Erstellt von Julian Rottenberg
vor mehr als 6 Jahre
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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
Which communication types are showed here?
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