Processing is shared among multiple small computers known as clients that are connected via a network to a host computer known as a server .
Clients - typically PCs, a type of high-powered small computer built for specialized applications called a workstation , or a network computer.
Server - typically dedicated to a specific type of processing, such as providing files with a file server, responding to database queries with a database server, or handling high-speed processing with an application server.
Because both the client and the server are capable of processing, processing is shared between the two computers depending on the capability of each.
Types of Servers Sends and receives faxes for entire organization Fax Sends and receives e-mail for entire organization Mail Handles requests for Web pages Web Handles high speed processing Application Handles queries to a large database and returns matching records Database Provides both software and data files to users File Purpose Server Type
Client/Server Advantages and Disadvantages Loss of client does not stop other clients from accessing server Upgrading system can be done in small steps System upgrades require that all clients and servers be upgraded regardless of location Servers can be specialized to one particular type of task Programming relationship between clients and servers is more complex Computing burden can be shared among servers and clients Disadvantages Advantages
It is possible to set up a peer-to-peer network, where each computer in the network is on the same level as other computers, and each computer is equally responsible for overseeing the functions of the network.
Any two computers in a peer-to-peer network may communicate directly with one another, or they may communicate through intermediate peer computers.
Peer-to-peer networks may be easier to setup, but are not as efficient as client/server networks.
Comparing Client/Server and Peer-to-Peer Networks
Network Standard: OSI Architecture Application Layer: User software (e.g. spreadsheet). Presentation Layer: Operating system functionality. Session Layer: Connection between user & network (e.g. logins). Transport Layer: Find best path for transmission. Network Layer: Routing (to which host, etc.) Data Link Layer: Error checking (parity, etc). Physical Layer: Packets on the media (T/P, Fiber, etc). Seven OSI Layers
The Internet’s TCP/IP Standard Application or Process Layer Internet Protocol (IP) Host-to-Host Transport Layer Network Interface Physical Layer Application Layer Presentation Layer Session Layer Transport Layer Network Layer Data Link Layer Physical Layer OSI Model
The physical layer sends packets over telephone lines, or other media, using packet switching.
Packet switching - individual packets are routed through the network based on the destination address contained in each packet. With packet switching, the same data path can be shared among many computers in the network, and if a computer on the network is inoperable, the packet finds another way to reach its destination.
A router is a special type of computer that has the sole purpose of accepting packets and determining the best way to send them to the destination computer--that is, the router specializes in switching the packets.
The sequence order allows the receiving computer to reconstruct the message.
Sending Data Between Computers on the Internet
Data Component Media 2 2 Source: Jerry Fitzgerald and Alan Dennis, Business Data Communications and Networking , 8th ed., p. 85, New York: John Wiley, 2005. Moderate Low- Moderate Moderate Satellite Moderate Low- Moderate Moderate Microwave Low Moderate Low Infrared Low Moderate Low Radio High - very High Very Low High Fiber Optics Low-high Low Moderate Coaxial Cable Low-high Low Low Twisted Pair Speed Error Rates Cost Media
Maximum Data Rates Leased lines used for commercial telecommunication 1.544 Mbps - 274 Mbps T-1 to T-4 Cable must support two-way communication; available in many locations but slows down as more people use it in a specific location As high as 55 Mbps but averages between 200 Kbps and 2 Mbps Cable Becoming more available. Does not slow down as more people sign up. 6 Mbps in; 640 Kbps out Digital Subscriber line (DSL) Available everywhere 56 Kbps Standard telephone service Comments Maximum Data Rate Transmission Method
Wireless LANs (WLANs) – replaces cabling with wireless transmissions that use radio frequencies to transmit information between individual computers
The individual computers do not communicate directly with each other; instead they communicate with a wireless network hub or router, which is also used to bridge the wireless network to traditional ethernet or provide a shared Internet connection.
Wi-Fi (for Wireless Fidelity) – also called IEEE 802.11b standard, the current popular standard for wireless networking supports data rate of 11 megabits/second, with a typical range through open air of about 220-1100 yards (200-1000 meters).
An e-mail address is composed of two parts: the user name and the server address .
The user name is assigned to a person or organization that is connected to a server, and it is separated from the server address by the at symbol (@).
Server address (a.k.a. domain name) – the IP address of the email host. The right-most part of the address is known as the top level domain .
Server addresses are easy-to-remember versions of the numeric IP addresses.
Top Level Domains www.ustreas.gov (U.S. Treasury Department) .gov Government www.netscape.net (Netscape) .net Network provider www.redcross.org (The Red Cross) .org Nonprofit organization www.ebay.com (eBay Auctions) .com Commercial company www.broadway.pro (Broadway theater shows) .pro Professionals* www.yourname.name .name Various* mhp.moscow.museum (Moscow House of Photography in Russia) .museum Museums* www.lanka.info (Information on Sri Lanka) .info Various* www.credit-cooperatif.coop (Crédit Coopératif Group in France) .coop Cooperatives* www.webmaster-resource.biz (Webmaster-Resource.biz, an e-commerce company) .biz Businesses* www.ba.aero (British Airways) .aero Aerospace organizations* www.usmc.mil (The U.S. Marine Corps) .mil Military www.uga.edu (The University of Georgia) .edu Educational institution Example Designation Type of Organization
Internet Operations Synchronously exchange electronic messages with other Internet users Internet Relay Chat Transfer text, images, video, and sound to your computer; search for information on Internet World Wide Web Work on a computer elsewhere on the Internet Telnet Participate in a wide variety of online discussion groups Newsgroups Download files (software, documents, or data) from or upload files to a server located on the Internet FTP Asynchronously exchange electronic messages with other Internet users E-mail Purpose Internet Operations
The Web is a special type of client/server network. To access the Web, the client computer uses software called a browser that initiates activity by sending a request to a Web server for certain information. The Web server responds by retrieving the information from its disk and then transmitting it to the client.
Browser – application layer software used for sending requests and displaying the results
Hypertext markup language (HTML) - tags in World Wide Web documents that are part of a special publishing language
Documents on the Web are referred to as Web pages, and their location is a Web site .
Web Pages vs. Physical Pages Can be created using word processor and printer Can be created with HTML and saved to a server Creation Can be linked only through a separate index Can be linked to other pages through hypertext Links to other pages Restricted to text and images Can include text, images, audio, and video information Types of information Restricted to single piece of paper Can extend beyond single screen Amount of information Ink on paper Electronic Form Physical Page Web Page Characteristics
Communication protocol used to transfer pages from Web server to browser
HTTPS is a more secure version
Uniform Resource Locator (URL)
Mnemonic Web address corresponding with IP address
Also includes folder location and html file name
http://www.amazon.com/gp/homepage.html Communication Protocol Domain Name Folder Path Web Page HTML File
Internet Protocols Display news group news Send outgoing e-mail mailto Download or upload files from an Internet FTP server ftp Log on to a remote computer connected to the Internet telnet Retrieve files from local hard disk file Retrieve Web pages http Purpose Protocol