Network Topology

• show understanding of a bus topology network and the implications of how packets are transmitted between two hosts

• show understanding of a star topology network and the implications of how packets are transmitted between two hosts

In Data communications

• Sender
• Receiver
• Transmission medium - Carry the message, physical
• Message - Both ends required to have an agreed protocol to send
• Protocol

Network Topology - how physically devices connected in a single (isolated) network

Network Hardware Devices

• show understanding of a wireless network

• explain how hardware is used to support a LAN: switch, router, servers, Network Interface Cards (NICs), wireless access points

• show understanding of Ethernet and how collision detection and avoidance (such as CSMA/CD) works

Wireless Networks

Research and complete the table

LAN hardware

• Router
  • Routes (path planning) for packet from one network to another
• Network Interface Card (NIC)
  • The hardware component that allows the device communicate with other devices
• Wireless Access Point (AP)
  • Hardware device allow other WiFi device to connect to wired network
• Hub / Switch
  • Provide wired connection to multiple devices, distribute packets to connected devices
  • Central device in a Star network

Hub vs Switch

• Hub
  • "broadcast" all incoming message
  • i.e. re-transmit to all connected devices
• Switch
  • inspect the packet to determine the destination of the packet
  • Only forward the message to designated recipient
  • Switch work in Layer 2 (Data link layer) of OSI model, and it inspect the MAC address of the packet

TCP/IP Protocols

• Show understanding of why a protocol is essential for
  communication between computers
• Show understanding of how protocol implementation
  can be viewed as a stack, where each layer has its own
  functionality
• Show understanding of the TCP / IP protocol suite
• Show understanding of protocols (HTTP, FTP, POP3,
  IMAP, SMTP, BitTorrent) and their purposes

TCP/IP Protocols

• TCP - Transmission Control Protocol
• IP - Internet Protocol
• TCP/IP Suite is a stack of many different protocols:
  • Link Layer (network interface)
  • Network layer
  • Transport layer
  • Application layer
• Upper layer will communicate with the next immediate layer and relying on it to take care all lower level actions
  • e.g. HTTP (application layer) can send data via any physical layer (e.g. ethernet, bluetooth) without changing any implementation, since it relies on TCP (transport layer) only

OSI compares to TCP/IP model

TCP/IP model with some example protocols

Network Layer (OSI layer 3)

• Data packets
• Internet Protocol, IP Address
• Ensure data packet correctly routed over the Internet
• Router is a layer-3 device which compares to switch is layer-2
  • Router routes data packets (with IP address)
  • Switch distributes data frames (with MAC address)
  • What about hub?

Ethernet Data Frame

Dataframe vs Data packet

Data is wrapped in different layers across TCP/IP Suite

Transport Layer (OSI Level 4)

• TCP
  • ensures message is safely delivered to the receiver
  • also ensure response can be directed back to the application protocol
    • On top of IP address, port is defined
    • Port is virtual and refers to different communication channel over the same IP address
  • TCP is connection-oriented, which means a virtual connection will establish between devices, while IP or lower levels are connection-less

Application Protocols

• HTTP/S
• FTP
• Email
• P2P

FTP

• File Transfer Protocol
• Design for clients to upload and download files from a file server

Email Protocols

P2P Protocol

• BitTorrent is a peer to peer (p2p) protocol which allows files to be shared, without hosting the files in server
• https://www.youtube.com/watch?v=6PWUCFmOQwQ
• Watch and answer:
  • How BT different from downloading from server
  • What is Tracker and Peer

Transmission Modes

• show understanding of circuit switching and where it is applicable
• show understanding of packet switching
• show understanding of the function of a router in packet switching
• explain how packet switching is used to pass messages across a network, including the Internet

Circuit Switching

• Circuit switching requires establishing dedicated physical connection between devices
• Example: Traditional Telephone switching system (PSTN)

Packet Switching

• Instead of dedicated connection, connections are shared in packet switching
• Data is splitted into small chunks, call packets
• Each packet has headers identifying source and destination address, along with other control data
• Packets take different pathway to the destination
• On the Internet, packets are forwarded by Router