Networks

Networks

1. Network Protocols

   • Email
     • Post Office Protocol(POP)
       • RECEIVE emails
       • STORED on SINGLE device (can access OFFLINE)
     • Internet Message Access Protocol (IMAP)
       • RECEIVE emails
       • ACCESSED from MULTIPLE devices (need internet connection)
     • Simple Mail Transfer Protocol (SMTP)
       • SEND emails
   • Internet
     • Hyper-Text Transfer Protocol (HTTP)
       • REQUESTING and DELIVERING HTML files
         • Hyper-Text Transfer Protocol Secure (HTTPS)
           • ENCRYPTED connection
     • File Transfer Protocol (FTP)
       • SEND files from one NODE to ANOTHER
     • Transmission Control Protocol/ Internet Protocol (TCP/IP)
       • COMMUNICATION process (Layers)
         • 1. Application, 2. Transport, 3. Internet, 4. Network
           • ORDER: No.1-4 SEND. No.4-1 RECEIVE
           • 1. Where APPS are being USED (HTTP/S, FTP, SMTP. IMAP, POP, DNS)
           • 2. SETS UP COMMUNICATION & RULES between HOST (TCP)
           • 3. Puts DATA in PACKETS and gives ADDRESS (IP)
           • 4. Network Hardware SENDS data from SENDER to RECIPIENT (Hardware/Ethernet/WiFi)
       • HOW data is TRANSFERRED through a network
         • e.g. via Internet of VPN
     • HyperText Markup Language (HTML)
       • Writing WEB PAGES for DISPLAY
   • RULES that govern COMMUNICATION between NODES

2. Types

   • LAN
     • SMALL AREA that covers a single BUILDING or SITE
     • E.g. House or School
   • WAN
     • LARGE Geographical AREA of at least 1 MILE
     • E.g. Internet

3. Roles

   • CLIENT SERVER
     • Client makes REQUEST Server RESPONDS
     • Needs team to Manage. Good Security. Clients dependant on Server. Easy to back up as files stored centrally
     • Server handles Printing, Logins & Security, Internet Access & File Handling
   • PEER TO PEER
     • All nodes considered EQUAL
     • Poor Security. Slow nodes can slow down network. Easy to set up, difficult to maintain. Not dependant on server. Difficult to back up

4. Internet

   • DNS
     • Domain Name represents an IP. e.g. bbc.co.uk. Easier to remember as it uses words rather than numbers
     • Domain Name Server stores list of Domain Names and associated IP addresses
   • The Cloud
     • Remote Storage
     • Can access files from anywhere WITH CONNECTION. Automatic Updates. Vulnerable to attacks
   • VPN
     • Entirely Software Based
     • Encrypted Connection

5. Hardware

   • Switch
     • Connects computers together but send packets of data only to the intended destination
   • Hub
     • Hubs receive signals from a device and rebroadcast them to all connect nodes.
   • WAP
     • Used to connect Wi-Fi enabled devices to a wired network without the need for cables.
   • Router
     • A device that sends data packets between networks. They provide connections between nodes, making decisions about where to send data and by what route.
     • Journey of a Packet
       • Packet Switching
         • Using the least congested route
       • 1. Message split into equal sized chunks called packets. 2. Each packet given a order number & IP address. 3. Packets sent on route 4. Reciever waits for packets to arrive, if all do packets are placed in order and message displayed 5. If packets are missing, it waits, requests the data again and displays an error message
   • NIC
     • Used to connect a device to a network
       • MAC vs IP Address
         • MAC- Unique identifier for devices on a network (LAN)
           • Hex, fixed on NIC
         • IP: Unique identifier for devices on the internet
           • Numbers & Can change
   • Ethernet
     • Transmission Media
     • Wired vs Wireless
       • Wireless
         • Wi-Fi Frequency: The rate at which the signal changes
           • A channel is a range of frequencies that will transmit data. Can reduce interference
         • Not fixed to location, cheap due to lack of cables. Suffers from interference & poor security
       • Wired
         • Fixed to point, expensive. Good security, strong signal
         • Ethernet
           • A set of rules or protocol for linking computers together to form a LAN

6. Security

   • Threats
     • Malware
       • Malicious Software
         • Anti-Malware Software. Good Network Policy e.g. Web
         • E.g. Virus, Spyware, Ransomware, Worms, Trojan Horse
     • Phishing
       • Fraudulent Emails tricking users to giving data
         • Good Network Policy e.g. Email
     • Social Engineering
       • Using people as the weak point- Tricking to sharing data
         • Good Network Policy e.g. Email
     • Brute Force
       • Trail & Error passwords to gain access
         • Good Network Policy e.g. Password
     • DDOS
       • Flood the server with requests
         • Firewall
     • SQL Injection
       • Adding malicious code to existing SQL statements to delete/modify database
         • Validation
         • Penetration Testing
     • Hacking
       • Gaining unauthorised access
         • Firewall
     • Data Interception
       • E.g. Packet Sniffing- Intercepting packets on route
         • Encryption

7. Topology

   • STAR
     • Nodes connected to central Switch/Hub
       • Reliable- One Node goes down, network unaffected.
       • Central Switch whole Network Fails
       • Easy to add/remove nodes
   • MESH
     • All nodes are interconnected
       • Alternative routes available if nodes fail
       • Expensive due to cabling
       • Easy to add/remove nodes

8. TWO+ Devices connected together in order to COMMUNICATE

   • ADVANTAGES: Share peripherals. Share files/software licenses. Easy backup and Good Security. DISADVANTAGES: Hardware expensive, threat of viruses & hacking

9. Bandwidth & Latency effect performance

Imagens e arquivos do mapa