Networking Operating Systems (CO32010) 1. Operating Systems 2. Processes and scheduling 3. Distributed processing 4. Distributed file systems 5. Routing protocols 6. Routers 7. Encryption 8. NT, UNIX and NetWare 1.1Introduction 1.2Multitasking and threading 1.3Example operating system components 1.4Exercises 1.5Example 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 Server Print Queues Volumes User account database Resources Kernel 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 Microsoft Windows 95/98 (OS) Unix Linux DOS Mac OS Microsoft Windows NT (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 Application program Kernel Communication with operating system Keyboard driver Operating System Components

Information passed between processes

Preemptive Multitasking Processor Okay No.1, you’ve had your turn, get to the back of the queue. Next! Okay No.1, you’ve had your turn, get to the back of the queue. Next! Process queue 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 to wait until he’s finished Sorry. You’ll have to wait until he’s finished 6 Process queue Processor 1 Hurry up. I’m waiting. You’ve been on that processor for ages. Hurry up. I’m waiting. You’ve been on that processor for ages. This isn’t very fair! This isn’t very 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

Boil potatoes Boil potatoes Microwave the pie Microwave the pie Boil carrots Boil carrots Put potatoes on plate Put potatoes on plate Put pie on plate Put pie on plate Put carrots on plate Put carrots on plate Potatoes are soft Carrots are soft Pie is cooked Threads in a task

Threads Process approach Interlinking of threads Independent threads Threads approach Process splits into threads Process Common sharing of data between threads Splitting a process into threads

Dynamic Link Libraries Dynamic link library (DLL) (standard ones stored in \WINDOWS and \WINDOWS\SYSTEM folders) - WINSOCK.DLL (TCP/IP) - GDI.DLL (Graphical interface) - KERNAL32.DLL (Kernel) Program Program calls up a DLL when it requires a certain function Static library is used when compiling the program. All the associated code is included in the program (even if it is not used)

TCP/IP affected virus TCP/IP DLL (Virus effected) TCP/IP DLL (Virus effected) Application program Application program TCP/IP DLL (Correct version) TCP/IP DLL (Correct version) Internet/ network Internet/ network Virus can now listen to (and modify) any network traffic Infected network transmission (such as infecting other users, typically from an 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.

Virtual Machine Manager Virtual Machine Manager Virtual Machine Manager Program 1 - Process scheduling - Memory paging - MS-DOS support Program 3 Program 2 Programs have access to all the resources of the computer, as if they were the only program running Creating virtual memory (up to 2/4GB) DOS program DOS program 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