Chapter 10 Internet Connectivity

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Chapter 10Internet Connectivity

Chapter 10Internet Connectivity

The Complete A+ Guideto PC Repair 5/e


Describe the difference between serial and parallel data transfer

Configure a serial port and an external modem and all associated system resources and individual settings; configure an internal modem with all associated settings

Define basic handshaking between a DTE device and a DCE device

Use Windows tools to determine which system resources can be assigned to serial devices and determine if they are working properly

Chapter ObjectivesChapter Objectives


Explain basic modem concepts and analog modem limitations

Compare and contrast different modems such as analog, cable, digital, fax, satellite, and wireless modems

Perform basic modem troubleshooting

Explain the benefits of mentoring in the IT field

Chapter ObjectivesChapter Objectives


Internet Connectivity OverviewInternet Connectivity Overview

Connecting to the Internetanalog modem ISDN cable modem DSL modem satellite modem wirelessly power line cellular network.

Each of these technologies has its own installation method and configuration, but they all have in common the ability to connect a computer to an outside network.

Each of these technologies is a viable option for connectivity in a specific situation.


Modem OverviewModem Overview

One of the few serial devices left is a modem.

A modem (modulator/

demodulator) connects the

computer with the outside

world through a phone line.

A modem (modulator/

demodulator) connects the

computer with the outside

world through a phone line.

Modems can be internal or external peripheral devices.

Modems can be internal or external peripheral devices.

A modem converts a signal transmitted over the phone line to digital 1s and 0s to be read by the computer.

A modem converts a signal transmitted over the phone line to digital 1s and 0s to be read by the computer.


Modem OverviewModem Overview

• An adapter that normally has 2 ports

• Line – to phone jack

• Phone – to connect a phone

Internal ModemInternal ModemExternal ModemExternal Modem

Attaches to a serial port (9-pin male)


Serial Communication OverviewSerial Communication Overview

Serial devices such as modems transmit or receive information one bit at a time.

In contrast, parallel devices transmit data eight bits at a time.

Serial transmissions are much slower than parallel transmissions because one bit is sent at a time instead of eight.

Serial transmissions can travel longer distances more accurately than parallel transmissions.


Serial Versus Parallel TransmissionsSerial Versus Parallel Transmissions

Figure 10.3



No more than 15 feet in length

The external modem is one of the few serial devices left in use.

Parallel Cables

Internal or External?

No more than 50 feet in length

Serial Cables



Asynchronous – Transmissions that do not require a clock signal, but instead, use extra bits to track the beginning and end of data.


Tech Tip – Configuring Transmission SpeedsTech Tip – Configuring Transmission Speeds

When configuring the serial port or using an application such as HyperTerminal, the configured speed is the rate at which the serial port transmits.

This is not the speed for an external serial device that connects to the port (such as a modem).


Signals the start of dataStart bit

Stop bit

RS232C

Asynchronous Transmission TermsAsynchronous Transmission Terms

Signals the end of data

EIA standard for the serial port


Bits per second – A measurement of transmission speedbps

Baud

UART


The number of times an analog signal changes in one second.

Universal Asynchronous Receiver/Transmitter) – A motherboard chip to control the serial port or chip on an internal modem.


How to Configure Serial Ports and DevicesHow to Configure Serial Ports and Devices

Serial ports and devices such as internal modems have three important configuration parameters (and others as well, as discussed later): interrupt, I/O (input/output) address, and COM port number.

An internal modem has all these parameters; an external modem uses these same parameters, but they are assigned to the serial port to which the external modem connects.



Each serial port or device must be assigned a different I/O address.

An I/0 address is comparable to a device’s mailbox number so that the processor can differentiate between devices.

No single I/0 address may be shared by two devices.

The assigned I/0 address determines the serial port’s COM port number.



Every serial device or port must also have a different COM port number.

The operating system assigns the serial port a COM port number such as COM1, COM2, COM3, and COM4.

The system BIOS setup program can be used to configure integrated serial ports.

Common BIOS settings include, IRQ, I/0 address, COM port name, and disable.


Tech Tip – Application and Hardware Settings Must MatchTech Tip – Application and Hardware Settings Must Match

Applications that communicate or control serial devices must have the application settings match the hardware settings or communication will not occur.


A software-based method of handshaking that uses special control characters to coordinate transmissions.

XON/XOFF

RTS/CTS

DCE

More Serial Port SettingsMore Serial Port Settings

A hardware-based method of handshaking that uses signals on specific connector pins to signal the other device when to stop or send data.

Serial devices such as modems, mice and digitizers. They connect to DTE devices.

DTE Serial devices such as printers and computers.


A setting that determines how many bits make up a data word.Data bits

Parity

Stop bits


A simple method used to check for data accuracy.

The number of bits sent to indicate the end of the data word.

FIFO Used to enable or disable the UART chip’s FIFO buffer.


Determines how two serial devices communicate

Flow control

Handshaking


The order in which things happen to allow two serial devices to communicate.


Hardware HandshakingHardware Handshaking


DTE/DCE Signal ConnectionsDTE/DCE Signal Connections


Serial Device InstallationSerial Device Installation

Installing serial devices can be very frustrating. To avoid problems, install the internal modem or attach the serial device, and determine what COM port, IRQ, and I/0 settings have been assigned to the device.

Check Device Manager to ensure no conflicts have occurred.

Install and configure any software application that controls the device to match these settings.

If the application or device has any self-test feature, use it.


Serial Device TroubleshootingSerial Device Troubleshooting

Most serial device problems are IRQ, I/0 address, or COM port related.

The serial device may not be working properly due to the following reasons: (1) configuration setting conflicting with another device; (2) BIOS reassigning the COM port setting; or (3) a software’s configuration setting not matching the serial device setting.



• Symptoms for this problem include the following: – The serial device does not work.– A different device quite working.– The serial device works and then locks.– The computer locks during boot up.



• Other problems with serial devices are provided in the following list:

– Always check the simplest solution first.

– If the device is external, check to see if it needs an external power source and, if so, that the external power source is working.

– Using the wrong serial cable can cause many problems

– Check the system BIOS settings and verify the COM port used by an external serial device is not disabled in Setup, or does not conflict with an internal serial device.


Serial ConnectivitySerial Connectivity

Straight-through serial cable – used to connect an external modem to a serial port.

1

2 Null modem cable – used to connect two computers without the use of a modem.


Pros and Cons of Internal and External ModemsPros and Cons of Internal and External Modems

Internal modems require less space than external modem, however they require an expansion slot, generate more heat, and place a larger load on the computer’s power supply.

Internal modems are less expensive than external modems.

External modems connect to an existing serial port.

External modems can easily be connected to a different computer without having to take the computer apart.


Pros and Cons of Internal and External ModemsPros and Cons of Internal and External Modems

• Choosing between an internal and external modem narrows down to the following questions:

- Is there an existing expansion slot for an

internal modem?

- Is there an existing serial port available for an

external modem?

- Is money an issue?

- Is desk space an issue?


Modem Speeds and StandardsModem Speeds and Standards

• Modems transmit and receive at different speeds.

• A faster modem means less time on the phone line and less time for microprocessor interaction.

• However, because modems connect to other modems, the slowest modem determines the fastest connection speed.

• A slow modem can only operate at the speed for which it was designed.


Modem Speeds and StandardsModem Speeds and Standards

Communication modem standards are developed by CCITT. For two modems to communicate, they must adhere to the same protocol or set of rules.

Error correction – Standard for the modem to check the data for errors rather than the microprocessor.

MNP (Microcom network protocol) – A set of standards for error correction.

Data compression – A method of converting data into smaller sizes before transmission.


Communications StandardsCommunications Standards


56Kbps Modems56Kbps Modems

• The 56Kbps data transfer rate is only possible if the transmitted (analog) signal converts to digital one time during the data transmission.

• Digital phone lines are quieter than their analog counterpart, have less noise on the line, and allow faster data transmissions.


General Guidelines for Maximum Modem SpeedsGeneral Guidelines for Maximum Modem Speeds


Fax ModemsFax Modems

• A fax modem allows a modem to use the computer and printer as a fax machine.– Not all computer-based fax machines can handle

modem data transfers, however a fax modem does both modem and fax transfers.

• The Internet has changed how faxes are transmitted. – Many fax machines can send faxes to email accounts.

• VoIP (Voice over IP) – Allows voice traffic to be transmitted over the internet or data networks. Fax machines can have VoIP adapters installed.


Modem InstallationModem Installation

• Windows has an Install New Modem wizard that automates the modem installation process.

• Many technicians avoid using the wizard to detect the modem automatically. Instead, they manually select from the a list of manufacturers and models or use the disk from the modem manufacturer.

• The settings can be manually input through the Device Manager.


Analog Modem TroubleshootingAnalog Modem Troubleshooting

• In Windows, if the modem is not dialing at all, check the port setting by using the Phone and Modem Options control panel.

• Sometimes Windows disables a modem. To verify that the modem is enabled, use Device Manager.

• If the modem keeps losing connection, use the prior troubleshooting tips and try placing the modem at a lower speed.



• If the modem is an external unit, turn the modem’s power off and back on, then try the modem again.

• If the modem does not dial the number or does not output a dial tone, or if a message appears stating that the modem is not responding, check the phone cord connects to the correct jack on the modem and to the wall phone jack.

• If the modem hangs up after some time, other equipment (such as fax machine, answering machines, and portable phones) can be the cause of problem.



• If garbage (random characters) appears on the screen, check the handshaking, parity, stop bit, and baud rate settings.

• Verify that the modem works by using the Windows HyperTerminal program.

• Another HyperTerminal check is as follows: after setting the modem’s parameters, type ATDT and press .

• Type AT&F to restore the factory settings and often solve obscure problems.

Enter



• If a letter appears twice on the screen for every letter typed, check the echo mode setting in the communications software package.

• If the modem dials, but the high-pitch, screeching noise that indicates connection to another modem or fax does not sound, check the phone number.

• Use an external modem’ lights to troubleshoot the problem.


Sometimes called local echo setting; it displays typed commands.

Echo mode

Full-duplex

Half-duplex


Sending/receiving data simultaneously.

Ability to transmit and receive, but not at the same time.


Tech Tip – Modem hangs up or “No dial tone” appearsTech Tip – Modem hangs up or “No dial tone” appears

If the modem starts to dial but then hangs up, check to see if the phone cable from the wall jack to the modem inserts into the correct modem jack. This symptom also occurs if the “No dial tone” message appears.


Digital Modems and ISDNDigital Modems and ISDN

• Digital modems connect the computer directly to a digital phone line rather than to a traditional analog phone line.– One type of digital phone line available from the

phone company is an ISDN line.

• ISDN (Integrated Services Digital Network) – A digital phone line that has three separate channels, two B channels, and a D channel. – The B channel allows 64Kbps transmission speeds. – The D channel allows 16Kbps transmissions.

• ISDN is commonly used for video conferencing.


Cable ModemsCable Modems

• Cable modem can be internal or external devices.

• If the cable modem is external, two methods commonly exist for connectivity to a PC– A NIC (network interface card) is

installed in the computer and a cable attaches between the NIC and the cable modem

– The cable modem connects to a USB port.

• The USB port is the most common.



Internet data comes in through the cable TV coax cable.

The coax cable plugs into the cable modem.

The cable modem then sends the information out its built-in Ethernet port.

A network cable connects from the cable modem’s Ethernet port into an Ethernet port on the computer.

To send data to the Internet, the reverse happens.


Cable Modem TerminologyCable Modem Terminology

Upstream – Information sent to the Internet such sending an email or uploading a file

1

2

3

Downstream – Information pulled from the Internet such viewing Web pages or downloading a file

Bandwidth – The communications channel width that defines its capacity for carrying data.



• The speed of a cable modem connection depends on two things – the cable company– how many people in your neighborhood share the

same cable TV provider

• The minimum amount of hardware needed to have a cable modem depends on the cable company’s specifications.


xDSL (Digital Subscriber Line) ModemxDSL (Digital Subscriber Line) Modem

• xDSL is another modem technology that is growing in popularity. The x in the term xDSL refers to the various types of DSL that are on the market.

• The most common one is ADSL (Asymmetrical DSL), but there are many others.

• ADSL uses faster downstream speeds than upstream. This performance is fine for most home Internet users.


DSL TechnologiesDSL Technologies


DSL Modem PortsDSL Modem Ports


xDSL (Digital Subscriber Line) ModemsxDSL (Digital Subscriber Line) Modems

• A drawback to DSL is that the DSL signal needs to be separated from the normal phone traffic.

• DSL providers normally ship phone filters that must connect to each phone outlet and a phone, fax machine, or voice recorder attaches to the filter.

• The connection from the DSL modem to the phone outlet does not have a filter on it.


Troubleshooting Cable and DSL ModemsTroubleshooting Cable and DSL Modems

Since most cable and DSL modems are external, the best tool for troubleshooting connectivity problems are the lights on the front of the modem.


Troubleshooting Cable and DSL ModemsTroubleshooting Cable and DSL Modems

Once you have checked the lights and possibly checked cables, if you still feel you have a problem, power off the modem, power it back on, and reboot your computer. Give the modem a couple of minutes to initialize.


Cable/DSL Modem ConnectivityCable/DSL Modem Connectivity


Satellite ModemSatellite Modem

• An option available to areas that do not have cable or DLS service is satellite connectivity. – The satellite relays communication back to receivers on

Earth.– Satellite connectivity requires a satellite dish and satellite

modem as a minimum.

• Satellite Modem – A type if modem that can provide Internet access at speeds faster than an analog modem, but slower than cable or DSL access. – With a satellite modem, TV programs accessed via satellite

can be watched at the same time Web pages are downloaded from the Internet.


Satellite ModemsSatellite Modems

Initial costs can be high

If other people use the same service, speed is decreased during peak periods.

4

1

2

3 If other people use the same service, speed is decreased during peak periods.

Initial connections have a time lag; multiplayer games are not practical.

Weather affects performance.5

VPNs are not normally supported.6


Laptop ModemsLaptop Modems

• Portable computers sometimes have a modem PC card or ExpressCard installed in them. – Older modem PC Cards are Type II cards that fit into

a Type II or a Type III slot.

• Some older modem cards are combo cards – they are both a modem and a NIC.

• Modem PC Cards have a special connector called a dongle that attaches to them and allows an RJ-11 cable to be plugged into the card.


Laptop ModemsLaptop Modems

• Dongles can also be used with laptop network PC Cards.

• Some vendors’ dongles are proprietary. • An increasingly popular feature with laptops is

connectivity called wireless broadband.• Wireless Broadband – A feature available from

service providers that allows PC Cards, USB modems, mobile data cards, or integrated laptop connectivity to have the ability to receive, create, and communicate Internet information within a specific coverage area.


3Com NIC/modem combo PC Card with a dongle3Com NIC/modem combo PC Card with a dongle

Figure 10.12


Modem Preventive MaintenanceModem Preventive Maintenance

• The old adage “an ounce of prevention is worth a pound of cure” is never truer than in the case of modems.

• A power surge can come across a phone line just as it can through an electrical outlet.

• To provide protection for the modem and the computer, purchase a special protection device called a phone line isolator or a modem isolator at any computer or phone store.


Soft Skills - MentoringSoft Skills - Mentoring

• Every great technician can tell you that they had at least one mentor along the way.

• No technician can attain his or her ultimate level without being mentored and mentoring someone else along their career path.

• Mentoring is an important part of life. Not only should you consider being mentored, but also, along your career path, you should consider mentoring others.


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