Networks

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  • Created by: jacksie
  • Created on: 13-11-19 15:21
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  • Factors of networks
    • Networks
      • hardware
        • Nic
          • internal bit of hardware
          • usually on motherboard
          • allows device to connect to a network
        • Switch
          • switch transfers data in a network
            • Transfers data with the right MAC address
        • Router
          • transfers data between networks
          • important in transferring data in the ineternet
            • they transfer units called packets
      • wireless
        • wireless networks uses radio waves
          • they need a WAP, wireless access point
            • to connect wirellessly, they need capability
              • but you can use a dongle
                • dmi dongle used for streaaming
        • WiFi
          • transfers around 2.4 to 5 ghz
            • 2.4 covers a larger range
            • 5 is quicker
          • the connection is split into a number of channels that overlap
      • peer-peer and client server
        • Clirnt server
          • stores data centrally in the server
          • The client makes a request, processed and executed by server
            • server stores users, passwords, data
              • some functions need a required password
          • pros and cons
            • Central storage, easier to backup
              • More secure
            • however, hard to maintain
              • needs IT specialist
        • peer-peer
          • P2P, is more for domestic LAN
          • No centralised management
            • Backing up data has to be done individually
              • May lead to multiple copies that aren't needed
          • doesn't rely on a server
            • will run if a node fails
      • Topolgies
        • Star Network
          • A central switch in the middle
            • Allows fewer data collisions than a bus
            • More than one device can run
            • Needs IT specialist
            • in a wireless network, easy to add a node
            • hardware may be expensive
            • however may be expensive with an office with 50 terminals
            • if switch or server crashes whole network fails
        • Ring and bus
          • problem of data collisions and the fact that only one device can transfer
        • Mesh
          • Ideal
            • if a node fails, since there are other routes
              • however, would cost a lot in a wired network
                • becoming more wireless
      • Network Protocols
        • protocols are a set of rules of how to communicate
        • MAC
          • A mac is a 64 bit or 128 bit binary num,ber
            • Created by the manufacturer
              • they are the unique identifier
              • permanent
            • translated into hexadecimal
        • Ip adresses
          • communicate between networks
            • IP/TCIP, are used over the internet
              • there are two types: static and dynamic
                • static IP
                  • they are permanent, meaning they don't change
                  • Big companies pay a lot for static ip
                    • This is because they don't wanthe Ip adress to change
                • dynamic IP
                  • THis is changes
                    • used by ISPs
                      • internet service providers
                      • more cost effective
              • either a 32 bit or 128 bit binary number
                • 32 bit is translated into four denary numkbers
                • 128 bit is 8 hexadecimal numbers numbers
              • Packets
                • when data is transferred it is plit into packets
                  • packets have 3 componenets
                    • header
                      • this contains the destination, this is like an envelope
                    • payload
                      • this is the contents of the packet
                        • liek the inside of a letter
                    • checsum
                      • this is  a number at the end to check data is not corrupted
                • Packet switching
                  • when transferring data
                    • data is split into packets
                      • a router reads the packet header and decides the way it travels depending on IP rules
                        • If a router recives to many packets it may priotise some
                          • Some packets may be lost, so it checks periodically all packets are there, if so a timeout message is sent
                            • the packets may not be order so they are arranged
                              • If the checksum is coorect, a reciept confirmation is sent
        • IP/TCP
          • TCP, is in charge of splitting data into packets
            • Other protocols build upon IP/TCp
              • HTTP
                • hyper text transefr protocol
                  • transfer data from browser to web server
                • HTTps
                  • encrypts all data
              • FTP
                • used to transfer files between devices on a network
              • POP3
                • Post office protocol
                  • retrieves email from a server
                    • deltes from the server once you download it
              • IMAP
                • intternet message aaccess protocol
                  • retrieves email
                    • deletes email when u delete
                      • web based clients
              • SMTP
                • used to send mails , and transfer emails between servers
          • Layers
            • A layer is a group of protocols with A SIMILAR FUNCTION
              • Layers are self-contained- they [email protected] know whats happening with other layers
                • Layers servethe layer above them
            • Layer 4- application
              • This layer sets up data as websites and other applications
                • https, smtp
              • Layer 3- transfer
                • this is in charge of data flow, splitting data into packets
                  • TCP
                • Layer 2- Network
                  • connections between networks, directing packets. Used by routers
                    • IP
                  • Layer 1--link layer
                    • This converts data into the lectrical signals, transfer data into a physical network
                      • Ethernet
      • Internet
        • INternet is a netwrok of networks
          • WWW is a collection of hosted web pages on a server
            • URL are adresses for a specific webpage or file
              • DNS(Domain name server- converts ip adress into a domain name
        • Hosting is when a business stores files of another
          • the most common use is the @cloud'
            • third party commpany
              • Don't need to pay for hardware
                • Don't need to pay an IT staff to manage data
                  • automated backups
                • easy to increase your storage
                  • however, subject to an attack
                    • another company has access to your fild
                      • subscription to cloud software may be expensive
        • Virtual networks
          • this is networks made on software
            • created by partitioning some bandwidth of a physical network
          • several virtual networks can exist on a physical network
            • more cost efficient
              • Each network has is its own security and fire wall
                • can have access to some of the physical network but not the virtual network
          • VPN
            • virtual private network
              • this encrypts data making it secure
                • used over WANs
                • school intanet
          • virtual LAN
            • breaks up a LAN into several networks on the same hardware
      • SEcurity
        • Passive attacks
          • they monitor quietly data being transferred and pick up sensitive software
            • they use software like packet sniffers
          • best defnse is encryption
        • active attack
          • they actively attack with malware
            • best defense is firewall
        • Insider attack
          • steals information within a network
        • Brute force attack
          • creates hundreds of likely passwords until it gets it right
            • automated software
          • create a lockout after a certain number of attempts
        • Denial of serive
          • floods a network with data
        • Malware
          • delete or modify files
          • scareware
            • says its infected with viruses
          • ransomware
            • locks files
          • monitoring data and sends it to the hscker
            • Untitled
          • viruses
            • linked to file .exe
              • spread when file is saved
              • activated when file is open
            • trojans
              • data seems legitimate but isnt
            • worms
              • self replicate without user help
          • open backdoors for future attacks
    • bandwidth
      • the amount of data that can be transferred
        • mbps
          • the better the bandwidth the greater the performance
    • for wired networks
      • the hardware
        • Fibre optic cables are faster than copper wires
    • The topology
      • peer-peer faster than client server
    • bandwidth availability
      • heavy traffic and congestion slows down networks

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