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  Microsoft(R) Product Support Services Application Note (Text File)
            WG0667: PEER-TO-PEER VS. CLIENT-SERVER NETWORKS
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                                                  Revision Date: 10/92
                                                      No Disk Included

The following information applies to Microsoft Windows(TM) for
Workgroups version 3.1.

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        A COMPARISON OF CLIENT-SERVER AND PEER-TO-PEER NETWORKS
        -------------------------------------------------------

This application note discusses the differences between the peer-to-
peer and client-server networking models.

  NOTE: The text for this application note was taken from the Windows
  for Workgroups Resource Kit.

Part of a network's overall design includes a decision about how
network resources will be shared and managed. Early networks used
central file servers to manage access to shared files and printers.
These servers were often workstations dedicated to sharing resources
or running network file server-related applications (for example,
database engines). Examples of network operating systems (NOSs) that
support the central file server model include Microsoft LAN Manager
and Novell(R) NetWare(R). The peer-to-peer network model was developed
more recently. Network workstations in a peer-to-peer model can access
resources shared by another user and share resources on their local
workstations to allow access by other members of their workgroup.
Windows for Workgroups supports the peer-to-peer networking model.

The central file server model requires that all file sharing take
place on the LAN server itself. That is, if the file server is the
central repository of information, then all exchanges of information
between workstations on a LAN must first pass through the file server.
This model is commonly implemented in an environment where the
workstations don't have the processing power or the resources capable
of supporting networking server functionality. For example, the
workstations may not have enough memory or may have small-capacity
hard disks.

In the peer-to-peer networking model, each workstation (or at least
one workstation) in a file-transfer scenario acts as both a client and
a server. As a client, the workstation can access the network
resources shared by another workstation. This model is commonly
implemented in an environment where workstations have the processing
power and resources to provide network server functionality or where
the cost of dedicating a workstation as a server is prohibitively
high. The peer-to-peer model is more flexible than the central file
server model because a workstation can directly access the shared
resources of another workstation.

To illustrate the differences between the central file server model
and the peer-to-peer networking model, let's say two workstations,
Workstation A and Workstation B, want to share a document. The
document was created on Workstation A and resides on Workstation A's
hard disk.

In the central file server model, Workstation A must connect to the
server, place the document on the server's hard disk, then inform
Workstation B that the document is available. Workstation B can then
connect to the server and access the document left there by
Workstation A. In the meantime, unless Workstation A is working with
the specified document directly on the file server (that is, making
modifications to the version of the document that resides on the file
server), the version of the document that may reside on Workstation
A's hard disk will likely become out of sync with the version of the
document Workstation B is now using.

In the peer-to-peer networking model, Workstation A simply grants
Workstation B permission to access the directory where the files are
located on Workstation A's hard disk. Workstation B can then directly
connect to Workstation A and access the document. Another way to
provide Workstation B with the document that Workstation A created is
to have Workstation B give Workstation A access to a shared directory
on Workstation B. Then Workstation A can copy the document from its
hard disk to the shared directory on Workstation B--however, the
latter procedure suffers from the same scenario as the central file
server model where the versions of the documents may get out of sync.
Since both workstations are considered to be peers, both support
client and server functionality.

