Chapter 8:

Web Server Hardware and Software

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Web Server Basics

• The main job of a Web server computer is to respond to requests from Web client computers

• Three main elements of a Web server:

– Hardware

– Operating system software

– Web server software

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Server Connection

• WWW requests from the Client computer Browser are detected and handled on port 80 of the server.

• FTP requests on port 21 of the Server.• Mail on port 25• Telnet on port 23

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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

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Types of Web Sites (continued)

• Transaction-enabled sites– E-Commerce enabled sites (database, shopping

cart, payment processing capability).

– Examples: Web Catalog (e-store), Transaction Fee Model, Subscription Model, Auction Sites

• Content sites– Deliver content such as news, histories,

summaries, and other digital information.

– Examples: CNN.Com, IBM.com, Portals

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Static Content

• Static HTML Web pages – Static information

• File Extension: .html or htm

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Dynamic Content

• Dynamic content (DHTML) is nonstatic information constructed on a “Dynamic Webpage” in response to a Web client’s request. (Server-side Scripting)

Programs that create dynamic content use these File Extensions:

.asp – (Microsoft) - Active Server Pages .jsp – (Sun Microsystems) - Java Server Pages .php – (Apache Open Source) - Hypertext Preprocessor .cfm – (Macromedia) - ColdFusion

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Web Server Operating System

• Operating system tasks include running programs and allocating computer resources.

• Unix• Windows • Open-source software

– Developed by a community of programmers who make it available for download at no cost (Example- Linux)

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Web Server Software

The most popular Web Server programs are: – Apache HTTP Server (Open Source)

(JSP, PHP, CFM)

– Microsoft (Internet Information Server (IIS) or Microsoft Server 2008)

(ASP, .Net)

– Sun Java System Web Server (JSWS) (JSP)

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Application Servers

– Database Server – Manages Product Catalog, Customer database, etc.).

– Mail Server – Manages Internet e-mail

– Proxy Server – Controls access to main computer

– Ad Server – Maintains database of banner ads

– List Server – Creates and manages special e-mail lists.

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Spam – Phishing - Virus

• Spam – Any Unsolicited e-mail.

• Phishing – Amateur & Professional hackers attempting to obtain Personal Information or access to Content.

• Virus – Malicious Content

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Spam – Unsolicited E-Mail

Spam by the Numbers (2006)

Source: http://spam-filter-review.toptenreviews.com/spam-statistics.html

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Dealing With the Spam Problem

• Industry – Can reduce the likelihood that a spammer can automatically generate e-mail addresses

• User – Can control exposure of an e-mail address

• User – Can use multiple e-mail addresses

• User/Server – Can employ content filtering software

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Some Filtering Strategies

1. Black List spam filter

--Checks incoming messages against a known bad e-mail address list.

2. White List spam filter

--Checks incoming messages against a known good e-mail address list.

3. Challenge-Response technique--Forces a reply to all incoming messages not on a white

list.

4. Advanced Content Analysis

--Utilizes contextual filtering

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Server Firewalls

• Network Layer Firewall - Filter network traffic based on many packet attributes like IP Address, Domain name and destination port.

• Application Layer Firewall- inspect all packets for improper application content.

• Proxy Server – Can serve as a firewall by blocking unwanted content.

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Server Data Analysis Software

• Web Server Log File can capture:

– IP Address of Visitor

– Type of Request & Pages Viewed or Files Downloaded

– Date and time of each activity (timestamp)

– Status Code (successful, “404” error etc.)

– Type of browser viewed on

– Referrer URL (not always available)

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Server Log File

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Web Server Hardware Terms

• 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

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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

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Factors that can Influence Web Server Performance

There is always going to be a limit to the number of pages that a server can serve in a given time frame.

• Volume - Amount of Web Traffic (Hits)• Duty Cycle - No. of CPU-Intensive Operations• Capacity - Bandwidth Available

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More Web Server Hardware Terms

• 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

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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

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