Data (universal)

Data (picture)

Information

(Data) Communication (original meaning)

(Data) Communication (universal meaning of "data")

(Data) Communication (literature and daily language definition)

(Data) Communication (definition of this class)

Data transport over Immaterial Carrier

Data transport over Material Carrier

Signal

Signal (picture)

Simplest Communication

Signal (short definition)

Immaterial Signals

What Good is a Physical Connection? - Signals
(picture)

What should be communicated?

What can be communicated between remote entities?

What do we need to make (data) communication possible?

What do transmitting signals from a physical carrier result in?

How long does it take for a signal to reach receiver?

How fast does a signal travel in the medium?

Formula for d (propagation delay)

Speed of electromagnetic waves in vacuum?

Speed of electromagnetic waves in copper?

Low-Level Properties of Communication (picture)

What happens in the first 'd' seconds after transmission starts?
Where are the bits?

Bandwidth / delay product (product of delay and data rate)

How Can a Wire Store Data? - Bandwidth-Delay Product

Two-way communication
(examples)

3 different communication types and what they are

How to Realize Half-Duplexing?
Which realization is better and what are their probelms?
1. Two pairs of cables, one for each direction
2. Use one cable

Realizing Half Duplex:
What can we do to fix this problem when using 1 cable intelligently?
- Both sending at the same time would not works, signals interfere. How can one node decide that the other is done sending?

How to realize Full-Duplexing?

TO BE DONE: Quick Tour page 18
How to realize duplexing - full duplex by time divison duplexing

Advantages of circuit switching

disadvantages of circuit switching

packet switching:

packets

Problems with packets

packets (picture)

Switch (and problems)

Packet Switching:
Switches additional tasks?

packet switching (advantages / disadvantages)

packet switching (picture)

Multiplexing

Multiplexing
Options for sending

Multiplexing:
other options

Multiplexing:
parallels / relations to duplex operation

The prupose of multiplexing

concept of virtualizing and enriching properties of a simpler subsystem

Multiplexing & Shared Resources

examples of shared Resources

virtually shared vs shared

common characteristics of a broadcast medium

Problem of multiple access to a shared medium

options for Next Hop Selection

Routing tables

Source of errors / abnormal situations

error control

congestion control

flow control

overload control

Where and how to implement error and overload control

Layers

SAP

Services (layers)

Service

Layers and Services

Layers and Services (Bild)

Service Primitives

Bit Transmission Layer (Example)

Main Groups (Service Primitives)

4 Main Types / Groups - Service Primitives

two main possibilities how to treat data in service primitive design

Unit of data are well-delimited messages
(Service Primitives - Unit of Data)

Unit of data is individual byte, sequence of bytes or byte stream is transmitted
(Service Primitives - Unit of Data)

Correctness Requirements

Connection-oriented service

Connection-less service

Connection-Oriented vs Connection-Less Service

Connection-Oriented Primitives to handle connection

Typical Examples of Services

Datagram service

Reliable byte stream

A Concrete Service Interface - BSD Sockets

Datagram Communication Over Sockets (Bild / komplette Folie)

Byte Streams Over a Connection-Oriented Socket (Bild / komplette Folie)

What's a Protocol?

Human Protocol vs Network Protocol

Layers are Distributed

Distributed Layers Need to Follow Rules - Protocols

Protocols

Protocols - peer protocol entities / peers

Protocols (Bild)

Service and Protocol (Bild)

Protocol Specification

Protocol Specification - FSM

Protocols and FSMs

Protocols and FSMs (Bild)

Protocols and FSMs
- Communication Finite state machines to remote peer

Protocols and Messages

Protocols and Messages (Bild)

Protocol Stacks

Protocol Stacks
- Strict layering

Protocol Stacking (Bild)

Layers do not Care About Distributed Lower Layers

Layers do not Care About Distributed Lower Layers (Bild)

Protocol Mechanisms: What Do Protocols Do for a Living?
- Addressing/naming
- Fragmentation
- Re-Sequencing

Protocol Mechanisms: What Do Protocols Do for a Living?
- Error control
- Flow Control
- Congestion control

Protocol Mechanisms: What Do Protocols Do for a Living?
- Resource allocation
- Multiplexing

Protocol Mechanisms: What Do Protocols Do for a Living?
- Compression
- Privacy, authentication

How to Structure Functions / Layers in Real Systems?

How to actually group Functions / Layers so as to obtain a real, working communication system?

Layered Communication System (Bild)

Layering Considered Harmful?
-> Benefits of layering

Layering Considered Harmful?
- Problems / Disadvantages of layering

Layering Considered Harmful?
- Main reference models

ISO/OSI Reference Model
- Basic design principles

ISO/OSI Reference Model
- 7-layer model

ISO/OSI 7-Layer Reference Model (two entities)
(Bild)

ISO/OSI 7-Layer Reference Model (complete network)
(Bild)

OSI Layers
- Physical Layer (PH)

OSI Layers
- Link Layer (L)

OSI Layers
- Network Layer (N)

OSI Layers
- Transport Layer (T)

OSI Layers
- Session Layer (S)

OSI Layers
- Presentation Layer (P)

OSI Layers
- Application Layer (A)

ISO/OSI Reference Model - Critique

Architectural Requirements of the Internet

Architectural Requirements of the Internet
- Generality

Architectural Requirement of the Internet
- Heterogeneity

Architectural Requirements of the Internet
- Robustness / Extensibility

Architectural Requirements of the Internet
- Scalability

Towards the End-to-End Principle

Towards the End-to-End Principle
- Dumb network: require only least common service

Towards the End-to-End Principle
- Smart hosts

TCP/IP Reference Model
- Internet Layer

TCP/IP Reference Model
- Transport Layer

TCP/IP Protocol Stack

Protocol Layering and Data in the Internet

Protocol Layering and Data in the Internet
(Bild)

TCP/IP Suite of Protocols

TCP/IP Suite of Protocols
(Bild)

ARPANet: Protocols and Stack

ARPANet: Protocols and Stack

TCP/IP Reference Model - Critique

ISO/OSI versus TCP/IP

Standardization

Basic Service of Physical Layer: Transport Bits

Basic Service of Physical Layer: Transport Bits

A Bit-to-Signal Conversion Rule

Example: Transmit Bit Pattern for Character "b"

What Arrives at the Receiver?

Some Background: Fourier Analysis

Fourier Analysis - Computing Coefficients

Applying Fourier Analysis to the Example
(1)

Applying Fourier Analysis to the Example
(2)

Fact 1: Signals are Attenuated in a Phsical Medium

Fact 2: Not all Frequencies Pass Through a Medium

Bandwidth-Limited Medium - Example

Fact 3: Attenuation Depends on Frequency

Example with Frequency-Dependent Attenuation

Fact 4: Media does not only Attenuate, but also Distorts

Example with Frequency-Dependent Attenuation and Jitter

Fact 5: Real Media are Noisy

Example w/ Frequency-Dependent Attenuation, Jitter & Random Noise

Converting Signals to Data: Sampling

Sampling Over a Noisy or Bandwidth-Limited Channel

Sampling & Low Bandwidth

Possible Way Out: Make Thresholds Wider?

Way Out 2: Increase Time for a Single Bit

Way Out 3: Use More Than Just 0 and 1 in the Channel

Way Out 3: Use Four-Level Symbols to Encode Two Bits

Data Rate with Multi-Valued Symbols - Nyquist

Unlimited Data Rate with Many Symbol Levels?

Shannon Limit on Achievable Data Rate

When to Sample the Received Signal?
- How does the receiver know WHEN to check the received signal for its value?

When to Sample the Received Signal?

Overly Simplistic Bit Sychronization

Options to Tell the Receiver when to Sample
(1 - Clock)

Options to Tell the Reciver When to Sample
(2 - Points)

Options to Tell the Receiver When to Sample
(3 - extract)

Extract Clock Information from Signal Itself - NRZ-L

Extract Clock Information from Signal Itself - Manchester

Baseband versus Broadband Transmission
(Baseband transmission)

Baseband versus Broadband Transmission
(Baseband transmission - Problems)

Boardband Transmission

Amplitude Modulation

Amplitude Modulation - Example

Frequency Modulation

Phase Modulation

Phase Modulation With High Multiple Values per Symbol

Combinations of Different Modulations

Interlude: Digital vs Analog Signals

Electromagnetic Spectrum and Media