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Networks Defined
A connected group of systems that can share resources.

Resources include:

• Information
• Hardware, such as printers, scanners, or faxes.
• Software

Benefits
• Facilitates routine information exchange E-mail.
• WWW access
• Web Commerce
• GroupWare
• Share printers, plotters, CD-ROMs, scanners, fax machines, and other devices.

Local Area Networks (LANs) Defined
All systems:
located in the same area 
connected by a single cable system 

When two, or more, networks in the same general area are connected, it is called an internetwork . (Small i.)

When a LAN is connected to the global networking system, it is said to be part of the Internet . (Capital I.)

When multiple LANs, in multiple locations, are connected, it is called a Wide Area Network or WAN .

LANs are the building blocks of WANs  

The IEEE also defined a metropolitan area network or MAN. MANs use WAN technology to interconnect LANs within a specific geographical region.

All networks include certain common elements:

Software, Operating Systems and Protocols.
Media Cabling and Network Interface Cards (NICs) Hardware Servers , clients, and peripherals 

Network Software

Network operating system (NOS) software provides computers with basic client and server functionality. NT and Novell

Network Protocols provide the common methods or the rules through which information is exchanged.

Network Models

Peer to peer (Workgroup)
Each member computer can function as both a client and a server

Server based
Each computer specializes as either a client or as a server
Most widely used network model

Network Models Selection Criteria
In itself, a particular model is neither right nor wrong.
Models can only appropriate or inappropriate in application.
The appropriate model is the one that is suitable for the environment within which it exists.

Workgroup Characteristics

Inexpensive 
Easy to install
No dedicated servers or hierarchy
No centralized administration 
No network administrator
Accommodates 10 or less clients 

Windows for Workgroups, Win95, and NT Workstation all contain peer to peer functionality

Workgroup Environment

10, or fewer, users in the same area.
Limited growth projected. 
Security not a high priority.
Budget may be highest priority.


Server Based Network Model

Standard networking model.
Optimized i.e. dedicated to quickly servicing requests from network clients and ensuring the security of files and directories.
Centralized resource control.

Server Model Security Issues
Physical access.
User Accounts.

Centralized security database.

Passwords
Access control lists

Server Software
Certain Network Operating Systems (NOS), such as Novell, are optimized for file and print serving.
Other NOSs, such as NT, are optimized for application serving.


Specialized Servers

Application servers 
Communication servers 
Mail servers 
Fax servers
Web servers
Domain Controllers
Application Servers  

Server side of Client/Server Architecture
application services
processing services

SQL Server is an example of an application server

Communication Servers 

Provide a mechanism for users outside a network to access that network's resources.
Remote Access Server (RAS)

Domain Controllers/Directory Servers

Permit uses to locate, store, and secure information about a network and resources available from a network


File and Print Servers 

Provide network file services and access to networked printers. Enables users to centralize data while they run programs locally.


Fax Servers 

Receive incoming faxes via telephone and distributes them to their recipients over the network. Also handles outgoing faxes.

Web Servers 

Packages such as IIS facilitate Internet services i.e. web page serving, FTP, and Gopher services.

Mail Servers 

At a minimum, provide e-mail messaging for local clients. Can also provide 'store and forward' services. Exchange Server represents a sophisticated package for NT.  

Domain Controller

Manage a named collection of users, groups, and machines.
Controls user access to network resources.
Contains a security database that authenticates each user and assigns access privileges. 


Server and NOS

A network server and the network operating system work together as a unit. 


With the appropriate hardware, NT Server can take advantage of:

SMP
RAID
Clustering (Wolfpack)
Replication


Centralized Administration

Includes server based sharing of data and resources. 
A Security orientation mandates a server network model.
Ideally, a single password delivers all access. 


Hybrid Networks

Modern Microsoft Operating Systems such as WfWG, Win 95, and NT can function in either peer to peer or server based environments.
Sometimes these O/Ss are configured to exhibit the properties of both network models.


The Appropriate Model

Choose peer to peer when:

10 or fewer users.
All machines are relatively close.
Budget is a major priority and security isn't.
No specialized servers are needed


Choose server when:

More than 10 uses.
Centralized control or security is desired.
Specialized servers are needed.