In a paragraph, define throughput and response time. Explain why each is an important consideration ...

Answer to #1

Elements affecting overall server performance include hardware, operating system software, server software, connection bandwidth, user capacity, and type of Web pages being delivered. The number of users the server can handle is also important. This can be difficult to measure because both the bandwidth of the Internet connection and the sizes of the Web pages delivered can affect that number. Two factors to evaluate when measuring a servers Web page delivery capability are throughput and response time. Throughput is the number of HTTP requests that a particular hardware and software combination can process in a unit of time. Response time is the amount of time a server requires to process one request.

Answer to #2

The use of large collections of computers, especially powerful computers such as Web servers, requires significant amounts of electrical power to operate. Although much of this electrical power is used to operate the servers themselves, a substantial portion of it is used to cool the rooms in which the servers reside. Large computers generate tremendous amounts of heat.

Answer to #3

Although some Web server computers are housed in freestanding cases, most are installed in equipment racks. These racks are usually about 6 feet tall and 19 inches wide. They can each hold from five to ten midrange server computers. An increasingly popular server configuration involves putting small server computers on a single computer board and then installing many of those boards into a rack-mounted frame. These servers-on-a-card are called blade servers, and some manufacturers now make them so small that more than 300 of them can be installed in a single 6-foot rack.

Answer to #4

Web servers can capture visitor information, including data about who is visiting a Web site (the visitors URL), how long the visitors Web browser viewed the site, the date and time of each visit, and which pages the visitor viewed. This data is placed into a Web log file.

Answer to #5

E-mail headers and routing information, including the originating domain name and e-mail address, must be accurate and must identify the person who sent the e-mail. The use of deceptive e-mail headers is considered fraudulent and is viewed as a criminal offense.

Answer to #6

Legal solutions to the spam problem have achieved only limited success in reducing spam because it is expensive for governments to prosecute spammers. To become cost effective, prosecutors must be able to identify spammers easily (to reduce the cost of bringing an action against them) and must have a greater likelihood of winning the cases they file (or must see a greater social benefit to winning).
The best way to make spammers easier to find has been to make technical changes in the e-mail transport mechanism in the Internets infrastructure.

Answer to #7

The most common basic content-filtering techniques are black lists and white lists. A black list spam filter looks for From addresses in incoming messages that are known to be spammers. The software can delete the message or put it into a separate mailbox for review. A black list spam filter can be implemented at the individual, organization, or ISP level. Several organizations, such as the Spam and Open Relay Blocking System, collect black lists and make them available to ISPs and company e-mail administrators. Other groups, such as the Spamhaus Project, track known spammers and publish lists of the mail servers they use. Some of these are free services; others charge a fee. The biggest drawback to the black list approach is that spammers frequently change their e-mail servers, which means that a black list must be continually updated to be effective. This updating requires that many organizations cooperate and communicate information about known spammers.
A white list spam filter examines From addresses and compares them to a list of known good sender addresses (for example, the addresses in an individuals address book). A white list filter is usually applied at the individual user level, although it is possible to do the filtering at the organization level if the e-mail administrator has access to all individuals address books (some companies mandate such access for security purposes). The main drawback to this approach is that it filters out any incoming messages sent by unknown parties, not just spam. Because the number of false positives (messages that are rejected but should not have been) can be very high for white list filters, the rejected e-mails are always placed into a review mailbox instead of being deleted.

Answer to #8

E-mail attachments can be or can contain viruses. Using virus protection software and dealing with e-mailed security threats is a cost that comes with e-mail use.

Answer to #9

Apache HTTP Server has dominated the Web since it became widely available because it is free, performs efficiently, and has a large number of knowledgeable users who contribute technical advice to online discussion forums, wikis, and blogs. Apache runs on many operating systems (including FreeBSD-UNIX, HP-UX, Linux, Microsoft Windows, SCO-UNIX, and Solaris).
A number of companies sell support services for Apache for organizations that want the additional security; however, most Apache installations are supported by the organizations own technical staff using the free online help that is available.

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