overview of data communications and networking

expanded by Jozef GoetzMcGraw-Hill ©The McGraw-Hill Companies, Inc., 2004

Overview of Overview of Data Communications Data Communications

and and NetworkingNetworking

PART IPART I


Overview


Chapters

Chapter 1 Introduction

Chapter 2 Network Models


Chapter 1

Introduction


1.1 Data Communication

•Data communication is the transfer of data from one device to another via some form of transmission medium.

•A data communications system must transmit data to the correct destination in an accurate and timely manner.

•Components

•Data Representation

•Direction of Data Flow


Figure 1.1 Five components of data communication

are the message, sender, receiver, medium, and protocol.


Data Representation text, numbers, images, audio, and video are different forms of information.


Figure 1.2 Simplexe.g. the keyboard and the monitor

Direction of Data Flow


Figure 1.3 Half-duplexe.g. Walkie-talkies, CB radios


Figure 1.4 Full-duplex

e.g. 2 people are communicating by a tel. line


A network is a set of communication devices connected by media links.

1.2 Networks


1.2 Networks

1.Distributed Processing• Task is divided

2.Network Criteria• Important: performance,

reliability, security

3.Physical Structures

4.Categories of Networks


Figure 1.5 Point-to-point connection

Physical Structures

3. Physical Structures

In a point-to-point connection, two and only two devices are connected by a dedicated link.


Figure 1.6 Multipoint connection (timeshare connection – capacity)

In a multipoint connection, three or more devices share a link.


1.2 NETWORKS How do we categorize?

Topology, geography Technology

Geographic Wide area networks Metropolitan networks Local area networks Personal networks

Technologies Circuit switched Packet switched


Figure 1.7 Categories of topology (a network is layout physically)

A topology is the geometric representation of the relationship of all the links and linking devices

4. Categories of Networks


Figure 1.8 Fully connected mesh topology (for five devices)

Every device has a dedicated point to point link to every other device


Figure 1.9 Star topology

Each device has a dedicated point to point link only to a central controller, called a hub

If one device wants to send data to another. •It sends the data to the controller, which then relays the data to the other connected device.


Figure 1.10 Bus topology is multipoint, previous all were point to point

connector

connection

One long cable acts as a backbone


Figure 1.11 Ring topology

Each device has a dedicated point to point link only with 2 devices on either side of it.

When a device receives a signal intended for another device, its repeater regenerates the bits and passes them along.


Figure 1.12 Categories of networks

A network falls is determined by criteria:1. Its size2. Its ownership3. The distance


Figure 1.13 LAN - Local Area Network

•Designed for a single office, campus, building or between nearby buildings. •LANs allow resources to be shared

•Hardware•Software•Data

between PCs or workstations.•License restriction


Figure 1.13 LAN (Continued)

A given LAN use only one type of transmission medium.

Speed : 4-16 MbpsToday: 100 Mbps


Figure 1.14 MAN Metropolitan Area Network (e.g. cable TV)

Designed to extend over an entire city, connects LANs

LANs can be shared

- offices can be connected via a city


Figure 1.15 WAN - Wide Area Network

Provides all transmission (data, video, image etc.) over large areas e.g. states, countries, a continent , or the whole world.

In contrast to LANs may utilize public, leased, or private communication equipment.


EO - End OfficePSTN – Public Switching Telephony NetworkPBX – Private Exchange Switch


1.3 The Internet1.3 The Internet

•A Brief History•The Internet Today

•When 2 or more networks are connected, they become an internetwork, or internet.

•An internet is a network of networks.

•The Internet (upper case) is a collaboration of more than 100s thousands interconnected networks.

•The Internet is a structured, organized collection of many separate networks.

•TCP/IP is the protocol suite for the Internet.


Figure 1.16 Internet today

NAP = Network Access Point is the complex switching stations.Speed: up to 600 Mbps

•End users to be connected use the services of Internet Service Provider (ISP)

There are local, regional, national, and international Internet service providers (ISPs).


Figure 1.16 Internet today

NAP = Network Access PointUp to 600 Mbps


1.4 Protocols and Standards1.4 Protocols and Standards

•Protocols •Set of rules that governs data communication•Key elements:

•Syntax•Structure or format – order in which they are presented

•Semantics•Meaning of each section of bits

•Timing•What data and how fast they can be sent


A standard provides a model for development that enables a product to work regardless of the individual manufacturer

Standards are essential in: i. Creating competitive markets for

equipment manufacturers ii. Guaranteeing national and

international interoperability and compatibility

1.4 Standards1.4 Standards


De Facto (by fact) standards Proprietary Nonproprietary

De Jure (by law) standards

1.4 Standards Categories1.4 Standards Categories


Standards Organizations The ISO, ITU-T (previously CCITT), ANSI, IEEE, and EIA

are some of the organizations involved in standards creation.



Forum Consist of representatives from

interested corporations Present their conclusions to the standards

bodies Facilitate standardization process

Frame Relay Forum ATM Forum and Consortium Internet Society (ISOC) and Internet Engineering Task Force (IETF)



Forum are special-interest groups (work

with universities and users), that evaluate and standardize new technologies.

Internet Standards A Request for Comment (RFC) is an

idea or concept that is a precursor to an Internet standard.



ISO (International Standards Organization) 1946 – vast number of subjects

89 countries 13000 standards ISO is a member of ITU-T Documents are:

Draft Draft International International Standard

ANSI (American National Standards Institute) Private, nongovernmental, nonprofit organization

NIST (National Institute of Standards and Technology) – a part of the US Dept of Commerce

IEEE (Institute of Electrical and Electronics Engineering)

Largest professional organization in the world ITU-T International Telecommunications Union -

Telecommunications Standardization Sector (former CCITT) – 3000 recommendations



ISO ISO 8877—Interface in Integrated

Services Digital Network (ISDN) ISO 3309—HDLC frame structure ISO 8028—X.25 packet level protocol



ITU-T V.32: Defines data transmission over

phone lines X.25: Defines transmission over public

digital networks I.430: Define physical layer

specifications for an interface



ANSI X3. 23-1985 Programming language

COBOL SONET Synchronous Optical Network ISDN Integrated Services Digital

Network



IEEE IEEE 802.3: CSMA/CD LAN IEEE 802.4: Token Bus LAN IEEE 802.5: Token Ring LAN



EIA EIA-232: A 25-pin interface standard EIA-449: Specifies a 37-pin connector

and a 9-pin connector EIA-530: Defines a 25-pin connector



Federal Communication Commission (FCC)

Authority for interstate and international traffic Reviews communication services and prices Reviews technical specs of communication

hardware Assigns carrier frequencies for radio and

television

Public Utility Commission Authority for intrastate traffic

1.4 Regulatory Agencies1.4 Regulatory Agencies