How is Information Transferred?

Developing an Intuition for Network Communication Protocols

a 6.UAT concept talk by

Olga Stroilova

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Information transfer networks are everywhere

Internet connection: Ethernet

Laptop WiFi: Wireless LAN

Cell phones: Mobile network

How do these systems work?

• Read the lengthy (and complicated) 802 IEEE standard• Build up an intuition by trying to design them yourself!

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What is Information and how do I Transfer It?

Real life:

Sounds, letters, signs, pictures, movies

Digital world:

0’s and 1’s, voltage high and lows, radio waves

Methods of Information Transfer

Speech, Morse code, wire and radio communication

Rules of transfer are called Communication Protocols

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Ethernet

Idea Cut down costs by connecting all computers with a single wire

Communication Protocol• Listen to the wire and transmit if it is free• Monitor wire during transmission• If interference is detected, stop, wait and try again

“Play Nice”: Randomized Backoff + Collision Detection

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Wireless Local Area Network

Idea Use radio waves as transfer medium for increased portability

Communication Protocol• Divide 2.4 GHz radio wave band into channels• Assign several transmissions to each channel• Cannot detect collisions, so acknowledge each message

“Play First, Check Later”: Randomized Backoff + Collision Avoidance

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Mobile Phone Network

Idea Ensure quality of data stream by reducing probability of collision

Communication Protocol• Put up towers to divide area into cells• Divide company frequency bandwidth into channels• Allot one transmission per channel per cell

“Play By Yourself”: No Collisions, No Backoff

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In Conclusion …

Protocols are designed based on the

product goals, limitations, and tradeoffs.

To understand how they work, Think like an Engineer!

Ethernet

Cellular Wireless