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Introduction
Chapter 1
Panko’s
Business Data Networks and Telecommunications, 5th edition
Copyright 2005 Prentice-Hall
Learning Objectives

By the end of this session, you should be able
to

List the eight elements of networks.

Explain the major types of networks in businesses:
LANs, WANs, internets, intranets, and extranets.

Discuss major concerns for network managers:
staffing, network architecture, standards, security,
wireless networking, efficiency, and quality of service
(QoS).

Explain the elements and operation of a small home
PC network using a LAN
2
Definition

A NETWORK is a system of hardware software
and transmission components that allow
applications to on different stations within the
system communicate with each other
3
Figure 1-2: Elements of a Network
Message (Frame)
Application
Application
Client
Station
Switch
Server
Station
Switch
Access
Line
Switch
Mobile Client
Station
Trunk
Line
Trunk
Line
Switch
Outside
World
Router
Mobile Client
Station
lines
connect
stations
toThe
switches
Switches
move
frames
to or closer
to different
the
destination
station
Stations (and
routers)Access
usually
communicate
path
a frame
takes
Networks
connect
applications
on
stations.
Routers
connect
networks
to
the
outside
world.
Treated
just
like
stations
Networks
connect
stations:
clients
(fixed
and
mobile)
and
servers
lines
connect
switches
to switches
(and
routers)
Switches
packet
sequentially
by sendingTrunk
messages
called handle
frames
is
called
its data link
Applications
are
alla users
care
about
4
Figures 1-6 and 1-7: Workgroup and Core
Switches
19 inches (48 cm) wide
19 inches (48 cm) wide
Small Switches
(Stacked):
Workgroup Switches
To Link Stations
To Network
Central Core Switch
5
Figure 1-3: Multiplexing in a Packet-Switched
Network
Trunk line
multiplexes the
messages of
different
conversations
AC
Client
Station A
AC
AC BD
BD
Mobile Client
Station B
AC
AC
Trunk Line
Access
Line
AC
This reduces
trunk line
costs through
cost sharing
by users
Server
Station C
BD
BD
Router D
6
Figure 1-2: Elements of a Network (Recap)

Applications (the only element that users care about)

Stations


Clients
Servers

Switches

Routers

Transmission Lines



Trunk lines
Access Lines
Messages (Frames)
Never talk about an
Innovation “reducing cost,”
“increasing speed,” etc.
without specifying
which element is
cheaper or faster.
For example, multiplexing
only reduces the cost of
trunk lines; other
costs are not decreased
7
LANs and WANs

LANs transmit data
within corporate sites

WANs transmit data
between corporate sites

Each LAN or WAN is a
single network
WAN
8
Figure 1-5: Local Area Network (LAN) in a
Large Building
Multi-floor
Office Building
The bank has multiple
LANs—one at each site
9
Figure 1-5: Local Area Network (LAN) in a Large
Building, Continued
Wall Jack
Workgroup Switch
Workgroup Switch
To
WAN
Router
Core Switch
10
Internets

Most firms have multiple LANs and WANs.

They must create internets

An internet is a collection of networks connected by
routers so that any application on any host on any
single network can communicate with any
application on any other host on any other network
in the internet.
Application
Application
LAN
WAN
Router
LAN
Router
11
Figure 1-8: Internet with Three Networks
Host A
R1
Packet
Network X
Network Z
A packet goes all the
way across the internet;
It’s path is its route
Network Y
Route A-B
R2
Host B
12
Figure 1-8: Internet with Three Networks,
Continued

Messages in single networks (LANs or WANs) are
called frames

Message in internets are called packets


Travel from the source host to the destination host
across the entire internet
Within a single network, the packet is encapsulated in
(carried in) the network’s frame
Packet
Package
(Packet)
Truck
(frame)
Frame
13
Figure 1-8: Internet with Three Networks,
Continued
Frame X
Details in
Network X
Packet
Data Link
A-R1
Switch
Host A
Switch
Server
Host
Switch
X1
Mobile Client
Host
Switch
X2
Route
A-B
Router R1
Network X
14
Figure 1-8: Internet with Three Networks,
Continued
Details in
Network Y
To
Network X
Route
A-B
Router R1
Data Link
R1-R2
To
Network Z
Router R2
Frame Y
Packet
Network Y
15
Figure 1-8: Internet with Three Networks,
Continued
Data Link
R2-B
Details in
Network Z
Packet
Frame Z
Switch
Z1
Host B
Switch
Router R2
Switch
Z2
Mobile Client
Hosts
Switch
Router
Network Z
16
Figure 1-8: Internet with Three Networks,
Continued

In this internet with three networks, in a
transmission,



There is one packet
There are three frames (one in each network)
If a packet in an internet must pass through N
networks,


How many packets will be sent?
How many frames must carry the packet?
17
Figure 1-8: Internet with Three Networks,
Continued

Lower-case internet is any internet

Upper-case Internet is the global Internet
18
Figure 1-11: The Internet
Webserver
User PC
Access
Line
The Internet Backbone
(Multiple Carriers)
Access
Line
Router
NAP
ISP 2 NAP
NAP
ISP 1
ISP 4
ISP 3
Internet
Service
Provider
For User PC
NAP = Network Access Point
Internet Service
Provider
For Webserver
19
Figures 1-9 and 1-10: Routers
19 inches (48 cm) wide
19 inches (48 cm) wide
Small Routers
Stacked
For Branch Offices
Large Routers
for Large Sites and ISPs
20
Figure 1-12: The Internet, internets,
Intranets, and Extranets

internets versus the Internet

Intranets


Internal internet for use within an organization

Based on the TCP/IP standards created for the
Internet
Extranets

Connect multiple firms
 Only some computers from each firm are on the
extranet

Use TCP/IP standards
21
Recap


Switches versus Routers

Switches move frames through single networks
(LANs or WANs)

Routers move packets through internets
Messages

Messages in single networks are called frames

Messages in internets are called packets

Packets are encapsulated within frames
22
End Day 1
23
Day 2
24

Review

List the 8 common elements of a network

Explain difference between a message and a packet

Explain difference between switch and router

Difference between trunk and access lines

Given an internet, indicate number of frames,
packets, networks traversed for message from A to B

Different types of addresses
25
Figure 1-23: Logical Functions of the
Access Router
Cable
Modem
Access Router
Router Function
DHCP
Server
Function
NAT
Function
Switch Function
26
Figure 1-24: Ethernet Switch Operation
Switching Table
Port Host
10
A1-44-D5-1F-AA-4C
13
B2-CD-13-5B-E4-65
15
C3-2D-55-3B-A9-4F
16
D4-47-55-C4-B6-9F
Ethernet Switch
UTP
UTP
Frame To C3…
A1-44-D5-1F-AA-4C
UTP
UTP
D4-47-55-C4-B6-9F
Frame To C3…
C3-2D-55-3B-A9-4F
B2-CD-13-5B-E4-65
27
Figure 1-25: Frames and Packets
Cable
Modem
Packet in
DOCIS
Frame
Internal
Router
Access Router
Packet is always
carried (encapsulated)
in a frame
A1-BD-33-6E-C7-BB
IP address = 192.168.0.3
PC in Emily’s Room
Packet in
Ethernet Frame
B2-CD-13-5B-E4-65
IP address = 192.168.0.2
PC in Study
28
Figure 1-26: Dynamic Host Configuration
Protocol (DHCP)
Cable
Modem
ISP
DHCP
Server
1.
IP Address =
60.47.112.6
Access Router
A1-BD-33-6E-C7-BB
PC in Emily’s Room
The ISP only
Gives each home a
Single IP address B2-CD-13-5B-E4-65
PC in Study
A DHCP Server
provides User PCs with
a temporary IP Address
each time the user
connects to the Internet
29
Figure 1-26: Dynamic Host Configuration
Protocol (DHCP), Continued
Cable
Modem
ISP
DHCP
Server
1.
IP Address =
60.47.112.6
Internal
DHCP
Server
Access Router
A1-BD-33-6E-C7-BB
IP address = 192.168.0.3
PC in Emily’s Room
2. IP Address =
192.168.0.3
2. IP Address =
192.168.0.2
The access router’s
Internal DHCP server
Gives private IP
Addresses to each PC
B2-CD-13-5B-E4-65
IP address = 192.168.0.2
PC in Study
30
Figure 1-27: Network Address Translation
(NAT)
2. Packet from
60.47.112.6
Webserver
IP address=
123.7.86.285
Cable
Modem
Internal
NAT
Module
Access Router
The access router’s NAT
module translates between the
private IP addresses and
the single ISP-given IP address
1. Packet from
192.168.0.2
PC in Study
192.168.0.2
31
Figure 1-27: Network Address Translation
(NAT), Continued
3.
Packet
to
60.47.112.6
Webserver
IP address=
123.7.86.285
Cable
Modem
Internal
NAT
Module
Access Router
4. Packet to
192.168.0.2
PC in Study
192.168.0.2
32
Figure 1-28: The Domain Name System
(DNS), Continued
DNS Table
Originating
Host’s DNS
Resolver
Host Name
…
…
Voyager.cba.hawaii.edu
…
IP Address
…
…
128.171.17.13
…
DNS Request Message
“The host name is Voyager.cba.hawaii.edu”
DNS Response Message
“The IP address is 128.171.17.13”
DNS
Host
33
Figure 1-29: Converting Binary IP Addresses to
Dotted Decimal Notation
Binary
IP Address
01111111101010110001000100001101
8-Bit
Segments
01111111 10101011 00010001 00001101
Convert
Segments
to Decimal
Dotted
Decimal
Notation
127
171
17
13
127.171.17.13
34
Elements of a Network
Message (Frame)
Application
Application
Client
Station
Switch
Server
Station
Switch
Access
Line
Switch
Mobile Client
Station
Trunk
Line
Switch
Trunk
Line
Outside
World
Router
Mobile Client
Station
35
Figure 1-22: Home Network Access Router
About 4 inches (10 cm) Wide
Power
Jack for
External
Power
Switch Ports
UTP Cords
Run to Stations
WAN Port
UTP Cord
Runs to
Cable Modem
36
Figure 1-19: Network Interface Cards
(NICs) (Photo)
Internal NIC. Installed inside
systems unit. Plugged into
expansion slot on the mother
board.
PC Card NIC. Installed in PC
Card slot in notebook and some
PDAs.
37
Internal NIC
RJ-45
Jack
PCI Connector Pins
38
Computer Mother Board

Mother Board
PCI Slots
for Expansion Boards
(NICs, etc.)
Slots for RAM
Slot for
Microprocessor
(Pentium 4)
39
Mother Board and Expansion Boards
Expansion Board
(NIC)
Connector
Expansion
Slots
Mother Board
40
Figure 1-20: Unshielded Twisted Pair
(UTP) Cord With RJ-45 Connector (Photo)
4-Pair Unshielded Twisted Pair (UTP)
Industry Standard Pen
8-Pin RJ-45 Connector
UTP Cord
41
Figure 1-21: UTP Cord RJ-45 Connector and
Jack
UTP Cord
--About as thick
as a pencil
--Rugged and
Flexible
RJ-45 Jack
On a Wall
On a Switch
or
On a NIC
RJ-45
Connector
42
Figure 1-13: Major Network Technical Concerns

Architecture

Standards

Security

Efficiency

Wireless Communication

QoS
43
Figure 1-13: Major Network Technical
Concerns

Network Architecture
 A broad plan for how the firm will connect all of its computers
within buildings (local area networks), between sites (wide area
networks), and to the Internet

New systems must fit the rules of the architecture

Scalability – ability to accommodate growth efficiently

Undisciplined growth in the past
 No overall plan
Legacy networks


Use obsolete technologies that do not fit the long-term
architecture

Too expensive to replace quickly; must live with many for
awhile
44
Figure 1-13: Major Network Technical
Concerns, Continued

Standards

Standards govern message interactions between pairs of
entities (Figure 1-14)


For example, HTTP request and response messages for WWW
access
Standards create competition

This reduces costs

It also stimulates the development of new features

Protects the business if the main vendors go out of
business
45
Figure 1-13: Major Network Technical
Concerns, Continued

Security

A Major Problem

Many attacks

Growing trend toward
criminal attackers
46
Figure 1-15: Firewalls
Allowed Legitimate Border
Packet
Firewall
Attacker
Hardened
Server
Hardened
Client PC
Border firewall
should pass
legitimate packets
Log File
Legitimate
Packet
Legitimate
Host
Internal
Corporate
Network
47
Figure 1-15: Firewalls, Continued
Border firewall
should deny (drop)
Hardened and log
Server attack packets
Hardened
Client PC
Border
Firewall
Attack Packet
Denied
Attack
Packet
Log File
Network Management
Console
Attacker
Legitimate
Host
Internal
Corporate
Network
48
Figure 1-13: Major Network Technical
Concerns, Continued

Security

Virtual Private Networks (VPNs) (Figure 1-16)

Provide communication over the Internet with
added security

Cryptographic protection for confidentiality
(eavesdroppers cannot read)

Cryptographic authentication (confirms sender’s
identity)
49
Figure 1-16: Virtual Private Networks
(VPNs)
Site-to-Site VPN
Using Gateway
Client
VPN
Remote Access
Gateway PC 1
VPN Using
Corporate
Gateway
Site B
VPN
Gateway
Internal
Server
Corporate
Site A
Internet
Host-to-Host
VPN
Remote
Client PC 2
Remote Client PC 3
50
Figure 1-13: Major Network Management
Concerns, Continued

Wireless
Communication

To improve mobility

Drive-by hackers can
eavesdrop on internal
communication

Drive-by hackers can
break into the network
bypassing firewalls
Drive-By Hacker
51
Figure 1-13: Major Network Technical
Concerns, Continued

Quality of Service (QoS)
QoS

Numerical objectives for performance

Transmission speed in bits per second (bps)



A bit is a single one or zero
NOT bytes per second
Increase by factors of 1000, not 1024
 kilobits per second (kbps)—lower-case k
 Megabits per second (Mbps)
 Gigabits per second (Gbps)
 Terabits per second (Tbps)
52
Figure 1-13: Major Network Technical
Concerns, Continued

Quality of Service




For Transmission Speed, have 1 to 3 places
BEFORE the decimal point.
Example
 .5 Mbps is wrong
 500 kbps is correct
Example
 2,300 Mbps is wrong
 2.3 Gbps is correct
Example
 473.2 Mbps is correct
53
Figure 1-13: Major Network Technical
Concerns, Continued

Quality of Service

Typical transmission speeds in
most firms:

LANs: 100 Mbps to each
desktop

WANs: most site-to-site links
only are 56 kbps to a few
megabits per second because
long-distance transmission is
very expensive and so must
be used more sparingly
LANs:
100 Mbps
WANs:
56 kbps
to a few
Mbps
54
Figure 1-13: Major Network Technical
Concerns, Continued

Quality of Service

Congestion, Throughput, Latency, and
Response Time

Congestion: when there is too much traffic for
the network’s capacity

Throughput: The speed users actually see
(often much less than rated speed)

Individual throughput is less than total
throughput on shared-speed links
55
Figure 1-13: Major Network Technical
Concerns, Continued

Quality of Service

Congestion, Throughput,
Latency, and Response Time
 Latency: delay (usually
measured in milliseconds or
ms)

Within corporations, latency is
typically under 60 ms 90% of
the time

On the Internet, typically 30
ms to 150 ms
56
Figure 1-13: Major Network Technical
Concerns, Continued

Quality of Service

Congestion, Throughput, Latency, and Response
Time
 Response Time

The time to get a response after a user
issues a command

A quarter second
or less is good
57
Figure 1-13: Major Network Technical
Concerns, Continued

Availability

Availability is the percentage of
time a network can be used

Downtime: when the user cannot use the network

Want 24x7 availability

Telephone network gives 99.999% availability

Typical networks reach 98% today
58
Figure 1-13: Major Network Technical
Concerns, Continued

Error Rate

Measured as the percentage of messages
damaged or lost

Substantial error rates can disrupt applications

Substantial error rates generate more network
traffic because of retransmissions
59