Chapter 8 Web Server Hardware and Software Web

Chapter 8: Web Server Hardware and Software

Web Server Basics • The main job of a Web server is to respond to requests from Web client computers • There are 3 components of a Web server: – Hardware – Operating system software – Web server software 2

Types of Web Sites • Development sites: Used to evaluate different Web designs • Intranets: Corporate networks that house internal memos, corporate policy handbooks, and a variety of other corporate documents • Extranets: Intranets that allow authorized parties outside the company to access information stored in the system • Transaction-processing sites: Commerce sites that must be available 24 hours a day, seven days a week • Content-delivery sites: Deliver content such as news, histories, summaries, and other digital information 3

Web Clients and Web Servers • Client/server architectures – Client computers request services – A server processes the clients’ requests • Web software is platform neutral, meaning that it lets different types of servers communicate with a variety of clients 4

Electronic Mail (E-Mail) • We all know the benefits of email • Email drawbacks include: – Time spent by business people responding to e-mail – Computer viruses • Programs that attach to other programs • Can cause damage when the host program is activated – Spam 5

Spam • Spam is unwanted e-mail • During one 24 -hour period in 2005 researchers estimated that 106 billion spam e-mail messages were sent 6

7

Solutions to the Spam Problem • Reduce the possibility that a spammer can automatically generate e-mail addresses • Control exposure of an e-mail address • Use multiple e-mail addresses • Content filtering strategy – Requires software that identifies content elements that indicate if a message is (or is not) spam 8

Solutions to the Spam Problem • Content-filtering techniques – Black list spam filter • Looks for known spammer From addresses in incoming messages – White list spam filter • Examines From addresses and compares them to a list of known good sender addresses – Challenge-response technique • Compares all incoming messages to a white list 9

Web Site and Internet Utility Programs • Finger – Runs on UNIX operating systems – Allows users to obtain information about other network users – Command yields a list of users who are logged on to a network • Ping (Packet Internet Groper) – Tests connectivity between two computers connected to the Internet 10

Tracert and Other Route-Tracing Programs • Tracert (TRACE Rou. Te) – Sends data packets to every computer on the path between one computer and another – Clocks packets’ roundtrip times – Calculates and displays the number of hops between computers – Calculates the time it takes to traverse an entire one-way path between machines 11

Telnet and FTP Utilities • Telnet – Through Telnet, an administrator or another user can access someone else's computer remotely. • File Transfer Protocol (FTP) – The File Transfer Protocol (FTP) is a standard network protocol used to transfer computer files between a client and server on a computer network. 12

Data Analysis Software • Web servers can capture: – Data about who is visiting a Web site – How long the visitor’s Web browser viewed the site – Date and time of each visit – Which pages a visitor viewed • Data captured by Web servers are stored in a log file 13

Link-Checking Utilities • Link checker examines each Web page and reports on URLs that: – Are broken – Seem broken – Are incorrect in some way • Orphan file – File on a Web site not linked to any page • Dead link – When clicked, it displays an error message rather than a Web page 14

Remote Server Administration • Web site administrator can control a Web site from any Internet-connected computer • Net. Mechanic – Offers a variety of link-checking, HTML troubleshooting, site-monitoring, and other programs 15

Web Server Hardware • Web server computers – More memory, larger hard disk drives, and faster processors than typical PCs • Blade servers – Placing small server computers on a single computer board, then installing boards into a rack-mounted frame • Virtual server (virtual host) – Maintains more than one server on one machine 16

Web Server Performance Evaluation • Benchmarking – Testing used to compare the performance of hardware and software • Throughput – Number of HTTP requests that a hardware and software combination can process in a unit of time • Response time – Time required by a server to process one request 17

Web Server Hardware Architectures • Server farms – Large collections of servers • Centralized architecture – Uses a few very large and fast computers • Distributed/decentralized architecture – Uses a large number of less powerful computers – Divides the workload among them 18

Load-Balancing Systems • Load-balancing switch – Piece of network hardware that monitors the workloads of servers attached to it – Assigns incoming Web traffic to a server that has the most available capacity at that instant in time 19

20