Transcript Introduction

Chapter One
Introduction to Computer
Networks and Data
Communications
1
Chapter One - Introduction to Computer
Networks And Data Communications
Introduction
• Who today has not used a computer network?
• Mass transit, interstate highways, 24-hour bankers,
grocery stores, cable television, cellphones,
businesses and schools, and retail outlets support
some form of computer network
2
Chapter One - Introduction to Computer
Networks And Data Communications
The Language of Computer Networks
• Computer network – an interconnection of computers
and computing equipment using either wires or radio
waves over small or large geographic areas
• Local area network – networks that are small in
geographic size spanning a room, floor, building, or
campus
3
Chapter One - Introduction to Computer
Networks And Data Communications
The Language of Computer Networks
• Metropolitan area network – networks that serve an
area of 1 to 30 miles, approximately the size of a
typical city
• Wide area network – a large network that
encompasses parts of states, multiple states, countries,
and the world
4
Chapter One - Introduction to Computer
Networks And Data Communications
The Language of Computer Networks
• Personal area network – a network of a few meters,
between wireless devices such as PDAs, laptops, and
similar devices
• Voice network – a network that transmits telephone
signals
• Data network – a network that transmits computer
data
5
Chapter One - Introduction to Computer
Networks And Data Communications
The Language of Computer Networks
• Data communications – the transfer of digital or
analog data using digital or analog signals
• Telecommunications – the study of telephones and
the systems that transmit telephone signals
• Network management – the design, installation, and
support of a network, including its hardware and
software
6
Chapter One - Introduction to Computer
Networks And Data Communications
The Big Picture
• Networks are composed of many devices, including:
–
–
–
–
–
Workstations (computers, telephones)
Servers
Network hubs and switches (bridges)
Routers (LAN to WAN and WAN to WAN)
Telephone switching gear
7
Chapter One - Introduction to Computer
Networks And Data Communications
8
Chapter One - Introduction to Computer
Networks And Data Communications
Computer Networks – Basic Connections
•
•
•
•
•
Computer terminal / microcomputer to mainframe
Microcomputer to local area network
Microcomputer to Internet
Local area network to local area network
Personal area network to workstation
9
Chapter One - Introduction to Computer
Networks And Data Communications
Computer Networks – Basic Connections
•
•
•
•
•
Local area network to metropolitan area network
Local area network to wide area network
Sensor to local area network
Satellite and microwave
Wireless telephone and wired telephone to network
10
Chapter One - Introduction to Computer
Networks And Data Communications
Basic Connections – Computer Terminal /
Microcomputer to Mainframe Computer
• Predominant form in the 1960s and 1970s
• Still used in many types of businesses for data entry
and data retrieval
• Usually involves a low-speed connection
11
Chapter One - Introduction to Computer
Networks And Data Communications
12
Chapter One - Introduction to Computer
Networks And Data Communications
Basic Connections – Microcomputer to
Local Area Network
• Highly common throughout business and academic
environments, and now homes
• Typically a medium- to high-speed connection
• Computer (device) requires a NIC (network interface
card)
• NIC connects to a hub-like device
13
Chapter One - Introduction to Computer
Networks And Data Communications
14
Chapter One - Introduction to Computer
Networks And Data Communications
Basic Connections – Microcomputer to
Internet
• Popular with home users and small businesses
• Often a dial-up modem is used to connect user’s
microcomputer to an Internet service provider
• Technologies such as DSL and cable modems are
replacing modems
15
Chapter One - Introduction to Computer
Networks And Data Communications
16
Chapter One - Introduction to Computer
Networks And Data Communications
Basic Connections – Local Area Network
to Local Area Network
• Found in systems that have two or more LANs and a
need for them to intercommunicate
• A bridge-like device (such as a switch) is typically
used to interconnect LANs
• Switch can filter frames
17
Chapter One - Introduction to Computer
Networks And Data Communications
18
Chapter One - Introduction to Computer
Networks And Data Communications
Basic Connections – Personal Area
Network to Workstation
• Interconnects wireless devices such as PDAs, laptops
and notebooks, and music playback devices
• Used over short distances such as a few meters
19
Chapter One - Introduction to Computer
Networks And Data Communications
20
Chapter One - Introduction to Computer
Networks And Data Communications
Basic Connections – Local Area Network
to Metropolitan Area Network
• Used to interconnect companies (usually their local
area networks) to networks that encompass a city
• High-speed networks with redundant circuits
• Metro Ethernet is latest form of metropolitan LAN
21
Chapter One - Introduction to Computer
Networks And Data Communications
22
Chapter One - Introduction to Computer
Networks And Data Communications
Basic Connections – Local Area Network
to Wide Area Network
• One of the most common ways to interconnect a user
on a LAN workstation to the Internet (a wide area
network)
• A router is the typical device that performs LAN to
WAN connections
• Routers are more complex devices than switches
23
Chapter One - Introduction to Computer
Networks And Data Communications
24
Chapter One - Introduction to Computer
Networks And Data Communications
Basic Connections – Wide Area Network to
Wide Area Network
• High-speed routers and switches are used to connect
one wide area network to another
• Thousands of wide area networks across North
America, many interconnected via these routers and
switches
25
Chapter One - Introduction to Computer
Networks And Data Communications
Basic Connections – Sensor to Local Area
Network
• Not all local area networks deal with microcomputer
workstations
• Often found in industrial and laboratory environments
• Assembly lines and robotic controls depend heavily
on sensor-based local area networks
26
Chapter One - Introduction to Computer
Networks And Data Communications
27
Chapter One - Introduction to Computer
Networks And Data Communications
Basic Connections – Satellite and
Microwave
• Typically long distance wireless connections
• Many types of applications including long distance
telephone, television, radio, long-haul data transfers,
and wireless data services
• Typically expensive services but many companies
offer competitive services and rates
• Newer shorter-distance services such as Wi-Max
28
Chapter One - Introduction to Computer
Networks And Data Communications
29
Chapter One - Introduction to Computer
Networks And Data Communications
Basic Connections – Wireless or Cellular
Telephones
• Constantly expanding market across the U.S. and
world
• Third generation services available in many areas and
under many types of plans
• Newest generation includes higher speed data
transfers (100s of kilobits per second)
30
Chapter One - Introduction to Computer
Networks And Data Communications
31
Chapter One - Introduction to Computer
Networks And Data Communications
An Additional Basic Connection –
Telephone to Network
• Telephone systems are ubiquitous and now carry
more data than voice
• Common configuration – telephone connected to
POTS
• Newer configuration (VoIP) – telephone to LAN via
gateway or telephone to gateway via DSL/cable
32
Chapter One - Introduction to Computer
Networks And Data Communications
Network Architectures
• A reference model that describes the layers of
hardware and software necessary to transmit data
between two points or for multiple devices /
applications to interoperate
• Reference models are necessary to increase likelihood
that different components from different
manufacturers will converse
• Two models to learn: OSI model and TCP/IP protocol
33
suite
Chapter One - Introduction to Computer
Networks And Data Communications
Network Architectures
• The OSI model’s seven layers:
34
Chapter One - Introduction to Computer
Networks And Data Communications
Network Architectures - OSI
• Application layer – where the application using the
network resides. Common network applications
include web browsing, e-mail, file transfers, and
remote logins
• Presentation layer – performs a series of
miscellaneous functions necessary for presenting the
data package properly to the sender or receiver
35
Chapter One - Introduction to Computer
Networks And Data Communications
Network Architectures - OSI
• Session layer – responsible for establishing sessions
between users
• Transport layer – provides an end-to-end error-free
network connection. Makes sure the data arrives at
the destination exactly as it left the source.
• Network layer – responsible for creating, maintaining
and ending network connections. Transfers a data
packet from node to node within the network.
36
Chapter One - Introduction to Computer
Networks And Data Communications
Network Architectures - OSI
• Data link layer – responsible for taking the data and
transforming it into a frame with header, control and
address information, and error detection code
• Physical layer – handles the transmission of bits over
a communications channel. Includes voltage levels,
connectors, media choice, modulation techniques
37
Chapter One - Introduction to Computer
Networks And Data Communications
38
Chapter One - Introduction to Computer
Networks And Data Communications
Network Architectures
• The TCP/IP protocol suite (DoD protocol suite, Internet
model):
39
Chapter One - Introduction to Computer
Networks And Data Communications
Network Architectures – TCP/IP
• Application layer – equivalent to OSI’s application
and presentation layers
• Transport layer – equivalent to OSI’s transport layer
• Network (Internet or internetwork) layer – equivalent
to OSI’s network layer
• Network access (data link/physical) layer –
equivalent to OSI’s data link and physical layers
40
Chapter One - Introduction to Computer
Networks And Data Communications
Network Architectures
• Logical and physical connections – A logical
connection is one that exists only in the software,
while a physical connection is one that exists in the
hardware
• Note that in a network architecture, only the lowest
layer contains the physical connection, while are
higher layers contain logical connections
41
Chapter One - Introduction to Computer
Networks And Data Communications
• Logical and physical connections
42
Chapter One - Introduction to Computer
Networks And Data Communications
• Example of data flow through layers
43
Chapter One - Introduction to Computer
Networks And Data Communications
• Network connections in action
44
Chapter One - Introduction to Computer
Networks And Data Communications
The TCP/IP protocol suite in action
• Note the flow of data from user to web browser and
back
• At each layer, information is either added or removed,
depending on whether the data is leaving or arriving
at a workstation
• The adding of information over pre-existing
information is termed encapsulation
45
Chapter One - Introduction to Computer
Networks And Data Communications
46