Data Communication and Networking

The route

Lessons are in the order that makes each one easier than the last. Each unit ends with a short quiz.

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   Unit 1

   Introduction to Data Communication

   Before any cable or protocol, there is a simple question: what does it take for two things to really communicate?
   1. Definition and Characteristics of Data CommunicationFree Two machines, one conversation: what it takes for data to cross a medium and still mean the same thing. 5 min
   3. Components of Data Communication and Data Flow Modes The five-member cast (sender, receiver, message, medium and protocol) is behind every text, call and download. 7 min
   4. Network Criteria, Topologies and Categories of Networks When does a chat between two machines become a network, and how can you tell if it's a good one? 10 min
   5. Unit 1 quiz6 questions on this unit 8 min
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   Unit 2 Full plan

   Network Models: OSI and TCP/IP

   Seven floors of a message, stacked so that nobody has to understand the whole Internet at once.
   1. Layered Architecture and the OSI Reference Model How do you build something as complicated as the Internet so that nobody has to understand all of it at once? 5 min
   2. Functions of the OSI Layers at the Sender and Receiver Floor by floor, down on the sender and up on the receiver, each layer talks only to its twin through the header it adds. 11 min
   3. The TCP/IP Model and Its Comparison with the OSI Model OSI was designed in committee rooms, but a scrappier four-layer model is the one actually running the Internet. 4 min
   4. Network Devices and Application Layer Protocols A hub, a switch and a router each live on a different floor — and that decides how clever each one can be. 8 min
   5. Unit 2 quiz7 questions on this unit 9 min
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   Unit 3 Full plan

   Signals, Transmission Media and Transmission Impairments

   A signal's rough journey, in which what you send is never quite what arrives, and yet the message still gets through.
   1. Analog and Digital Signals Data must become a signal: a cable cannot carry the letter A, only energy shaped into waves and pulses. 4 min
   2. Transmission Media: Guided and Unguided Copper, glass or thin air — every signal needs a road, and each road has its own speed limits and dangers. 5 min
   3. Transmission Impairments: Attenuation, Distortion and Noise A signal can fade, get bent out of shape or drown in noise — meet the three ways the wire lets you down. 9 min
   4. Data Rate Limits and Network Performance How fast can a link go? Bandwidth is how wide the pipe is; latency is how long it is. 8 min
   5. Unit 3 quiz6 questions on this unit 8 min
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   Unit 4 Full plan

   Bit Synchronisation, Line Coding and Multiplexing

   A wire carrying "0000000000" is just a flat line — so how does the receiver know how many zeros it saw?
   1. Bit Synchronisation at the Physical Layer Counting silence is hard: a receiver that loses the beat for a single bit garbles everything that follows. 7 min
   2. Line Coding Schemes: NRZ, RZ, Manchester and AMI Bits are just ideas until they become voltages — line coding draws them in a way the receiver's clock can follow. 10 min
   3. Asynchronous and Synchronous Transmission Send each byte with its own start and stop, or march whole blocks in lockstep — two ways to keep both ends in time. 4 min
   4. Multiplexing and Switching Techniques How do dozens of radio stations, calls and downloads share one link without tripping over each other? 5 min
   5. Unit 4 quiz4 questions on this unit 5 min
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   Unit 5 Full plan

   Error Detection and Correction

   Catching the wire's lies, because noise will flip bits and the trick is not to stop it but to notice.
   1. Types of Errors: Single-Bit and Burst Errors How the wire lies: one bit flipped, or a whole burst swept away by a single spike of noise. 3 min
   2. Redundancy, Error Detection and Error Correction To catch a lie, send a little extra truth along with the message. 4 min
   3. Parity Check: Simple and Two-Dimensional Parity Parity is a one-bit lie detector: it catches a flipped bit, but two flips at once slip straight past it. 4 min
   4. The Checksum Method The Internet checks its own packets with a clever bit of addition that wraps its carries around. 6 min
   5. Cyclic Redundancy Check (CRC) Ethernet and Wi-Fi trust a strange kind of division, with no carries at all, to catch almost every damaged frame. 5 min
   6. Detection and Correction of Burst Errors One flipped bit is easy to spot, but a burst of damage can fool every checker you've met — here's why. 9 min
   7. Unit 5 quiz7 questions on this unit 9 min
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   Unit 6 Full plan

   The Data Link Layer, Addressing and Network Security

   Who may speak on a shared wire, how every device is named — and how those names become a lock on the door.
   1. Sublayers of the Data Link Layer: LLC and MAC One layer, two halves: the LLC keeps each hop tidy while the MAC decides who may touch the wire. 3 min
   2. Media Access Control Protocols and Error Control On a shared Wi-Fi channel, who gets to talk next — and what happens when two devices speak at once? 9 min
   3. Levels of Addressing: Physical, Logical, Port and Specific Addresses Your message needs four names at once — for the next hop, the final machine, the right program and you. 9 min
   4. Using MAC Addresses to Protect a Private Network Every frame carries its sender's MAC address — so the address itself can become a lock on the door. 6 min
   5. Aspects of Network Security The pillars of network security: six guarantees every secure network has to keep, and the tools that keep them. 4 min
   6. Unit 6 quiz6 questions on this unit 8 min

Practise and remember