1. Introduction
Chapter 1
Panko’s Business Data Networks and Telecommunications, 5th edition Copyright 2005 Prentice-Hall

2. 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

3. 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

4. Figure 1-2: Elements of a Network
Client
Station
Mobile Client
Application
Message (Frame)
Server
Station
Switch
Access
Line
Trunk
Line
Outside
World
Router
Access lines connect stations to switches
Trunk lines connect switches to switches (and routers)
Networks connect stations: clients (fixed and mobile) and servers
Stations (and routers) usually communicate
by sending messages called frames
The path a frame takes
is called its data link
Switches move frames to or closer to the destination station
Switches handle a packet sequentially
Routers connect networks to the outside world. Treated just like stations
Networks connect applications on different stations.
Applications are all users care about

5. 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

6. Figure 1-3: Multiplexing in a Packet-Switched Network
Trunk line
multiplexes the
messages of
different
conversations AC AC
Client
Station A AC
Server
Station C AC AC BD AC
Trunk Line
This reduces
trunk line
costs through
cost sharing
by users BD
Access
Line BD BD
Router D
Mobile Client
Station B

7. 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

8. LANs and WANs LANs transmit data within corporate sites
WANs transmit data between corporate sites
Each LAN or WAN is a single network

9. Figure 1-5: Local Area Network (LAN) in a Large Building
Multi-floor
Office Building
The bank has multiple
LANs—one at each site

10. Figure 1-5: Local Area Network (LAN) in a Large Building, Continued
Wall Jack
Workgroup Switch
Workgroup Switch To
WAN
Core Switch
Router

11. 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
LAN
Router
Router

12. Figure 1-8: Internet with Three Networks
Host A R1
Packet
Network X
A packet goes all the
way across the internet;
It’s path is its route
Network Y
Route A-B
Network Z R2
Host B

13. 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
Package
(Packet)
Truck
(frame)
Packet
Frame

14. 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

15. Figure 1-8: Internet with Three Networks, Continued
Details in
Network Y To
Network X
Route
A-B
Router R1
Frame Y
Data Link
R1-R2
Packet To
Network Z
Router R2
Network Y

16. Figure 1-8: Internet with Three Networks, Continued
Details in
Network Z
Packet
Data Link
R2-B
Frame Z
Switch Z1
Host B
Switch
Router R2
Switch Z2
Mobile Client
Hosts
Switch
Router
Network Z

17. 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?

18. Figure 1-8: Internet with Three Networks, Continued
Lower-case internet is any internet
Upper-case Internet is the global Internet

19. NAP = Network Access Point
Figure 1-11: The Internet
Webserver
User PC
The Internet Backbone
(Multiple Carriers)
Access
Line
Access
Line
Router
NAP
NAP
ISP 2
NAP
ISP 4
ISP 1
ISP 3
Internet
Service
Provider
For User PC
Internet Service
Provider
For Webserver
NAP = Network Access Point

20. 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

21. 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

22. Recap Switches versus Routers Messages
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

23. End Day 1

24. Day 2

25. 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

26. Figure 1-23: Logical Functions of the Access Router
Cable
Modem
Access Router
Router Function
DHCP
Server
Function
NAT
Function
Switch Function

27. Figure 1-24: Ethernet Switch Operation
Switching Table
Port Host
A1-44-D5-1F-AA-4C
B2-CD-13-5B-E4-65
C3-2D-55-3B-A9-4F
D C4-B6-9F
Ethernet Switch
UTP
D C4-B6-9F
UTP
UTP
UTP
Frame To C3…
Frame To C3…
C3-2D-55-3B-A9-4F
A1-44-D5-1F-AA-4C
B2-CD-13-5B-E4-65

28. Figure 1-25: Frames and Packets
A1-BD-33-6E-C7-BB
IP address =
PC in Emily’s Room
Cable
Modem
Packet in
DOCIS
Frame
Internal
Router
Packet in
Ethernet Frame
Access Router
Packet is always
carried (encapsulated)
in a frame
B2-CD-13-5B-E4-65
IP address =
PC in Study

29. Figure 1-26: Dynamic Host Configuration Protocol (DHCP)
A1-BD-33-6E-C7-BB
PC in Emily’s Room
Cable
Modem 1.
IP Address =
The ISP only
Gives each home a
Single IP address
ISP
DHCP
Server
B2-CD-13-5B-E4-65
PC in Study
Access Router
A DHCP Server
provides User PCs with
a temporary IP Address
each time the user
connects to the Internet

30. Figure 1-26: Dynamic Host Configuration Protocol (DHCP), Continued
A1-BD-33-6E-C7-BB
IP address =
PC in Emily’s Room
Cable
Modem 1.
IP Address =
Internal
DHCP
Server
ISP
DHCP
Server
2. IP Address =
Access Router
2. IP Address =
The access router’s
Internal DHCP server
Gives private IP
Addresses to each PC
B2-CD-13-5B-E4-65
IP address =
PC in Study

31. Figure 1-27: Network Address Translation (NAT)
2. Packet from
Cable
Modem
Internal
NAT
Module
Webserver
IP address=
1. Packet from
Access Router
The access router’s NAT
module translates between the
private IP addresses and
the single ISP-given IP address
PC in Study

32. Figure 1-27: Network Address Translation (NAT), Continued3.
Packet to
Cable
Modem
Internal
NAT
Module
Webserver
IP address=
4. Packet to
Access Router
PC in Study

33. Figure 1-28: The Domain Name System (DNS), Continued
DNS Table
Host Name IP Address
… …
Voyager.cba.hawaii.edu
Originating
Host’s DNS
Resolver
DNS Request Message
“The host name is Voyager.cba.hawaii.edu”
DNS Response Message
“The IP address is ”
DNS
Host

34. Figure 1-29: Converting Binary IP Addresses to Dotted Decimal Notation
8-Bit Segments
Convert Segments to Decimal
127
171 17 13
Dotted Decimal Notation

35. Elements of a Network Message (Frame) Application Application Client
Station
Switch
Server
Station
Switch
Trunk
Line
Access
Line
Switch
Trunk
Line
Outside
World
Mobile Client
Station
Switch
Router
Mobile Client
Station

36. Figure 1-22: Home Network Access Router
About 4 inches (10 cm) Wide
Switch Ports
UTP Cords
Run to Stations
Power
Jack for
External
WAN Port
UTP Cord
Runs to
Cable Modem

37. Figure 1-19: Network Interface Cards (NICs) (Photo)
PC Card NIC. Installed in PC Card slot in notebook and some PDAs.
Internal NIC. Installed inside systems unit. Plugged into expansion slot on the mother board.

38. Internal NIC
RJ-45
Jack
PCI Connector Pins

39. Computer Mother Board Mother Board PCI Slots for Expansion Boards
(NICs, etc.)
Slot for
Microprocessor
(Pentium 4)
Slots for RAM

40. Mother Board and Expansion Boards
(NIC)
Connector
Expansion
Slots
Mother Board

41. 4-Pair Unshielded Twisted Pair (UTP)
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

42. Figure 1-21: UTP Cord RJ-45 Connector and Jack
RJ-45 Jack
On a Wall
On a Switch or
On a NIC
UTP Cord
---
About as thick
as a pencil
Rugged and
Flexible
RJ-45
Connector

43. Figure 1-13: Major Network Technical Concerns
Architecture
Standards
Security
Efficiency
Wireless Communication
QoS

44. 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

45. 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

46. Figure 1-13: Major Network Technical Concerns, Continued
Security
A Major Problem
Many attacks
Growing trend toward criminal attackers

47. Figure 1-15: Firewalls Allowed Legitimate Packet Border Firewall
Attacker
Hardened
Server
Border firewall
should pass
legitimate packets
Legitimate
Packet
Hardened
Client PC
Legitimate
Host
Log File
Internal
Corporate
Network

48. Figure 1-15: Firewalls, Continued
Border
Firewall
Attack Packet
Attacker
Border firewall
should deny (drop)
and log
attack packets
Hardened
Server
Denied
Attack
Packet
Hardened
Client PC
Legitimate
Host
Log File
Internal
Corporate
Network
Network Management
Console

49. 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)

50. Figure 1-16: Virtual Private Networks (VPNs)
Site-to-Site VPN
Using Gateway
VPN
Gateway
Client
PC 1
VPN
Gateway
Remote Access
VPN Using
Gateway
Corporate
Site B
Internal
Server
Internet
Remote
Client PC 2
Host-to-Host
VPN
Corporate
Site A
Remote Client PC 3

51. 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

52. Figure 1-13: Major Network Technical Concerns, Continued
QoS
Quality of Service (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)

53. 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
2,300 Mbps is wrong
2.3 Gbps is correct
473.2 Mbps is correct

54. 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

55. 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

56. 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

57. 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

58. 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 % availability
Typical networks reach 98% today

59. 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