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Transcript of CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes...
![Page 1: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/1.jpg)
CHAPTER CHAPTER
ModemsModems
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Chapter Objectives• Discuss basic modem related issues
– Standards, Hayes compatibility etc.
• Describe the different types of practical modems available– Internal, external, null, short-haul modems etc.
• Present the profile of sample practical modems– Asynchronous and synchronous modems
• Show the establishment of a fiber-optic communication link using the fiber-optic interface
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Chapter Modules• Modem Functional Considerations• Internal, External and Portable Modems• A Modem Profile• Modem Software Installation• A Practical Asynchronous/Synchronous Modem• Faster Modem Standards• Fiber-optics Connection• Null Modem and Short-haul Modem• Cable Modem• DSL Modem
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END OF CHAPTER END OF CHAPTER INTRODUCTIONINTRODUCTION
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MODULE
Modem Functional Considerations
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Module Objectives
• List the two types of modem standards• Describe the features that are
standardized in modem communication– Modulation, data compression etc.
• Explain the relevance of standards to speed
• Discuss Hayes compatibility• List a few common modem features
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Major Modem Standards
• ITU standard– Universal standard– Currently in use
• Bell standard– Earlier low speed modem standard– No more in use
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Standards in Modem Communication
• Modulation standard• Data compression standard• Error correction Standard
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Speed and Modulation Standards
• Each speed is associated with a modulation standard
• V.34 is an example standard for the communication speed of 28,800 bps
• Higher speed modems can operate at lower speeds as well– E.G 28,800 bps modem can
communicate at 14,400 bps
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Data Compression Standards in Modem
• MNP 5• ITU V.42 bis
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Error Correction Standard
• MNP 2-4
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Understanding Hayes Compatibility
• IBM is to micros what Hayes is to modems
• Hayes compatibility– Ensured by adherence to the Hayes
command set known as the AT command set
– Ensures wide availability of software
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Command Translation for PCs and Modems
• Commands for the PC– Translated into machine language and
executed• E.G. Identifying a file for transmission
• Commands for the modem– Generated in Hayes AT command set
form and transmitted to the modem for execution• E.G. Command instructing the modem to dial
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Command Translation
Software Intel Micro Modem
Intel Machine Code
Hayes AT Command
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Modem Features
• Auto-dial• Auto-answer• Reverse calling• All the above features are standard
in today’s Modems
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END OF MODULEEND OF MODULE
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MODULE
Internal, External and Portable Modems
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Overview of Internal and External Modems
• Internal modem– Installed in the expansion slot– Usually cheaper– Occupies one expansion slot
• External modem– Connects to the serial port of the computer– More expensive – Does not occupy an expansion slot – But, it does utilize one of the available
communication ports
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Internal Modems
Source: Black Box
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External Modems
Source: Black Box
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External Modem Ports and Connection
To Com2Port
To PhoneJack RJ 11
Connection
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Modems for the Notebooks or PC Card
Modem• Credit card size• Connects to the PCMCIA slot
– Currently, known as PC card slots
• PC cards have undergone major refinements– Efficient in their operation– Support high-speed communication
devices
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PC Card Modems
Source: Black Box
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Multi-Purpose PC Cards
Source: Black Box
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END OF MODULEEND OF MODULE
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MODULE
A Modem Profile
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Module Objectives
• Examine the profile of an actual commercial modem
• Discuss the standards as they relate to speed, data compression and error correction
• Describe the FAX related communication details of the modem
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Profile of a Modem : Black Box Modem 288 Standards
• Standards– ITU V.92, ITU V.90, ITU V.34, v.32bis, v.23,
v.22bis, v.22, v.21, Bell 101 and Bell 212a
• Protocols– Asynchronous and synchronous
• Speed– V.90 ------ 56Kbps– V.34 -------> 28.8 Kbps– Others up to 14.4 Kbps– Possible up to 115.2 Kbps
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Profile: Operation, Interface and Connectors
• Operation– 2 wire dial-up
• Interface– RS-232C
• Connectors– 1 DB25 female– 2 RJ11 female
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Profile: Speed and Compression Standards
• V.90– Supports 56 Kbps
• V.34– Supports 28.8 Kbps
• V.32– Supports 14.4 Kbps
• V.42bis– Data compression standards– Up to 4 to 1 compression is possible
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Profile: Error Correction and Other Data
Compression Standards• MNP 2-4 and 10
– Error correction
• MNP 5 – Data compression
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Combined Effect of Speed and Compression
Standards
• Combined effect of v.34 and v.42bis data compression– 115.2 Kbps– This is only a theoretical reality– Practical speeds can be considerably
slow
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Effect of Compression on File Transfer
• Highest transfer speeds cannot be achieved in the case of already compressed files– Example: jpg, mp3 etc.– Because the above files are already
compressed
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Profile: Fax Communication
• Fax details– 14.4 Kbps speed– Class 1 and 2 fax software support– Works with class 3 fax machines
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END OF MODULEEND OF MODULE
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MODULE
Modem Software Installation
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Module Objectives
• Demonstrate the step-by-step installation of a modem in the Windows 95 operating system
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Installation Overview
• The task is to install a Hayes Accura 28.8 modem on Com2 port
• Overview of the Steps– Open the control panel– Choose the Modem icon– Proceed with the installation as
instructed and finally specify the properties of the installed modem
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Demonstration of Modem Software Installation
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Accessing Modem Installation Icon Through
Control Panel
Start Settings
Control Panel Modems
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Modem Icon in Control Panel
Double Click
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Select the Modem
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Selecting the Modem
Load the driver from the diskIf the modem is not found in the List.
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Non-Mainstream Modem
• If the modem is not of a popular type, then the driver must be loaded from a location on the disk
• In the above case, select the option that says “Have Disk”
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Selecting the Port
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Finishing the Installation
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Installed
Modem
1
2
3
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Modem General Properti
esIncrease
the speed to the
maximum.
1
2
3
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Connection
Properties
1
2
3 4
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Port Settings
1
2
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Advanced Connection Settings
1 2
3
4
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Dialing Propertie
s1
2
3
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END OF MODULEEND OF MODULE
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MODULE
A Practical Asynchronous/Synchronous
Modem
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Module Objectives
• Examine briefly the profile of an asynchronous/synchronous modem
• Discuss speed related factors• Give an illustration of the typical
use of a synchronous modem
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Profile of an Asynchronous/Synchronou
s Modem• Blackbox 32fast modem• Claimed speed
– 72k bps synchronous• Uses sync. Data compression to send data
under HDLC/SDLC
– 115.2k bps asynchronous
• Best compression is automatically chosen– Between v.42 bis and MNP 5
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Profile of Asynchronous/Synchronou
s Modem• Other features
– Trellis-coded modulation– MNP 4 error correction
• Suggested lines– 2 or 4 wired leased lines– Switched phone lines may not provide
optimum performance
• UART connection – For effective high-speed transmission
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Typical Use of a Synchronous Modem
Mainframe
Front EndProcessor
ClusterController
Terminal
SynchronousModem
Leased Line
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END OF MODULEEND OF MODULE
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MODULE
Faster Modem Standards
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Faster Modem Standards• The current fastest analog modem operates
at a speed of 56 Kbps• Standards
– ITU V.90– X2– K56flex
• X2 was introduced by US Robotics that has been acquired by 3 Com
• K56flex standard was introduced by Rockwell and Lucent Technologies
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Practical Speed Considerations
• 56 Kbps has not been achieved in many tests in practice
• Speed is usually in the region of 45k bps or less
• FCC restriction on download speed– Currently the speed limitation is 53
Kbps
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56 Kbps /V.90 Information
• Cedric Walravens’ web site is a good source of information on 56K /V.90 modems and communication
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Data Compression Limitations
• High speed modems use compression to increase the throughput
• Files such as image files are already compressed– There is little leeway for further
compression – Results in a drop in the communication
speed
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Quality of the Phone Lines
• Certain phone lines cannot support 56K bps speed
• Central office that services a particular area may not have the latest switching equipment
• Testing the line for 56K bps support– X2.usr.com/linetest1.html
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Bonding of Telephone Lines to Achieve Higher Speeds
(112 Kbps)
ComputerModem with
BondingCapability
Phone Lines
Bonding of two phone lines can provide atotal bandwidth of 112K bps.
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END OF MODULEEND OF MODULE
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MODULE
Fiber-Optics Connection
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Module Objectives
• Examine a fiber-optic connection used for extending the length of the communication link
• Give an illustration of a practical fiber-optic link
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Fiber-optic Connection for RS-232C
• Extends RS-232C connection to nearly 2 . 5 miles
• Fiber interface (line driver) specifications– Transfer mode
• Synchronous and asynchronous
– Speed• 56 K bps for sync.• 64 K bps for aysnc.• Selectable depending on the connection
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Fiber Optic Line Driver
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Some Fiber-optic Connections :Fiber Modems
Host
Fiber Line Drivers Terminal
2.5 miles
RS 232
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Fiber-optic Line Drivers
T1
Building 1 Building 2
Fiber-optic Line Driver
Router,Bridge.(Support Videoconferencing)
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Practical Fiber Optics Connection
![Page 75: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/75.jpg)
END OF MODULEEND OF MODULE
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MODULE
Null Modems and Short-Haul Modems
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Null Modem
• Use for connecting two computers together – Communicate through their
respective serial ports
• Digital signals are not modulated
Null Modem
Send Send
Receive Receive
Comp 1 Comp 2
![Page 78: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/78.jpg)
Characteristics of the Null Modem
• Cross-over connection– Enables the sending and receiving of signals
to facilitate communication
• Instead of a null-modem, one may also use a crossover cable
• In the past, null modems were used with software like lap-link– The primary purpose was for file transfer
• Null modem is being replaced by a simple null modem cable
![Page 79: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/79.jpg)
Null Modem Cable Connection
Null Modem
Comp 1 Comp 2Cable 1 Cable 2
Comp 1 Null Modem Cable Comp 2
Past
Present
![Page 80: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/80.jpg)
Other Ways to Connect Two Computers (Network)
Comp 1
RJ 45Cross-over Cable
Comp 2
NIC
![Page 81: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/81.jpg)
Other Ways to Connect Two Computers (Network)
Comp 1 Comp 2
Infrared Connection
Infrared Port Device
![Page 82: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/82.jpg)
Crossover Cable Use
• Laplink– A software that is used for transferring
information between computers
• The Laplink cable that is used to connect computers together is indeed a crossover cable– In this case, the computers are connected
either over the serial, parallel or USB ports
• Nowadays, a popular method of exchanging information between computers is to use Infrared
![Page 83: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/83.jpg)
Short-Haul Modem
• Purpose– Extend the length of a RS-232 serial
connection
• Signals are not modulated– The term modem is a misnomer
• Signals are boosted so that they may be carried over a longer distance
![Page 84: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/84.jpg)
Short-Haul Modem
Asynchronous.Host
Short-Haul ModemRack
UNIX Computer
SHM Term.
SHMSHM Term.
SHM Term.
SHM Term.
![Page 85: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/85.jpg)
Practical Implementation
Source: Black Box
![Page 86: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/86.jpg)
In Summary
• Traditional modems– Perform modulation
• Nontraditional modems– Do not perform any modulation
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END OF MODULEEND OF MODULE
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MODULE
Cable Modems
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Cable Modem
• A modem that is used for connecting a computer to the cable TV line
• The purpose is to facilitate high speed access to the Internet
• Cable modem is a broadband technology device– The cable carries multiple channels
including TV channels and upstream and downstream data channels
![Page 90: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/90.jpg)
Typical Cable Modem Connection (Single IP
Address)
Cable Modem
Computer
Coaxial Cable
UTP (Cat 3 – 5)
NIC
![Page 91: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/91.jpg)
Sharing Single IP Address with Multiple Computers
(10base2)
1
1
•A proxy server can be used.•Windows 2000.•Windows 98 Second edition supports the sharing of •one PC for multiple PC access to the Internet.
Source: Tim Higgins Site
2
![Page 92: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/92.jpg)
Sharing Single IP Address with Multiple Computers
(10baseT)
1
1
•A proxy server can be used.•Windows 2000.•Windows 98 Second edition supports the sharing of •one PC for multiple PC access to the Internet.
Source: Tim Higgins Site
2
![Page 93: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/93.jpg)
Two Computers Sharing One IP without a Hub
2
•A proxy server can be used.•Windows 2000.•Windows 98 Second edition supports the sharing of •one PC for multiple PC access to the Internet.
Source: Tim Higgins Site2
1
2
3
![Page 94: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/94.jpg)
Computer
Cable Modem LAN Connection (Multiple IP
Addresses)
Cable Modem Hub
Coaxial Cable
NICComputer
NICComputer
NIC
UTP (Cat 3 – 5)Crossover Cable?
UTP (Cat 3 – 5)
![Page 95: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/95.jpg)
Cable Modem Customer Connections
Customer Customer Customer
Cable Service
Provider
CM CM CM
CMTS
CM: Cable ModemCMTS: Cable Modem Termination System
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Cable Modem Limitation
• Each cable drop is shared by a number of customers
• As the number of customers increases in a trunk the bandwidth available per customer decreases
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Cable Modem Types
• Internal Modems– Installed into a PC’s expansion slot
• External Modems– An external box connected to the
computer’s NIC• External Web TV Box
– Used with Web TV setups – A return channel may be provided
through a POTS line
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Cable Modem Standards
• The current versions are known as the second generation modems
• US Standards– MCNS/DOCSIS 1.0/1.1– A de facto standard– IEEE is yet to propose or approve a
standard• European
– DVB/DAVIC 1.3/1.4/1.5
![Page 99: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/99.jpg)
The Tutorial for Cable Modems
• www.cable-modems.org– Contains useful information on cable modems
• Access to the tutorial– http://www.cable-modems.org/tutorial/
• Access to Q and A– http://www.cable-modems.org/Q&A/
• Appreciation and credit– Some of the slides used in this chapter are from
the above web site as acknowledged in the appropriate slides
– Also, visit the site for a description of some of the technical terms associated with cable modems
![Page 100: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/100.jpg)
Additional Sites
• www.cablemodemdatacom.com– Extensive information with good
graphics
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Modulation and Demodulation Frequencies
Source: http://www.cable-modems.org/tutorial/01.htm
![Page 102: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/102.jpg)
Speed and Bandwidth• Shannon’s Law
– Speed is proportional to bandwidth
• In most cases, downstream speed is higher than upstream speed
• Higher upstream speed is desired in certain cases– Hosting of a web server
• Symmetric streams are desired for video conferencing
![Page 103: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/103.jpg)
Maximum Bandwidth
• Upstream– Lower frequencies are used– Up to 3Mbps
• Downstream– Higher frequencies are used– Between 27-56 Mbps
• Note that communication speed is proportional to available bandwidth
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Downstream Communication Characteristics
Source: http://www.cable-modems.org/tutorial/08.htm
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Upstream Communication Characteristics
Source: http://www.cable-modems.org/tutorial/09.htm
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OSI-ISO Reference Model and Cable Modem
Communication
Source: http://www.cable-modems.org/tutorial/02.htm
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Sample Cable Modem Companies
• 3Com• CISCO Systems• Toshiba• Sony• More DOCSIS compatible Cable
Modems– A gallery of selected cable modems
from cable-modems.org
![Page 108: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/108.jpg)
Sample Cable
Modem
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Sample Product Demonstration
• 3Com Cable Modem CMX product demonstration– Explore the purpose of the different
status lights on the modem– Try this to see the product feature
and rotate the modem to view the different sides of the modem
![Page 110: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/110.jpg)
Possible Downside
• Potential downsides to the cable modem are discussed in this ZDnet article
![Page 111: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/111.jpg)
Advantages and Disadvantages
• Advantages– Higher speeds compared to analog
connections– The connection is always on– Possible assignment of static IP addresses
• Disadvantages– Speed drops with an increase in the number
of customers on a cable drop– Higher costs compared to analog
connections
![Page 112: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/112.jpg)
FAQs
• A collection of 100 FAQs from cable-modems.org– Includes FAQs for DSL as well
![Page 113: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/113.jpg)
Other Cable Modem Links
• ZDnet home page on cable modem• Cable modem help web site• Cable modem net information site• Tom Higgins’ cable modem site
– Recommended• Cable modem books
– A listing of selected books from cable-modems.org
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END OF MODULEEND OF MODULE
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MODULE
DSL Modems
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DSL Modem
• A modem that is used for connecting a computer to the Digital Subscriber Line (DSL)
• The purpose is to facilitate high speed access to the Internet
• DSL modem is a broadband technology device– The regular telephone line carries the DSL line
as well– Therefore, there are multiple channels present
on the POTS line delivering the DSL connection
![Page 117: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/117.jpg)
Simple DSL Line Drop
Source: xDSL Technology Web Site
![Page 118: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/118.jpg)
Another xDSL Line Drop
Soource: XDSL
![Page 119: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/119.jpg)
Typical DSL Modem Connection
(Single IP Address)
DSL Modem
Computer
POTS line
UTP (Cat 3 – 5)
NIC
10/100 Mbps(*Cat 5 is recommended)
![Page 120: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/120.jpg)
Sharing Single IP Address with Multiple Computers
(10base2)
![Page 121: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/121.jpg)
Sharing Single IP with Multiple Computers
(10baseT)
Source: xDSL
![Page 122: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/122.jpg)
Sharing Single IP with Two Computers without a Hub
![Page 123: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/123.jpg)
DSL Modem LAN Connection
(Multiple IP Addresses)
Source: xDSL
![Page 124: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/124.jpg)
Source: DSL Reports
![Page 125: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/125.jpg)
DSL Resources
• DSL Reports itself is a good DSL web site
• A good reference to DSL Resources from DSL reports
• A good page that shows graphically the speed comparison of DSL with other technologies
![Page 126: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/126.jpg)
Typical ADSL Connection
Source: ADSL Tutorial from adsl.com
![Page 127: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/127.jpg)
Cable Modem Limitation
• Each cable drop is shared by a number of customers
• As the number of customers increase in a trunk the bandwidth available per customer decreases
![Page 128: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/128.jpg)
ASDL Modem Types
• Internal Modems– Installed into a PC’s modem
• External Modems– An external box connected to the
computer’s NIC
![Page 129: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/129.jpg)
Cable Modem Standards
• The current versions are known as the second generation modems
• US Standards– MCNS/DOCSIS 1.0/1.1– A de facto standard– IEEE is yet to propose or approve a
standard• European
– DVB/DAVIC 1.3/1.4/1.5
![Page 130: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/130.jpg)
The Tutorial for Cable Modems
• www.cable-modems.org– Contains useful information on cable modems
• Access to the tutorial– http://www.cable-modems.org/tutorial/
• Access to Q and A– http://www.cable-modems.org/Q&A/
• Appreciation and credit– Some of the slides used in this chapter are from
the above web site as acknowledged in the appropriate slides
– Also, visit the site for a description of some of the technical terms associated with cable modems
![Page 131: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/131.jpg)
Modulation and Demodulation Frequencies
Source: http://www.cable-modems.org/tutorial/01.htm
![Page 132: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/132.jpg)
Maximum Bandwidth
• Upstream– Lower frequencies are used– Up to 3Mbps
• Downstream– Higher frequencies are used– Between 27-56 Mbps
• Note that communication speed is proportional to available bandwidth
![Page 133: CHAPTER Modems. Chapter Objectives Discuss basic modem related issues –Standards, Hayes compatibility etc. Describe the different types of practical modems.](https://reader030.fdocuments.in/reader030/viewer/2022032705/56649db35503460f94aa30c4/html5/thumbnails/133.jpg)
Downstream Communication Characteristics
Source: http://www.cable-modems.org/tutorial/08.htm
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Upstream Communication Characteristics
Source: http://www.cable-modems.org/tutorial/09.htm
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OSI-ISO Reference Model and Cable Modem
Communication
Source: http://www.cable-modems.org/tutorial/02.htm
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Sample DSL Modem Companies
• 3Com• CISCO Systems• Alcatel
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Sample Cable
Modem Source: 3Com Modem
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Sample Product Specifications
Source: 3Com
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Sample Product Demonstration
• 3Com ADSL Modem Demonstration– http://www.3com.com/client/pcd/
homeconnect/dsl/images/prod_sidenav.gif
– Explore the purpose of the different status lights on the modem
– Try this to see the product feature and rotate the modem to view the different sides of the modem
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Possible Downside
• Potential downsides to ADSL
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Advantages and Disadvantages
• Advantages– Higher speeds compared to analog
connections– The connection is always on– Possible assignment of static IP addresses– Existing POTS line can be used
• Disadvantages– Higher costs compared to analog
connections– May not be available at all locations
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Other DSL Links
• DSL Reports web site contains a good collection of selected links
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END OF MODULE END OF MODULE
END OF CHAPTER END OF CHAPTER