Lecture 4a: Communication and Networking

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Oct 23, 2013 (4 years and 21 days ago)

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Lecture 4a:
Communication
and Networking

CSCI102
-

Introduction to Information Technology B

ITCS905
-

Fundamentals of Information Technology

Overview

Network standards and
standardization bodies

The ISO 7
-
layer reference model in
general and its instantiation in
TCP/IP

Circuit switching and packet switching

Streams and datagrams

Overview

Physical layer networking concepts

Theoretical basis

Transmission media

Standards

Data link layer concepts

Framing

Error control

Flow control

Standards and Organisations
-

International:

ITU
-
T: International Telecommunications
Union
-

Telecommunications
Standardization Sector

Telephone and data communications

Formerly the CCITT

ITU
-
R: Radiocommunications Sector

Radio Frequencies

Formerly the CCIR

Standards and Organisations
-

International:

ISO
-

International Standards
Organisation for all communication
types

IETF


Internet Engineering Task
Force

Standards and Organisations
-

American

ANSI: American National Standards
Institute for data communications

EIA: Electrical Industries Association for
interfaces, connectors, facsimile, media

IEEE: Institute of Electrical and
Electronic Engineers specifically for 802
LAN standards

NIST: National Institute of Standards and
Technology the all American equivalent to
the ISO (of course!!)

The OSI Stack

Proposed by the International
Standards Organisation (ISO) and
other standards bodies

Its a layered approach to network
protocols involving encapsulation of
packets at each level of the stack and
the sub
-
layers

The OSI Stack


Transport

Data Link

Physical

Network

Session

Presentation

Application

7

6

5

4

3

2

1

The OSI Stack

End
-
to
-
end connections

Segments and reassembles
data in proper sequence

Setup and teardown of
“virtual circuits”
(connection oriented)

Can ensure segment
delivery with error
correction, recovery and
flow control

Transport

Data Link

Physical

Network

Session

Presentation

Application

7

6

5

4

3

2

1

The OSI Stack

Moves information to the
correct address

Assembles and disassembles
packets

Addresses and routes data
packets

Determines the best path
for moving data through the
network

Transport

Data Link

Physical

Network

Session

Presentation

Application

7

6

5

4

3

2

1

The OSI Stack

It is up to the data link
layer to detect and if
necessary correct errors

This is typically done by
breaking the bit stream
into distinct frames

Transport

Data Link

Physical

Network

Session

Presentation

Application

7

6

5

4

3

2

1

Data Link Layer Concepts

Methods of framing include

Character count

Start/end characters


character
stuffing

Start/end flags


bit stuffing

Physical layer coding violations

Data Link Layer Concepts

Error control

A noise burst on the line can destroy a frame
completely

Identified by

Acknowledgements

Timeouts

Individual packets can be retransmitted

Flow control

Throttles the sender to a rate that allows the
receiver to keep up and handle all traffic

The OSI Stack

The OSI physical layer is
concerned with the
transmission of bits on the
network

The order of bits

Bit level error
-
checking

Electrical / mechanical
characteristics

Transport

Data Link

Physical

Network

Session

Presentation

Application

7

6

5

4

3

2

1

Network Transmission Media

To be propagated (sent) from one
location to another, a signal must
travel along a physical path

The physical path that is used to
carry a signal between a signal
transmitter and a signal receiver is
called the "transmission medium"

Network Transmission Media

There are two types of transmission
media

Guided media

Unguided media

Network Transmission Media

There 4 basic types of guided media:

Open wire

Twisted pair

Coaxial cable

Optical Fibre

Unguided media

RF propagation

Microwave

Satellite

OSI
Instantiation in TCP/IP

Another widely used
reference model is the
TCP/IP model

Principles Used to Determine
Layers

Level of conception

Accurately defined duty

Internationally standardised
protocols

Minimal information flow across layer
boundaries

Number of layers