Telecom OnLine: Lecture Mail

Welcome to Lesson 9, Day 1 - Chapter 8 - Simple Network Operations

Course Notes

Lesson 9 Notes

This chapter discusses networks and how they work - primarily through the use of operating system software.

Here's a great link for you to visit that gives an excellent and understandable overview of how network operating systems work:

How Operating Systems Work

Some background information . . .

In the early days of networking, the software used to communicate over the network was added on to the original operating system. True network operating systems, i.e., those designed specifically for networking, have only come into being very recently. MS LAN Manager and NetWare Lite are examples of this type of networking system.

Just so you'll know . . .

It is accepted in the industry to refer to a network operating system either as an N.O.S., or as a NOS (nôs, näs).

Network Operating Systems

As your text explains, without an operating system, a computer is just a pile of expensive metal and plastic. By the same token, without a network operating system, all you have is a bunch of computers and peripheral devices sitting out there working by themselves. In order to take advantage of the many resource enhancements networking provides, you have to have a way to manage all the components and make the various vendors' equipment work together - what the NOS makes happen.

What the NOS does . . .

http://www.tifb.state.tx.us/Handbooks/Wiring_Diagrams.htm

NOS Demands on the Hardware

Multitasking - supporting numerous processes at one time.

• Preemptive - The OS controls what process gets access to the CPU and for how long. Nearly all operating systems use preemptive multitasking, especially network operating systems.
• Cooperative - The OS does not have the ability to stop a process. Once that process has received control of the CPU it holds onto control until it is finished with whatever process it is doing.

Time slicing - Time slicing occurs when the computing cycles of a CPU are divided between tasks. Because of the speed of the CPU, it seems as though it is working on multiple processes at once, when in reality each process is started, processed for a certain number of cycles, then stopped while the CPU moves on to the next process.

General Functions of the NOS

• Connects all computers and peripheral devices on a network interactively into a whole unit
• Controls and coordinates the computers and devices
• Manages security and privacy on the network as well as on individual computers and authenticates user access to resources on the network
• Centrally manages resources and data
  

General NOS Components

• Naming Services - associate plain-language names to network addresses. Microsoft uses the NetBIOS naming system to identify network devices.
• Directory Services - A directory service like Microsoft’s Active Directory is a centralized database containing information on the network’s devices. Windows 2000 is the first Microsoft NOS that includes a comprehensive directory service – Active Directory. Novell NetWare has been using an equally effective directory service (called NDS) since NetWare version 4 was introduced in 1993.
• Client network software - the part of the NOS that is installed on machines accessed by users on the network. Allows users to take advantage of network resources.
• Server network software - the NOS installed on machines that will handle resources that will be accessed by clients on the network.
• Redirector - A software component of the NOS that is found on both the client and server operating systems. The redirector intercepts requests and determines if the local machine can process the request immediately. If so, it sends it to the local CPU for processing. If not, it sends it on to the server of the particular requested resource for processing. Also known as a requester in Novell and a shell in Linux.
• Designator - Another NOS software component that keeps track of the drive letters assigned to shared drives.

Lesson 9, Day 1 Assignment

You work for a small law firm in which each partner's secretary has always maintained case files on separated computers, and they have been shared by "sneakernet". In your Monday meeting this week, you suggested that the firm consider implementing a client-server network to make files and resources more accessible, and the firm, thus, more profitable. The partner's are intrigued by the idea, but have heard all the horror stories of how "the server crashed and now no one can get any work done, and we don't know how much data has been lost forever!!" What would you tell them about modern networking technologies that would help convince them and alleviate their fears?

Students to answer this case:

ASU -Anyone! Take a stab at it!

Remember to keep up with your on-line lessons and quizzes!

mdm