Important points for Chapter 2

THIS IS AN IMPORTANT CHAPTER. PLEASE READ UP.

1) Distance = mm, cm, m, km (unit of measure)
    Networking = Data, Segment, Packet, Frame, Signal (unit of measure or Protocol Data Unit (PDU)

2) Typical structure 

preamble + source mac address + dest mac address + source ip address + dest ip address + source port + dest port + data
3) Data + Ports = Segment
    Segment + IP addresses = Packet
    Packet + Mac addresses = Frame
    Frame + Preamble or Synchronization bits = Signal

4) End users use data to make decisions
    End devices use ports (inside segments) to transfer data to the correct applications
    Routers use IP addresses (inside packets) to route packets to the right network
    Switches use Mac address (inside frames) to forward frames
    Repeaters/hubs boost signals

5) Routers and switches has multiple ports and hence, multiple IP and Mac addresses
     PC has only one NIC card and therefore, only one IP and one Mac addresses

6) Information is transmitted in chunks over the internet so that multiple devices can use the internet at the same time. This process is known as multiplexing.

7) Role of an end device is to create data, send and receive data within the network. Example of end devices are PC/laptop/servers. They are mainly classified as servers and clients. Clients send requests to servers. Servers process requests from clients and send replies back to clients.

8)  Role of an intermediary device to ensure smooth data flow by transferring data from one point to another.  They are the middlemen in the network. Examples are routers/switches/hubs/repeaters.

9) By having a common protocol between different networks (such as WiFi, Internet, 3G), devices can communicate with one another seamlessly. This process is transparent to the users. It is like using English in different countries (USA, Australia, Korea, Malaysia, Indonesia, Thailand). Different people can communicate if they understand the same language.

10) Recall OSI model has 7 layers (Application, Presentation, Session, Transport, Network, Datalink and Physical). This is a textbook model called reference model. OSI model is the mother of all models.

Application - Data
Presentation - JPG, HTML, MPEG
Session - Duplex, Half duplex and Simplex transmission
Transport - Segments containing ports
Network - Packets containing IP addresses
Datalink - Frames containing Mac addresses
Physical - Signals with preamble

11) Recall TCP/IP model has 4 layers (Application, Transport, Internet and Network Access). This is a working model called protocol model.

Application - Data
Transport - Segments containing ports
Internet - Packets containing IP addresses
Network Access - Frames containing Mac addresses

12) For 2 devices to communicate with each other, they have to adopt the same model (such as TCP/IP model)