September 15,
2000
Author: Tom Jelen and Russ King
Computer networks can range
from a simple peer-to-peer network to a more complex
client-server network. While a complicated network can generally
perform more advanced functions, it requires more involved
planning, particularly regarding the server application.
If you have a client-server network (see
Networks 101: Client-Server
Networks), you are probably using the server to share files
and printers, and you may also be using it to host a Web site or
e-mail. If you are, then you probably are using server
applications. If you aren't, then you need them. Servers are
designed for nearly every purpose imaginable, from simple e-mail
servers to more complicated application servers. Every
application will have specific server requirements, and is
typically designed to run on
Windows NT/2000,
Novell Netware, or
Linux. Many servers can run multiple applications to serve a
variety of needs. As your network grows, you will find uses for
a variety of specialized server applications. The following is
just a brief introduction to the most common types of server
applications.
File and Print Servers
File and print servers are typically combined on one server and
perform as part of the
network operating system. The file and printer servers
manage the storage of data and the various printers on the
network. These servers regulate and monitor access to these
resources.
The three most popular are:
Mail Servers
Mail servers manage local (within your network) and global
(Internet-wide) electronic messaging. The mail server you choose
should support the Internet standards such as POP3 and
SMTP. Sometimes they even incorporate entire groupware
solutions: managing calendars, contacts, group meeting
scheduling, and other operations.
There are many examples of mail servers, but the most popular
are:
List Servers
While many mail servers offer the capability to serve an e-mail
listserv or mass e-mail distribution, there are some servers
that handle those tasks exclusively.
Here are a few to look at:
Fax Servers
Fax servers manage fax traffic in and out of the network,
allowing multiple users to send and receive faxes without a fax
machine.
Most of the popular e-mail servers have fax servers that you can
buy and integrate into your system, so look there first. One
interesting note is that
Microsoft Small Business Server (basically their
BackOffice software for fewer than 30 users) includes a fax
server. However, they didn't include it in Windows 2000.
Some other examples of standalone fax servers are:
For a more thorough list of fax server software check out:
Dave Central's list.
Web Servers
Web servers allow Internet users to attach to your server to
view and maintain Web pages. Web browsers such as Netscape and
Internet Explorer request documents from the Web server
using standard protocols, and the Web server retrieves the
requested documents and forwards them on to the browsers. Web
servers support a variety of technologies including
CGI scripts, Active Server Pages, and secure connections to
extend the power beyond the basic
HTML code.
The two most popular Web servers are:
One interesting thing is that this field is primarily the domain
of Linux and Unix (with Apache). However, Microsoft has been
playing catch-up, and it is gathering support around its IIS
product.
Database Servers or Database Management Systems (DBMS)
Though not exactly a server, DBMS systems allow multiple users
to access the same
database at the same time. While this functionality is
typically built into database software (ex. Microsoft Access
allows concurrent connections to its databases), a larger
database or a database with many users may need a dedicated DBMS
to serve all the requests. Examples of these include:
Application Servers
Application servers have undergone many changes and have grown
in both quantity and variety with the growth of the Internet.
Basically, an application server acts as an intermediary to
information. Here is a typical situation:
- A client makes a request for information (often as a
database request).
- The application server passes that request on to the
application.
- The application processes the request and sends the
results to the application server that then returns the
results to the client.
- The client gets the results of their query without needing
to download the whole database to his or her workstation.
In many usages, the application server works with a Web server
and is called a Web application server. The Web application
server receives requests from a Web page then returns the
information in a new Web page based on the results and uniquely
created. The technology to do this typically involves the
Common Gateway Interface (CGI),
Microsoft's Active Server Pages (ASP), or
Java Server Pages (JSP).
Examples of application servers include:
Terminal Servers or Communication Server
Generally, a terminal server refers to a piece of hardware that
allows devices to be attached to the network without a need for
network cards. PCs, "dumb" terminals supporting just a mouse and
monitor, or printers can all be attached via standard ports, and
can then be managed by the
network administrator.
However, Microsoft has co-opted this term and changed it to fit
their purposes. A Microsoft Terminal Server is a program running
on its Windows NT 4.0 operating system that provides the
graphical
user interface of the Windows desktop to user terminals that
don't have this capability themselves. The latter include the
relatively low-cost Net PCs or "thin clients" that some
companies are purchasing as alternatives to the autonomous and
more expensive PC with its own operating system and
applications. In the past, Terminal Server required an entirely
different operating system version, but Microsoft has expanded
this capability to be a standard application in Windows 2000.
Proxy Servers
Proxy servers act as intermediaries between your network users
and the wide world of the Internet. Proxy servers perform a
number of functions:
- Masks your network users IP addresses
- Strengthens security by only allowing certain requests to
come through and by providing virus protection
- Caches Web page data for a given period of time to allow
for more rapid access
Examples of
proxy servers include:
Conclusion
The preceding list is only an introduction to common server
applications. With the amount of time and money thrown at the
Internet, many types of servers are springing up to fill every
conceivable need. Whether you need to start up an e-mail list,
or provide access to talk radio 24 hours a day, there is a
server for you. For a detailed examination of the various types
and competitors in each of these markets, we recommend visiting
the holy grail of server information:
ServerWatch.
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