easily
1.5 Bandwidth: the amount of data that can be carried at once, like water in a ipe
1.6 Latency: the delay between the first packet of data being sent, and the first packet being collected at the other side
1.7 Sometimes packets collide because of large amounts of data on the line. WHen this happens, they are corrupted or lost, then resent
2 The internet
2.1 A series of interconnected networks
2.2 Any network in which the computers communicate using resources supplied by a “third party carrier”, such as British Telecom, is a WAN . It is usually spread over a large geographical area
2.2.1 A Media Access Control (MAC) address is assigned to each Network Interface Card (NIC) by the manufacturer Your computer may have more than one MAC address, e.g. one for ethernet and one for wireless And a mobile phone may have two different MAC addresses – one for wireless and one for bluetooth
2.3 Internet of things:Mobile devices, parking meters, thermostats, roads, cars, supermarket shelves, kitchen appliances, dogs, cats, contact lenses, glasses, us, drinks, clothes, paper
2.4 IPV^ is the new version of IPV4. IPV4 is currently running out. These are like addresses for your mobile device
2.4.1 There are 13 DNS “root” servers worldwide which keep a complete database of all names and IP addresses Other DNS servers lower down the hierarchy hold parts of the database When a DNS server receives a request not in its database, it will pass the request on to another server until it reaches one with the matching name and IP address
2.5 Phone calls use circuit switching, with a dedicated connection between the two callers
2.6 The internet uses packet switching, where data is split into chunks, and sent down their individual fastest route
2.6.1 Each packet contains where it is going, where from, and the infomation, and some error checking info They are all sent with the same amount of bytes in, the umber of packets there are and thier packet number IP addresses change whilst moving from place to place If the client requests it, or if the server does not recieve an acknowledgement after a certain time, packeages are resent Routers move packets along their fastest route to the destination The actual geographical location of a networked device can be determined by its IP address If you take your laptop to another part of town, or to another country, its IP address will change When you request a web page, each router along the way uses the MAC address of the next router to send the data packet on the next leg of its journey The MAC address of a NIC never changes
2.7 Domain Name System (DNS) allows web addresses to be converted to IP addresses
3 Wireless networking
3.1 Data transmission
3.1.1 Commonly uses radio waves
3.1.2 Data should be encrypted because it is easily intercepted on wireless networks Wireless encryption standards Wired equivalent privacy Wi-Fi Protected Access (WPA) . WPA2 Most secure
3.2 Wireless hardware
3.2.1 Network Interface Card. Everything needs these to connect.
3.2.2 Wireless Access Point. Everything needs one of these to send out an internet signal
3.3 Frequencies and channels
3.3.1 802.11 standard 2.4 Ghz, 3.6Ghz, 5Ghz, 4.9Ghz, 5.9Ghz Each frequency is subdivided into channels
3.3.2 5Ghz higher data transmission as fewer networks on it.
3.3.3 2.4 Ghz is better at moving through objects and has a wider range.
3.4 Encryption
3.4.1 Symetric Uses the same key to decode and encode
3.4.2 Asymetric Public key, used to encode Private key, used to decode. Only the person the message is sent to knows the private key. Two large prime numbers are multiplied together. The larger the primes, the more difficult it is to work out the original numbers.
3.4.3 I Know everything I need to about codes
4 Local area networks
4.1 Generally used in schools or short range computer groups
4.2 Advantages and disadvantages
4.2.1 Advantage Sharing resources like printers saves money Access files from any computer on the network Data is easy to back up, as it is stored on a central server
4.2.2 Disadvantage Expensive to purchase the network hardware managing a large network is complicated Viruses spread more easily throughout the network
4.3 Layout
4.3.1 Mesh Partial Most computers connected FUll All computers connected Nodes act as routers for each other Advantages No single point of failure – It is a self-healing network Expansion and modification can be done without disrupting the network Data can be transmitted from different devices simultaneously Disadvantages Can involve redundant connections Expensive to install cabling if using wired connections Network maintenance and administration is difficult
4.3.2 Star Advantages Faster data transfer as there are fewer collsions If one cable fails then no other computers are affected Disadvantages Requires additional hardware such as central switch If the central device fails the whole network goes down
4.3.3 Extended star
4.3.4 Star and mesh topologies usually used together
4.4 Wireless mesh networks
4.4.1 In a wireless mesh network, only one node would need a wired connection. After this, they could be connected wirelessly. The more nodes using the network, the more the signal travels. If a node is within range of three other nodes, it will get three times the normal broadband. As the distance betwwen two nodes is halved, the signal becomes four times stronger
4.5 Hardware
4.5.1 Router-Directs packets down the fastest route
4.5.2 Hub- Sends all incoming packets to all computers on the network
4.5.3 Switch-Sends all packets to the intended reciever using MAC addresses
4.6 ethernet
4.6.1 Etherernet is a set of rules, or protocols, which which format data for transmission between computers on the same network Nodes will wait until a connection is quiet before attempting to send a message along the connection themselves Two nodes attempting to transmit simultaneously will stop and each wait a random period before reattempting
4.6.2 It splits packets into frames, similar to packets, each containing source and destination adresses and error checking data Frames are broadcast to all nodes – only the intended recipient will open the frame. Others will be discarded Frames which are detected to contain transmission errors are dropped or resent
5 Protocols and layers
5.1.1 TRANSPORT NETWORK LINK The link layer involves all of the physical hardware connecting the two hosts. HTTP HyperText Transfer Protocol. Used to access and receive web pages in the form of HTML files on the internet. FTP File Transfer Protocol.Used in the same way as HTTP IP Routes the individual packets The transport layer creates a connection between two host computers
5.1.2 TCP Transmission Control Protocol: Breaks up messages sent over the internet into packets. It re-assembles the packets at the other end. Detects errors. Re-sends lost Messages
5.1.3 SMTP Simple Mail Transfer Protocol. Used for transferreing mail between remote servers.Client email software sends message to outgoing mail server Mail server contacts destination mail server to pass on email using SMTP
5.3.1 Advantages Self contained-One layer can be affected without having to alter others All hardwares and softwares conform to the same protocols, so are all compatible
6.1 Titles
6.3 INFO

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