Servers and Workstations

The word server can refer to both the hardware and software or just the software that performs the service, such as File Transfer Protocol (FTP). Workstation refers to any local area network (LAN) host (a computer) that enables a user to interface with LAN resources.

Servers

Servers are computers in a network that are shared by multiple users. The server serves the required or requested information to the user's client. Following is a list of the more common server types found in networks:

• Application servers computers in a network environment that perform the necessary data operations to process and deliver information for clients.

• File servers computers in a network that act like remote disk drives in that they store programs and data files shared by users. The difference between a file server and an application server is that the file server stores programs and data, and the application server runs the programs and processes the data.

• Intranet servers computers dedicated to providing Internet-like services to private network users (such as hosting a corporate intranet).

• Mail (SMTP/POP) servers computers in a network that store incoming mail for distribution and forward outgoing mail.

• Network access servers computers in a network dedicated to authenticating users who log on. (Authentication is the process of verifying that users are who they say they are, similar to a person "showing ID." Authentication does not play a role in a user's access rights to a system, however.)

• Remote Access Servers work much the same as Network Access Servers with the exception that remote access users, such as remote dial, virtual private network (VPN) dial, and so on, are verified and/or authenticated.

• Print servers computers (or other dedicated hardware devices) in a network that controls one or more printers. Print servers enable printers to be located anywhere on a network and remain accessible to users on that network.

• Proxy servers computers that serve as a liaison between a sender and receiver. All input is received on one port and forwarded out a different port, closing a straight path between two networks and preventing intruders from accessing a private network. Proxy servers are one way to build a firewall between public and private networks.

• Terminal servers computers used to connect multiple dumb terminals to a network or host computer. (Dumb terminals are output devices such as display monitors that have no processing capabilities, but only accept data from the CPU and display it to the user.)

• Web servers computers that provide World Wide Web services on the Internet. If a Web server is used internally and not by the public, it is known as an intranet server.

Cisco Note

The Cisco LocalDirector series offers a solution that balances user traffic load across multiple Transmission Control Protocol/Internet Protocol (TCP/IP) application servers, such as a WWW or FTP server. Cisco LocalDirector tracks network sessions and server load conditions in real time, directing each session to the most appropriate server. All physical servers appear as one virtual server, requiring only a single IP address and URL for an entire server farm. More information about LocalDirector can be found at www.cisco.com/warp/public/cc/pd/cxsr/400/.

Server Platforms

Table 4-1 shows you various server hardware with their associated central processing units (CPUs) and Network Operating Systems (NOSs).

Table 4-1. Server Platforms (Abridged, Source: Computer Desktop Encyclopedia, 2001, The Computer Language Co., Inc.)

Server Hardware	CPU & NOS
Intel (x86)	Lantastic-DOS NetWare OS/2-Lan Manager/Server Microsoft Windows NT, 2000, XP Solaris (UNIX) AIX (UNIX) SCO Open Server (UNIX) SCO UltraWare (UNIX) NeXTStep (UNIX) VINEs (UNIX) Interactive UNIX
Sun SPARCserver	Solaris (UNIX)
Motorola 680x0	Mac OS A/UX (UNIX)
PowerPC	Mac OS AIX (UNIX)
Unisys (x86) NCR (x86)	UNIX SVR4
IBM System/390 zSeries	MVS VM DS/390 ZOS
IBM RS/6000 pSeries	AIX (UNIX)
IBM AS/400 iSeries	OS/400
Compaq Alpha	Digital UNIX OpenVMS Windows NT
DEC VAX	VMS Ultrix (UNIX) Pathworks
HP (PA-RISC)	HP/UX (UNIX) MPE/ix (UNIX)
Tandem (MIPS)	NonStop Kernel

Clients and Workstations

Clients and LAN workstations are any host enabling a user to access and use network resources. Clients can be classified as any hardware or software that makes a request from a server, such as a file transfer request from a file server or a URL request from an intranet/Internet server.

Table 4-2 details the client hardware with associated CPU and operating system (OS) implementations.

Table 4-2. Client Platforms (Abridged, Source: Computer Desktop Encyclopedia, 2001, The Computer Language Co., Inc.)

Client Hardware	CPU & OS
Intel (x86)	Windows 3.1, 95/98, NT, 2000, ME and XP
Sun SPARCstation	Solaris (UNIX)
Motorola 680x0	Mac OS A/UX (UNIX)
PowerPC	Mac OS AIX (UNIX)
HP 9000 (PA-RISC)	HP/UX (UNIX)
IBM RS/6000	AIX (UNIX)
Silicon Graphics (MIPS)	IRIX (UNIX)
Compaq Alpha	Digital UNIX OpenVMS Windows NT
DEC VAX	VMS Ultrix (UNIX)