Transcript A+ Guide to Software, 4e - c-jump

A+ Guide to Software, 4e
Chapter 9
Windows on the Internet
The TCP/IP Suite of Protocols
• Client/server application
– Client application on one PC requests data from server
– Server application on another PC returns data
• Example: World Wide Web
– The client is a Web browser
– The server is a Web server; e.g., Apache HTTP server
– Requested data is a Web page
• Client applications are installed as programs
• Server applications are installed as services
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Using IP and Port Addresses to
Identify Services
• Port (port address, port number)
– Number that identifies server application to client
– Server application listens for request at assigned port
– Example: port 80 is typically assigned to Web servers
• Port numbers appear at the end of an IP address
– Example: 138.60.30.5:80
• A few other common ports and assigned services
– Port 20: FTP (File Transfer Protocol)
– Port 25: E-mail (using SMTP protocol)
– Port 443: Web server (using HTTPS protocol)
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Using IP and Port Addresses to
Identify Services (continued)
• Communication protocol
– Defines rules of communication between client/server
– Example: POP3 is used by client to receive e-mail
• Information flow between client and server
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Application sends request to OS
OS passes request to NIC
NIC places request on network
NIC on receiving end sends request to OS
OS passes request to Web server application
Web server responds by sending data to OS
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TCP/IP Protocol Layers
• TCP/IP suite lies between applications and the OS
• API: application programming interface
• How application protocols are used
– Application makes an API call to the OS
– The API causes OS to generate a request
• Request follows format specified by application protocol
– After response is passed back, a session is established
• Example involving HTTP (Hypertext Transfer Protocol)
– Web browser makes an API call to the OS
– OS makes an HTTP request for a browser
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TCP/IP Protocol Layers (continued)
• Transmission Control Protocol (TCP)
– A connection-oriented protocol
– Makes a connection, checks delivery, resends data
• User Datagram Protocol (UDP)
– A connectionless or best-effort protocol
– Does not guarantee delivery
• Internet Protocol (IP)
– Breaks up and reassembles data into packets
– Routes packets to their destination
• TCP uses IP to establish session and verify delivery
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TCP/IP Protocol Layers (continued)
• ARP (Address Resolution Protocol)
– Responsible for locating a host on a local network
• RARP (Reverse Address Resolution Protocol)
– Discovers Internet address of host on a local network
• ICMP (Internet Control Message Protocol)
– Communicates problems with a transmission
– Example: message deleted due to excessive hops
• Network protocols used by hardware
– Ethernet and PPP (Point-to-Point Protocol)
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TCP/IP Utilities
• TCP/IP component includes a group of utilities
– Location: Windows or \Winnt folder
• Commonly used utilities: Ping, Winipcfg, Ipconfig
• SNMP (Simple Network Management Protocol)
– Provides system management tools for networks
• Microsoft SNMP Agent
– Utility installed after TCP/IP is installed
– Used to monitor remote connections
• Tracert (trace route): shows hops along packet route
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Connecting to the Internet
• Broadband: supports multiple transmission types
• Internet Service Provider (ISP)
– Connects a PC or network to the Internet
• Bandwidth technologies used by ISPs:
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Regular telephone lines
Cable modem
DSL (Digital Subscriber Line)
ISDN (Integrated Services Digital Network)
Satellite access
Wireless access
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Cable Modem and DSL Connections
• Comparing communication media
– Cable modem: TV cables shared by multiple users
– DSL: dedicated phone lines
• Comparing service plans
– Both: sliding-scale residential and business plans
• Comparing setup
– Both: a modem interfaces PC and broadband jack
• Comparing installation services:
– Both: will install equipment at additional cost
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Cable Modem and DSL Connections
(continued)
• Overview of installing cable service or DSL
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Connect the PC to the cable modem or DSL box
Connect cable modem/DSL box to broadband jack
Plug up power and turn on the broadband device
Configure TCP/IP settings for connection to the ISP
Test connection by using a browser to surf the Web
• Devices and information needed for an installation
– A computer with an available network or USB port
– Modem/box and network cable
– TCP/IP settings
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Dial-Up Connections
• Based on a modem and regular phone line
• How dial-up networking works
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TCP/IP creates data packets for transport
PPP adds its own header and trailer to data packets
PPP presents packet to modem for delivery on line
Process is reversed when data packet is received
• Overview of setting dial-up in Windows XP
– Install an internal or external modem
– Launch New Connection Wizard
– Follow directions onscreen
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Dial-Up Connections (continued)
• A few troubleshooting tips
– Plug in a regular phone and check line for a dial tone
– Try another phone number
– Reboot your PC and try again
• Overview of setting dial-up in Windows 9x/Me
– Dial-Up Networking must first be installed
• A dial-up adapter will also be installed
– Install an internal or external modem
– Create connection with Make New Connection Wizard
– Configure the connection from Properties dialog box
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Figure 9-31 Two or more networked computers can share a
single Internet connection
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Implementing a Software Firewall
• Guidelines for protecting your PC
– Keep Windows updates current
– Use a software or hardware firewall
– Run antivirus software and keep it current
• Services provided by a hardware or software firewall
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Firewalls can filter data packets
Firewalls can filter ports
Firewalls can block certain activity within the network
Firewalls can filter inappropriate information
• Example of a software firewall: Windows Firewall
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Using a Router on Your Network
• Disadvantages of using a host to share a connection
– Host computer must always be turned on
– Only low-level security for your network
– Bottlenecks at host can slow traffic within network
• Solution: use a router to interface with the Internet
• Router provides two functions
– Takes place of host as gateway to the Internet
– Serves a hardware firewall to protect your network
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Installing and Configuring a Router
• Run the setup program on any network PC
• Connect the cable or DSL modem to the router
– Follow the instructions on the setup screen
• Connect PCs on your network to your router
– PC can connect directly to a network port
– You can also connect a switch or hub to the router
• Plug in the router and turn it on
• Sign in with default password and then reset it
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Installing and Configuring a Router
(continued)
• Configuring a router (using Linksys as an example)
– Access configuration program on router firmware
• Enter the IP address of the router (192.168.1)
– View and/or change default settings in Setup window
• Configure a hardware firewall
– Settings in Security tab and Access Restrictions tab
• Port filtering: open or close certain ports for use
• Port forwarding
– Request to certain ports forwarded to certain PCs
– Local PC must have static address for this service
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Virtual Private Network
• How VPN security works
– Remote user sends id to authentication server
– Authentication server encrypts data
• Various encryption protocols are used; e.g., CHAP
– Tunnel is created so all data transferred is encrypted
• Various tunneling protocols are used; e.g., PPP
• How to configure a router to support VPN
– Select encryption and tunneling protocols
– Configure each tunnel the VPN will support
• Configure client for VPN from Network Connections
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Supporting Internet Clients
• Section task: support Internet clients
• Common Internet clients
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Web browsers
E-mail
FTP
VoIP
Windows XP Remote Desktop
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Supporting Web Browsers
• Web page: text file with an .htm or .html extension
– Coded in HTML (Hypertext Markup Language)
• Web browser: requests pages from a Web server
• Uniform Resource Locator (URL): Web page address
• Components of a URL
– Protocol, host name, network name, folder, file name
– Domain name = host name + network name
– Example: http://www.course.com/myfolder/myfile.html
• Name resolution service relates name to IP address
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Figure 9-49 A URL contains the protocol used, the host name of the Web
server, the network name, and the path and filename of the requested file
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Table 9-3 Suffixes used to identify top-level domain names
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Supporting Web Browsers (continued)
• Solving Internet Explorer problems
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First perform routine maintenance; e.g., run ScanDisk
Clean out cache that IE uses to hold temporary files
Suppress downloading images
Repair a corrupted Internet Explorer cache
Run antivirus software
Update Internet Explorer
Verify Windows system files using System File Checker
Remove and reinstall Internet Explorer 6
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Supporting Web Browsers (continued)
• Digital certificate: identification plus public key
• SSL (Secure Sockets Layer)
– Encryption system using a digital certificate
– Data is encrypted with public key
– Data is decrypted with a private key
• TLS (Transport Layer Security)
– An improved version of SSL
• HTTPS (HTTP secure)
– Can mean HTTP over SSL or HTTP over TLS
– Indicates secure protocol being used is SSL or TLS
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Supporting E-mail
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SMTP: Simple Mail Transfer Protocol
SMTP AUTH (SMTP Authentication): improved SMTP
POP: Post Office Protocol
IMAP4: Internet Message Access Protocol, version 4
Route traveled by e-mail
– Client sends e-mail to client e-mail server using SMTP
– Client e-mail server sends e-mail to recipient with SMTP
– Recipient’s e-mail server forwards e-mail to recipient
• Recipient’s e-mail server uses POP or IMAP4
• Recipient must first login and request e-mail from server
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Supporting FTP
• File Transfer Protocol (FTP)
– Used to transfer files between two computers
• FTP server (or FTP site)
– Application running on another server; e.g., Unix server
• FTP from a command prompt
– Connection to a network must first be established
– Some commands: FTP, get yourFile.dat
• File transfer using FTP software
– FTP utility software: can be downloaded from Internet
– Web browser: change protocol used in address bar
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Supporting VoIP
• VoIP (Voice-over-IP)
– Provides voice communication over a network
• Two types of phones used in VoIP service
– Digital telephone: plugs into a network port
– Analog phone: needs Analog Telephone Adapter (ATA)
• Special requirements of VoIP
– Phones must be assigned number by VoIP provider
– Phones are programmed to use dynamic IP addressing
– Each network cable to phone needs a ferrite clamp
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Figure 9-75 The desktop of the remote computer is available on
your local computer
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