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)

Important points for Chapter 1

1) The function of a router is to connect different LANs and WANs together, providing the best paths to these networks. The function of a switch is to connect multiple end devices together within the same LAN. The function of a hub is the same as the switch but it is a slower version of a switch. The function of a repeater is to boost up the signals over large distances. The function of end devices (PCs, laptop and mobile phones) is to create data, send and receive them.

2) Serial cables are used to connect WANs and they are used only by routers. Ethernet cables are used to connect LANs and they are used by all devices.

3) 3 types of ethernet cables - Straight through, crossover and rollover cables
    Same devices use crossover cables to connect
    Different devices use straight through cables to connect
    Special case :  Router to PC, Switch to Hub uses crossover cables although they are different devices.

4) WAN - covers wide geographical distance and use only serial cables
     LAN - covers small geographical distance and use only ethernet cables

5) 4 elements of a network
    Devices (Routers, Switches, Hubs and End devices), Medium (Ethernet cables and serial cables), Messages (Data, Segment, Packet, Frame) , Rules (TCP and UDP protocols)

6) 4 characteristics of a network
    Fault tolerance, Scalability, Quality of Service and Security

7) We also go through how to use packet tracer (how to connect the devices, setting the PC ip addresses)
 

Summary of different modes and hostname/password commands

REMEMBER YOU MUST BE IN THE RIGHT MODES TO EXECUTE THE RIGHT COMMANDS.

For NWF, there are 3 main modes for now

User mode (denoted by the ">" sign)

Router>

Priviledged mode (denoted by the "#" sign)

Router> enable

Router#

Global config mode (denoted by the "(config)#")

Router# configure terminal or conf t (short form)

Router (config)#

To return to the previous mode, type exit

For example, to return to user mode from global config mode, use the following

Router (config)# exit

Router# exit

Router >

There are 4 passwords you will need to configure in the router.

1) Console password - The password you used when you first log in to the router. There is only one console session which is numbered "0"

router(config)# line console 0

router(config)# password XXX

router(config)# login

Remember to type login to activate the password

2) Enable password - The PLAINTEXT password you used after you type "enable"

router(config)# enable password XXX

3) Enable password - The ENCRYPTED password you used after you type "enable". Cisco router will use it instead of the PLAINTEXT password.

router(config)# enable secret XXX

4) Telnet password - The password you used when you telnet into the router (seldom used in NWF). There are 5 telnet sessions supported, which are numbered from "0" to "4".

router(config)# line vty 0 4

router(config)# password XXX

router(config)# login

Remember to type login to activate the password

To configure hostname, use the command

router (config)# hostname XXX

Knowing all these will help you score good grades in the semester later on.