Communication

Communication
An Introduction

Prof. David Bernstein
James Madison University

Computer Science Department

bernstdh@jmu.edu

About the Word "Communication"

Etymology:
- From the Latin communis meaning to share
Defined:
- The transmission or exchange of information, knowledge, or ideas, by means of speech, writing, mechanical or electronic media, etc.;

Some Kinds of Communication

Models of Communication

Shannon and Weaver, 1949 (Bell Laboratories):
- Information source produces a message
- Transmitter encodes the message into signals
- Channel carries the signals
- Receiver decodes the message from the signal
- Destination receives the message
Berlo, 1960:
- Sender issues - skills, attitude, knowledge, culture
- Message issues - content, elements, treatment, structure, codes
- Channel issues - hearing, seeing, touching, tasting, feeling
- Receiver issues - skills, attitude, kowledge, culture

The Focus of Computer Scientists and Engineers

"Hard" Technologies:
- Transmission Equipment
- Transmission Media
- Sending/Receiving Devices
"Soft" Technologies:
- Protocols
- Algorithms
- Software

Communication Networks

Physical Communication Networks

Some Obervations:
- Every source-destination pair may not be directly connected
- As a result, intermediaries may need to be involved
- Hence, switching is required
Types of Switching:
- Circuit Switching (i.e., reserved resources)
- Packet Switching (i.e., resources on demand)

Properties/Issues to Consider

Delay/Timeliness
- Processing Delay
- Queueing Delay
- Transmission Delay
- Propagation Delay
Capacity/Bandwidth
Reliability
Simplex, Half-Duplex, Full-Duplex
Asynchronous, Synchronous
- Low-Level: Whether a timing signal is used
- High-Level: Whether both/all parties are involved simultaneously
Architecture
- Client-Server
- Peer-to-Peer