bill@napier, 2001 bill/nos.html Networking Operating Systems (CO32010) 1. Operating Systems 2. Processes and scheduling 3

bill@napier, 2001http://www.soc.napier.ac.uk/~bill/nos.html

Networking Operating Systems (CO32010)

1. OperatingSystems

2. Processesand scheduling

3. Distributedprocessing

4. Distributedfile systems

5. Routingprotocols6. Routers

7. Encryption

8. NT, UNIX and NetWare

1.1 Introduction1.2 Multitasking and threading1.3 Example operating system components1.4 Exercises1.5 Example operating systems

Objectives:• To define some of the basic terminology of operating systems.• To define the main components of a network operating system.• To define the differences in operating systems.• To outline the history of some of the most used operating

systems.


Hardware, Operating Systems and User Interfaces

User interface:• Microsoft Windows (Windows 95/98/NT/2000).• Microsoft Windows 3.1.• X-Windows.

User interface:• Microsoft Windows (Windows 95/98/NT/2000).• Microsoft Windows 3.1.• X-Windows.

Operating system:• Microsoft Windows (Windows 95/98/NT/2000).• DOS.• UNIX/Linux.• VMS.• Novell NetWare.

Operating system:• Microsoft Windows (Windows 95/98/NT/2000).• DOS.• UNIX/Linux.• VMS.• Novell NetWare.

Hardware:• x86 architecture.• SPARC architecture.• Apple architecture.

Hardware:• x86 architecture.• SPARC architecture.• Apple architecture.


Operating System

Printer Printer ServerPrint Queues

Volumes

User account database

Resources

KernelKernel

Groups

Users

File system

Memory

Operating system

Hardware, Operating Systems and User Interfaces


Operating system characteristics

Single-user Multi-user

Stand-alone Networked

Single-tasking Multitasking

Single processor Multi-processor


Operating Systems

Hardware

MicrosoftWindows95/98 (OS)

UnixLinux

DOSMac OS

MicrosoftWindowsNT (OS)

File system:- Creating a file system- Copying/deleting/moving files

Multi-user- Allowing users to login into system- Allows users permissions to certain resources- Manage queues for resources

Memory:- Creating virtual memory systems- Disk swapping for memory

Multiprocessing- Allowing several processes to run, at a time- Scheduling of processing to allow priority

Device interfacing:- Access to connected devices- Multi-user access- Device drivers

Networking:- Remote login/file transfer- Creating global file systems


Mouse driver

Video driver

Soundcard driver

Operating System

Network driver

Application program

Applicationprogram

Kernel

Communicationwith operating system

Keyboard driver

Operating SystemComponents


Information passed between processes

Low-levelinterrupt

Low-levelinterrupt

ProcessProcess

Low-levelinterrupt

Low-levelinterrupt

ProcessProcess

Message or signal

Network or local computer

Data passed between processes

Interrupt Interrupt

Low-levelinterrupt

Low-levelinterrupt

ProcessProcess

Low-levelinterrupt

Low-levelinterrupt

ProcessProcess

Message or signal

Network or local computer

Data passed between processes

Interrupt Interrupt


Preemptive Multitasking

Processor Okay No.1, you’ve had your turn,

get to the back ofthe queue. Next!

Okay No.1, you’ve had your turn,

get to the back ofthe queue. Next! Process queue

23 4 5

1

Come on. My turn soon

Come on. My turn soon

Pre-emptive multitasking:Processes are given some time on the processor. This allows all the processes to have some time on the processor, and makes for smoother and more reliable operation


Co-operative Multitasking

Sorry. You’ll have towait until he’s

finished

Sorry. You’ll have towait until he’s

finished

6

Process queue

2 3 4 5

Processor

1

Hurry up. I’mwaiting. You’ve

been on that processorfor ages.

Hurry up. I’mwaiting. You’ve

been on that processorfor ages.

This isn’tvery fair!

This isn’tvery fair!

Hurray. I could stay here forever.

Anyway, I’m not going back to

the end of the queue.

Hurray. I could stay here forever.

Anyway, I’m not going back to

the end of the queue.

Co-operative multitasking:Processes must yield from the processor, before other processes can run on the processor


Boilpotatoes

Boilpotatoes Microwave

the pie

Microwavethe pie

Boilcarrots

Boilcarrots

Putpotatoeson plate

Putpotatoeson plate

Putpie

on plate

Putpie

on plate

Putcarrotson plate

Putcarrotson plate

Potatoesare soft

Carrotsare soft

Pie is cooked

Threads in a task


Threads

Process approach

Interlinkingof threads

Independentthreads

Threads approach

Process splits into threads

Process

Common sharingof data between threads

Splitting a process into threads


Dynamic Link Libraries

Dynamic link library (DLL)(standard ones stored in \WINDOWSand \WINDOWS\SYSTEM folders)- WINSOCK.DLL (TCP/IP)- GDI.DLL (Graphical interface)- KERNAL32.DLL (Kernel)

Program

Program calls upa DLL when it requires a certain function

Static libraryis used whencompiling theprogram. All theassociated codeis included in theprogram (even ifit is not used)


TCP/IP affected virus

TCP/IPDLL

(Virus effected)

TCP/IPDLL

(Virus effected)

Application program

Application program

TCP/IPDLL

(Correct version)

TCP/IPDLL

(Correct version)

Internet/network

Internet/network

Virus can nowlisten to (and modify) any networktraffic

Infected networktransmission (such asinfecting other users,typically from an e-mail list)


Window’s Components

• User. The User component provides input and output to and from the user interface. Input is from the keyboard, mouse, and any other input device and the output is to the user interface. It also manages interaction with the sound driver, timer, and communications ports.

• Kernel. The Kernel provides for core operating system components including file I/O services, virtual memory management, task scheduling and exception handling, such as: file I/O, exceptions, virtual memory management, task scheduling.

• GDI. Controls output to screen and printer.

User

GDI

Windows 95/98 core

Kernel


Virtual Machine Manager

VirtualMachineManager

VirtualMachineManager

Program 1

- Process scheduling- Memory paging- MS-DOS support

Program 3

Program 2

Programs have access toall the resources of the computer,as if they were the only program running

Creating virtualmemory (up to 2/4GB) DOS

program

DOSprogram

DOS emulator


Virtual Machine Manager

• Process scheduling. This is responsible for scheduling processes. It allows for multiple applications to run concurrently and also for providing system resources to the applications and other processes that run. This allows multiple applications and other processes to run concurrently, using either co-operative multitasking or pre-emptive multitasking.

• Memory paging. Windows 95/98/NT uses a demand-paged virtual memory system, which is based on a flat, linear address space accessed using 32-bit addresses. The system allocates each process a unique virtual address space of 4GB. The upper 2GB is shared, while the lower 2GB is private to the application. This virtual address space is divided into equal blocks (or pages).

• MS-DOS Mode support. Provides support for MS-DOS-based applications which must have exclusive access to the hardware. When an MS-DOS-based application runs in this mode then no other applications or processes are allowed to compete for system resources. The application thus has sole access to the resources.


Example: Windows NT Architecture

Hardware

Devicedriver

HAL (Hardware Abstraction Layer)

Microkernel

I/Omanager

Objectmanager

Processmanager

Localprocedure

callfacility

Virtualmemorymanager

Win32WindowManager

Graphicdevicedriver

Executive Services

NT Executive

Application

User mode

Kernel mode

Documents

bill@napier, 2001 bill/nos.html Networking Operating Systems (CO32010) 1. Operating Systems 2. Processes and scheduling 3