22 the internet

The InternetThe Internet

Client/Server Client/Server Applications on the Applications on the InternetInternet

The TCP/IP Suite of The TCP/IP Suite of ProtocolsProtocols How a client addresses a server How a client addresses a server

application on another computerapplication on another computer

How protocols in TCP/IP suite are How protocols in TCP/IP suite are used on intranets and Internet to used on intranets and Internet to support client/server applicationssupport client/server applications

Using IP and Port Using IP and Port Addresses to Identify Addresses to Identify ServicesServices

Common Port Common Port AssignmentsAssignments

TCP/IP Network LayersTCP/IP Network Layers

TCP/IP Protocol LayersTCP/IP Protocol Layers

Applications protocolsApplications protocols

– Applications make an API call to the OSApplications make an API call to the OS

TCP/IP protocols used by the OS for TCP/IP protocols used by the OS for network communicationnetwork communication

Network protocols used by hardwareNetwork protocols used by hardware

– Included in firmware and drivers on a single Included in firmware and drivers on a single NICNIC

– Protocol used depends on type of physical Protocol used depends on type of physical network data is traveling on (eg, PPP)network data is traveling on (eg, PPP)

TCP/IP Protocols Used TCP/IP Protocols Used by the OS for Network by the OS for Network CommunicationCommunicationTCPTCP Guarantees packet deliveryGuarantees packet delivery

Connection-oriented protocolConnection-oriented protocol

UDPUDP Does not guarantee deliveryDoes not guarantee delivery Connectionless protocolConnectionless protocol

IPIP Breaks up and reassembles data into Breaks up and reassembles data into packets; routes them to their packets; routes them to their destinationdestination

ARPARP Locates host on a local networkLocates host on a local network

RARRARPP

Discovers Internet address of host on Discovers Internet address of host on local networklocal network

ICMPICMP Communicates problems with Communicates problems with transmissiontransmission

Internet Protocol (IP)Internet Protocol (IP)

Transmission Control Transmission Control Protocol (TCP)Protocol (TCP)

TCP/IP UtilitiesTCP/IP Utilities

TCP/IP Utilities TCP/IP Utilities ((continuedcontinued))

Other ToolsOther Tools

Microsoft SNMP AgentMicrosoft SNMP Agent

– Provides system management for networksProvides system management for networks

– Can be security riskCan be security risk

NSLookupNSLookup

– Reports information about Internet name Reports information about Internet name spacespace

– Requests information about domain name Requests information about domain name resolutions from DNS server’s zone dataresolutions from DNS server’s zone data

Ways to Connect to Ways to Connect to the Internetthe Internet Standard dial-up modemStandard dial-up modem

DSLDSL

Cable modemCable modem

Dial-up NetworkingDial-up Networking

Uses PPP (Point To Point Protocol) to Uses PPP (Point To Point Protocol) to send packets of data over phone send packets of data over phone lineslines

Must install modem and drivers to Must install modem and drivers to run itrun it

Must install TCP/IP and bind it to the Must install TCP/IP and bind it to the modemmodem

More info: http://en.wikipedia.org/wiki/Point-to-Point_Protocol http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/ppp.htm

PPP – Point to Point PPP – Point to Point ProtocolProtocol

6 Fields Make Up the PPP FrameThe following descriptions summarize the PPP frame fields illustrated above:

Flag—A single byte that indicates the beginning or end of a frame. The flag field consists of the binary sequence 01111110.

Address—A single byte that contains the binary sequence 11111111, the standard broadcast address. PPP does not assign individual station addresses. Control—A single byte that contains the binary sequence 00000011, which calls for transmission of user data in an unsequenced frame. A connectionless link service similar to that of Logical Link Control (LLC) Type 1 is provided.

PPP – Point to Point PPP – Point to Point Protocol – (Continued)Protocol – (Continued)

6 Fields Make Up the PPP Frame

The following descriptions summarize the PPP frame fields illustrated above:

Protocol—Two bytes that identify the protocol encapsulated in the information field of the frame. The most up-to-date values of the protocol field are specified in the most recent Assigned Numbers Request For Comments (RFC).

Data—Zero or more bytes that contain the datagram for the protocol specified in the protocol field. The end of the information field is found by locating the closing flag sequence and allowing 2 bytes for the FCS field.

PPP – Point to Point PPP – Point to Point Protocol – (Continued)Protocol – (Continued)

6 Fields Make Up the PPP FrameThe following descriptions summarize the PPP frame fields illustrated above:

The default maximum length of the information field is 1,500 bytes. By prior agreement, consenting PPP implementations can use other values for the maximum information field length.

Frame check sequence (FCS)—Normally 16 bits (2 bytes). By prior agreement, consenting PPP implementations can use a 32-bit (4-byte) FCS for improved error detection.

ModemsModems

Devices used by PCs to communicate Devices used by PCs to communicate over phone linesover phone lines

Can be an external device connected Can be an external device connected to a USB or serial portto a USB or serial port

Can be a modem card using either an Can be a modem card using either an ISA or PCI slotISA or PCI slot

Can be a smaller and less expensive Can be a smaller and less expensive modem riser cardmodem riser card

External ModemExternal Modem

Modem CardModem Card

All About ModemsAll About Modems

Are both hardware and firmwareAre both hardware and firmware

MOdulation/DEModulationMOdulation/DEModulation

– Convert digital data to analog, then back to Convert digital data to analog, then back to digitaldigital

Provide an RJ-11 connectionProvide an RJ-11 connection

Can be half-duplex or full-duplexCan be half-duplex or full-duplex

Modulation/Modulation/DemodulationDemodulation

RJ-11 ConnectionRJ-11 Connection

How Modems Are How Modems Are RatedRated By how they set communication By how they set communication

rules (handshaking)rules (handshaking)

By how fast they pass data over By how fast they pass data over phone lines (measured in bits per phone lines (measured in bits per second or bps)second or bps)

HandshakingHandshaking

In telecommunication and microprocessor systems, the term handshaking has the following meanings:

1. In data communications, a sequence of events governed by hardware or software, requiring mutual agreement of the state of the operational modes prior to information exchange

2. The process used to establish communications parameters between two stations

Handshaking follows the establishment of a circuit between the stationsestablishment of a circuit between the stations and precedes information transfer.precedes information transfer. It is used to agree upon such parameters as information transfer rate, alphabet, parity, interrupt procedure, and other information transfer rate, alphabet, parity, interrupt procedure, and other protocol featuresprotocol features

Modem SpeedModem Speed

56 Kbps56 Kbps

– Most commonly used modem speed rating Most commonly used modem speed rating todaytoday

V.92 standardV.92 standard

– Current standard for 56 Kbps transmissionCurrent standard for 56 Kbps transmission

Maximum speed is often written into the Maximum speed is often written into the manufacturer’s name for the modemmanufacturer’s name for the modem

The Ceiling on Modem The Ceiling on Modem SpeedsSpeeds Analog phone lines were designed Analog phone lines were designed

for transmission of human voice; for transmission of human voice;

– Affects ability to attain high Affects ability to attain high transmission speeds for datatransmission speeds for data

Noise (line disturbance)Noise (line disturbance)

Modem StandardsModem Standards

Written by the CCITT, now called Written by the CCITT, now called the ITU (International the ITU (International Telecommunication Union)Telecommunication Union)

The more standards a modem The more standards a modem supports, the better it can supports, the better it can communicate with a variety of communicate with a variety of other modemsother modems

Modem Transmission Modem Transmission StandardsStandards

Modem Transmission Modem Transmission Standards (Standards (continuedcontinued))

Modem Transmission Modem Transmission Standards (Standards (continuedcontinued))

Data CompressionData Compression

Performed by firmware housed on the Performed by firmware housed on the modemmodem

Follows one of three protocols (which Follows one of three protocols (which also perform error correction)also perform error correction)

– MNP-5MNP-5

– CCITT V.42CCITT V.42

– V.42bisV.42bis

Error CorrectionError Correction

Performed by firmware housed on the modemPerformed by firmware housed on the modem Breaks data up into small packets (frames)Breaks data up into small packets (frames)

– Sending modem performs calculations on a Sending modem performs calculations on a frame, then sums calculations into a frame, then sums calculations into a checksum, which is attached to the data checksum, which is attached to the data frameframe

– Receiving modem performs same Receiving modem performs same calculations and runs a comparison of values calculations and runs a comparison of values before acceptingbefore accepting

Slows the process but guarantees almost 100% Slows the process but guarantees almost 100% accuracyaccuracy

Key Points about Key Points about HandshakingHandshaking Answering modem sends a guard tone Answering modem sends a guard tone

so connection is not brokenso connection is not broken

Answering modem establishes a carrierAnswering modem establishes a carrier

Equalization stage; modem speed (line Equalization stage; modem speed (line speed) is set between modemsspeed) is set between modems

Modem speakers turn off; methods of Modem speakers turn off; methods of data transmission are agreed ondata transmission are agreed on

Serial Port (UART) Serial Port (UART) SettingsSettings UART chip is responsible for communications UART chip is responsible for communications

over a serial portover a serial port

– External modem is likely to use a serial portExternal modem is likely to use a serial port

– Internal modem has serial port (UART) logic Internal modem has serial port (UART) logic on the modem card and must be assigned its on the modem card and must be assigned its own COM port that its UART controlsown COM port that its UART controls

Port settings control serial-port communicationPort settings control serial-port communication

Info on UARTInfo on UART

Pronounced Pronounced u-art,u-art, and short for and short for uuniversal niversal aasynchronous synchronous rreceiver-eceiver-ttransmitter,ransmitter, the UART is a computer component the UART is a computer component that handles asynchronous serial communication. Every that handles asynchronous serial communication. Every computer contains a UART to manage the serial ports, computer contains a UART to manage the serial ports, and some internal modems have their own UART and some internal modems have their own UART

As modems have become increasingly fast, the UART As modems have become increasingly fast, the UART has come under greater scrutiny as the cause of has come under greater scrutiny as the cause of transmission bottlenecks. If you are purchasing a fast transmission bottlenecks. If you are purchasing a fast external modem, make sure that the computer's UART external modem, make sure that the computer's UART can handle the modem's maximum transmission rate can handle the modem's maximum transmission rate

The newer 16550 UART contains a 16-byte buffer, The newer 16550 UART contains a 16-byte buffer, enabling it to support higher transmission rates than the enabling it to support higher transmission rates than the older 8250 UART older 8250 UART

Port SettingsPort Settings

Port Settings (Port Settings (continuedcontinued))

Port and Modem Port and Modem SettingsSettings Communication between DTE and Communication between DTE and

DCE (computer and modem) is DCE (computer and modem) is controlled by port settingscontrolled by port settings

– RS-232RS-232

– DigitalDigital

– Port speedPort speed

Port and Modem Port and Modem Settings (Settings (continuedcontinued))

Communication between two DCE devices (two Communication between two DCE devices (two modems) is controlled by modem settingsmodems) is controlled by modem settings

– Phone linePhone line

– AnalogAnalog

– Line speedLine speed

Use Rule of Thumb – If the device plugs into the computer serial port and works normally, the device is wired as DCE (or the connection cable is a crossover type that makes it work as a DCE). If the device connects to the computer port using a "null modem" crossover cable, it is wired as DTE.

Port and Modem Port and Modem Settings (Settings (continuedcontinued))

DTE or DCE DeviceDTE or DCE Device

How Can I Identify DTE or DCE Type Connections?

What devices have DTE type RS-232 ports? A DTE device is "Data Terminal Equipment", this includes Computers, Serial Printers, PLC's, Video Cameras, Video Recorders, Video Editors, and most devices which are not used to extend communications. Think COMPUTER for DTE.

What devices have DCE type RS-232 ports? A DCE device is "Data Communications Equipment", this includes devices intended to plug directly into a DTE port, PDA cables, Modems and devices that extend communications like a modem, such as RS-422, RS-485, or Fiber Optic converters or Radio Modems. Think MODEM for DCE.

Modem FeaturesModem Features

Caller IDCaller ID

Call waitingCall waiting

Display readoutDisplay readout

Fax capabilitiesFax capabilities

Flash ROMFlash ROM

Plug and Play for Plug and Play for WindowsWindows

Voice/data Voice/data capabilitycapability

Auto-answerAuto-answer

Expansion slot or Expansion slot or port typeport type

Installing an Internal Installing an Internal ModemModem Read documentationRead documentation

Determine available serial portDetermine available serial port

Set jumpers or DIP switches on modem cardSet jumpers or DIP switches on modem card

Turn off computer; remove case; mount Turn off computer; remove case; mount cardcard

Replace coverReplace cover

Plug phone line from house into line jack on Plug phone line from house into line jack on modemmodem

Setting Jumpers on an Setting Jumpers on an Internal ModemInternal Modem

Installing an External Installing an External ModemModem Connect high-quality cable to Connect high-quality cable to

modem and to serial or USB portmodem and to serial or USB port

Plug electrical cord from modem Plug electrical cord from modem into an 110V AC outletinto an 110V AC outlet

Plug phone line from house into Plug phone line from house into line jack on modemline jack on modem

Configuring a Modem Configuring a Modem Using Windows XPUsing Windows XP Windows Plug and Play will detect new Windows Plug and Play will detect new

hardware devicehardware device Verify the OS configured the modem Verify the OS configured the modem

correctlycorrectly Verify that modem speed is set to highest Verify that modem speed is set to highest

value in Maximum Port Speed text boxvalue in Maximum Port Speed text box To use Windows to make calls without To use Windows to make calls without

using other software, create a dial-up using other software, create a dial-up Networking ConnectionNetworking Connection

Creating a Windows XP Creating a Windows XP Dial-up Network Dial-up Network ConnectionConnection

Ways to Test a ModemWays to Test a Modem

Use the HyperTerminal utilityUse the HyperTerminal utility

Use the OS to perform a Use the OS to perform a diagnostic testdiagnostic test

– AT commandsAT commands

Testing a Modem with Testing a Modem with AT CommandsAT Commands

Troubleshooting Troubleshooting Guidelines for ModemsGuidelines for Modems What works and what doesn’t work?What works and what doesn’t work?

What worked in the past but does not What worked in the past but does not work now?work now?

What has changed since things last What has changed since things last worked?worked?

Ask questions of usersAsk questions of users

Try simple things firstTry simple things first

Potential Modem Potential Modem ProblemsProblems Modem does not respondModem does not respond

Modem says there is no dial tone, but Modem says there is no dial tone, but you can hear ityou can hear it

Modem dials, then says the other end Modem dials, then says the other end is busy, even when you know it is notis busy, even when you know it is not

Sending modem and receiving modem Sending modem and receiving modem take a long time to negotiate the take a long time to negotiate the connectionconnection

Potential Modem Potential Modem Problems (Problems (continuedcontinued)) During a connection, it sounds as if During a connection, it sounds as if

handshaking starts all over againhandshaking starts all over again

File transfers are slowFile transfers are slow

Modem loses connection at odd Modem loses connection at odd times or is slowtimes or is slow

Modem drops the connection and Modem drops the connection and gives NO CARRIER messagegives NO CARRIER message

Potential Modem Potential Modem Problems (Problems (continuedcontinued)) When weather is bad, connection often When weather is bad, connection often

disconnectsdisconnects

When large files are downloaded, some When large files are downloaded, some data is lostdata is lost

Connection fails when large files are Connection fails when large files are uploaded or downloadeduploaded or downloaded

Nothing but garbage across the Nothing but garbage across the connectionconnection

Troubleshooting Troubleshooting ModemsModems

How Dial-up How Dial-up Networking WorksNetworking Works

Creating a Dial-up Creating a Dial-up Networking Networking ConnectionConnection Windows XPWindows XP

– Network Connections applet in Control Network Connections applet in Control PanelPanel

Windows 2000Windows 2000

– Network and Dial-up Connections applet Network and Dial-up Connections applet in Control Panelin Control Panel

Windows 9xWindows 9x

– Dial-up Networking and Network Dial-up Networking and Network Connection applets in My ComputerConnection applets in My Computer

Creating a Dial-up Creating a Dial-up Connection in Windows Connection in Windows 2000/XP2000/XP

Using Windows XP, launch New Using Windows XP, launch New Connection WizardConnection Wizard

Configure connection using Configure connection using Properties window of the Properties window of the connection iconconnection icon

Dial-up Networking Dial-up Networking ProblemsProblems Cannot make a connectionCannot make a connection

Can connect, but get message Can connect, but get message “Unable to resolve hostname…”“Unable to resolve hostname…”

After connecting, get error message After connecting, get error message “Unable to establish a compatible set “Unable to establish a compatible set of network protocols”of network protocols”

When double-click Web browser, When double-click Web browser, modem does not dial automaticallymodem does not dial automatically

DSL and Cable Modem DSL and Cable Modem ConnectionsConnections Broadband technologies Broadband technologies

– Support transmission of more than one Support transmission of more than one kind of data at oncekind of data at once

TCP/IP settings usually the same as TCP/IP settings usually the same as modem-to-phone line connectionmodem-to-phone line connection

Use a network card in the PC for Use a network card in the PC for physical connection to networkphysical connection to network

Installation of DSL and Installation of DSL and Cable Modem Internet Cable Modem Internet ConnectionsConnections1.1. Install network card and drivers to control Install network card and drivers to control

itit

2.2. Use network cable to connect PC to cable Use network cable to connect PC to cable modem or DSL boxmodem or DSL box

3.3. Install TCP/IP and bind TCP/IP to the cardInstall TCP/IP and bind TCP/IP to the card

4.4. Configure TCP/IP to connect to Internet or Configure TCP/IP to connect to Internet or LANLAN

5.5. Install application software (eg, browser) Install application software (eg, browser) to use the connectionto use the connection

Cable ModemCable Modem

DSL and ISDN ServiceDSL and ISDN Service

Provided by local telephone companyProvided by local telephone company

Uses DSL/ISDN converter box, Uses DSL/ISDN converter box, sometimes combined with a routersometimes combined with a router

DSL uses a DSL routerDSL uses a DSL router

– ISDN connection uses Terminal Adapter ISDN connection uses Terminal Adapter (TA) or ISDN router(TA) or ISDN router

Sharing Internet Sharing Internet ConnectionsConnections

One computer on the LAN with direct One computer on the LAN with direct connection to Internet can serve as host connection to Internet can serve as host computer for others on the LAN (ICS) – computer for others on the LAN (ICS) – Internet Connection SharingInternet Connection Sharing

For broadband connections, broadband For broadband connections, broadband converter box can connect to network device converter box can connect to network device that manages connection for entire networkthat manages connection for entire network

Router can serve as a wireless access point Router can serve as a wireless access point for computers to connect wirelessly to for computers to connect wirelessly to InternetInternet

Sharing Internet Sharing Internet Connections – Connections – (Continued)(Continued)

Internet Connection Sharing (ICS) enables a Windows computer to share its Internet connection with computers on local area networks. It's been around since Windows 98 SEWindows 98 SE, and with the launch of Windows XP, it's only gotten better

Windows XP ICS has some notable advantages over the versions of ICS in Windows 98 Second Edition and Windows Me:

It's easier to set up. There's no software to install, and it doesn't add any network components or protocols

It's much more reliable and much less likely to cause network problems

Sharing Internet Sharing Internet Connections – Connections – (Continued)(Continued)

Windows XP ICS has some notable advantages over the versions of ICS in Windows 98 Second Edition and Windows Me: (Continued)

You can create a Network Bridge connecting two or more local area networks and share the Internet connection with the computers on all of them. This is especially useful if your XP computer is connected to both a wired and wireless network

ICS client computers can use XP's Internet Gateway to monitor and control the server computer's Internet connection. If you have a dial-up connection, you can connect and disconnect when deciding whether to enable ICS

Sharing Internet Sharing Internet Connections – Connections – (Continued)(Continued)

Consider these points when deciding whether to enable ICS

WARNING #1:WARNING #1: When you enable ICS, the network adapter connected to the local area network is assigned a static IP address of 192.168.0.1. The client computers are assigned other IP addresses in the 192.168.0.x range. These addresses may not be compatible with an existing network

WARNING #2:WARNING #2: Don't enable ICS if any computer in your network is configured as a domain controller, DHCP server, or DNS server. Don't enable it if another computer is running ICS or Network Address Translation (NAT)

WARNING #3:WARNING #3: To enable ICS, you must be logged on as a user that is a member of the Administrators group

WARNING #4:WARNING #4: If you establish a Virtual Private Networking (VPN) connection while sharing a different connection, the client computers won't be able to access the Internet until the VPN connection is ended

Sharing Internet Sharing Internet Connections – Connections – (Continued)(Continued)

Preparing for ICS The ICS server computer must have two network connections: one for the Internet, and one for the local area network. The Internet connection may be a dial-up (PPP or ISDN), cable modem, DSL, or other broadband Ethernet connection. The LAN connection may be a wired, wireless, or even a USB Ethernet connection. Before enabling ICS:

Set up your Internet connection and test it so that you know you can connect to the Internet

Decide whether to allow client computers to control the server's Internet connection using the Internet Gateway. This feature is automatically available on clients running Windows XP. On clients running Windows 98, Windows 98 Second Edition, or Windows Me, you must run XP's Network Setup Wizard to enable the gateway. If you have a Windows XP CD-ROM, you can run the Wizard from it. Otherwise, create a network setup disk containing the Wizard files

Implementing a Implementing a FirewallFirewall Filters data packets, ports, Filters data packets, ports,

applications, and informationapplications, and information

Hardware firewallsHardware firewalls

Software firewallsSoftware firewalls

Hardware FirewallsHardware Firewalls

Software FirewallsSoftware Firewalls

Supporting Internet Supporting Internet ClientsClients Web browsersWeb browsers

EmailEmail

FTP (File Transfer Protocol)FTP (File Transfer Protocol)

Supporting Web Supporting Web BrowsersBrowsers Addresses that Web browsers use to Addresses that Web browsers use to

locate resources on a Web server locate resources on a Web server (Uniform Resource Locator)(Uniform Resource Locator)

Ensuring privacy with HTTPS and Ensuring privacy with HTTPS and SSLSSL

Troubleshooting common problems Troubleshooting common problems that occur with Web browsersthat occur with Web browsers

URL Structure URL Structure

Top-Level Domain Top-Level Domain NamesNames

Ensuring Privacy Ensuring Privacy Between the Web Server Between the Web Server and Browserand Browser

Configuring a BrowserConfiguring a Browser

Internet ExplorerInternet Explorer

– Internet Options windowInternet Options window

Netscape NavigatorNetscape Navigator

– Edit - PreferencesEdit - Preferences

Configuring a Browser Configuring a Browser ((continuedcontinued))

Configuring a Browser Configuring a Browser ((continuedcontinued))

Solving Browser Solving Browser Performance ProblemsPerformance Problems Clean up hard drive (Defrag, ScanDisk)Clean up hard drive (Defrag, ScanDisk)

Optimize system settings (System Optimize system settings (System Information)Information)

Clear browser cache and Web page historyClear browser cache and Web page history

Suppress image downloadsSuppress image downloads

Download browser updates and patchesDownload browser updates and patches

Supporting EmailSupporting Email

Supporting Email Supporting Email ((continuedcontinued))

Supporting FTP-File Supporting FTP-File Transfer ProtocolTransfer Protocol

Used to transfer files between two Used to transfer files between two computers using the same or different computers using the same or different operating system(s)operating system(s)

Both computers must have FTP installedBoth computers must have FTP installed

Can be executed from user-friendly GUI Can be executed from user-friendly GUI software or from a command promptsoftware or from a command prompt

FTP from a Command FTP from a Command PromptPrompt

File Transfer Using FTPFile Transfer Using FTP

File Transfer Using FTP File Transfer Using FTP ((continuedcontinued))