Hardware Reference
In-Depth Information
Figure 17.1. The components of a client/server LAN.
A dedicated server computer often has faster processors, more memory, and more storage space than
a client because it might have to service dozens or even hundreds of users at the same time. High-
performance servers typically use from two to eight processors (and that's not counting multicore
CPUs), have many gigabytes of memory installed, and have one or more server-optimized network
interface cards (NICs), RAID (Redundant Array of Independent Disks) storage consisting of multiple
drives, and redundant power supplies. Servers often run a special network OS—such as Windows
Server, Linux, or UNIX—that is designed solely to facilitate the sharing of its resources. These
resources can reside on a single server or on a group of servers. When more than one server is used,
each server can specialize in a particular task (file server, print server, fax server, email server, and
so on) or provide redundancy (duplicate servers) in case of server failure. For demanding computing
tasks, several servers can act as a single unit through the use of parallel processing.
A client computer typically communicates only with servers, not with other clients. A client system is
a standard PC that is running an OS such as Windows. Current OSs contain client software that
enables the client computers to access the resources that servers share. Older OSs, such as Windows
3.x and DOS, required add-on network client software to join a network.
Peer-to-Peer Networks
By contrast, on a peer-to-peer network, every computer is equal and can communicate with any other
computer on the network to which it has been granted access rights. Essentially, every computer on a
peer-to-peer network can function as both a server and a client; any computer on a peer-to-peer
network is considered a server if it shares a printer, a folder, a drive, or some other resource with the
rest of the network. This is why you might hear about client and server activities, even when the
discussion is about a peer-to-peer network.
Peer-to-peer networks can be as small as two computers or as large as hundreds of systems and
devices. Although there is no theoretical limit to the size of a peer-to-peer network, performance,
security, and access become a major headache on peer-based networks as the number of computers
