Network Operating Systems (NOS) Lecture 1: Network Operating Systems (NOS) By: Adal ALashban

What is an Operating System (OS)? - A program that acts as an intermediary between a user of a computer and the computer hardware. - Is a software that manages computer hardware and software resources and provides common services for computer programs. - Operating systems form an essential component of the system software in a computer system. - Application programs usually require an operating system to function.

Goals of Operating System (OS) Operating system goals:  Execute user programs and make solving user problems easier. Make the computer system convenient to use. Use the computer hardware in an efficient manner.

2 kinds of a software: Application Software: - Word processors, database manager, compiler, web browser. System Software: - Operating system itself. - Bridges between the hardware and users.

Functions of Operating Systems (OS) - Resource management. - Memory management. - Device management: – Printer – Hard drive – display - Process management. - Processor management (CPU time).

Why OS was Born? Batch processing – Resident Monitor.

Time Sharing Using Operating Systems

In Operating Systems - Time-sharing operating systems schedule tasks for efficient use of the system and may also include accounting software for cost allocation of processor time, mass storage, printing, and other resources. - For hardware functions such as input and output and memory allocation, the operating system acts as an intermediary between programs and the computer hardware. - Operating systems can be found on almost any device that contains a computer—from cellular phones and video game consoles to supercomputers and web servers.

Examples of Operating Systems Examples of popular modern operating systems include: Android, BSD, iOS, Windows Phone, Linux, OS X, QNX, Microsoft Windows, and IBM z/OS. All these examples, except Windows, Windows Phone and z/OS, share roots in UNIX.

Networks Operating Systems - Network operating system (NOS): software that implements an operating system of some kind that is oriented to computer networking. - The network operating system is designed to allow shared file and printer access among multiple computers in a network.

NOS Characteristics - Network operating systems (NOSs) distribute their functions over a number of networked computers. - It adds functions that allow users to access shared resources concurrently. - Client systems contain specialized software that allows them to request shared resources that are controlled by server systems responding to a client request.

Differences Between PC and a NOS - The NOS enhances the reach of the client PC by making remote services available as extensions of the local operating system. - Although a number of users may have accounts on a PC, only a single account is active on the system at any given time. - NOS supports multiple user accounts at the same time and enables concurrent access to shared resources by multiple clients (multitasking and multiuser environment).

Multiuser, Multitasking, and Multiprocessor Systems - A NOS server is a multitasking system. the OS is capable of executing multiple tasks at the same time. - Some systems are equipped with more than one processor, called multiprocessing systems. - Multiprocessing systems are capable of executing multiple tasks in parallel by assigning each task to a different processor. - The total amount of work that the server can perform in a given time is greatly enhanced in multiprocessor systems.

NOS Server Hardware - NOS servers are large systems with additional memory to support multiple tasks that are all active, or resident, in memory at the same time. - Additional disk space is also required on servers to hold shared files and to function as an extension to the internal memory on the system. - Because a NOS depends on the continuous operation of its servers, the extra hardware components justify the additional expense.

Choosing a NOS The main features to consider when selecting a NOS include: Performance. Management and monitoring tools. Security. Scalability. Robustness/fault tolerance.

Networks Operating Systems: Where to use? NOS can be used in: Routers, switches and hardware firewall. PCs in Peer-to-peer networks. Client-server Architecture.

Scale(size) Based Network Classification: The basic types of networks are: PAN LAN MAN WAN Internet

Personal Area Network (PAN) - Computer network organized around an individual person. - PAN involves a computer, a cell phone ..etc - Using Bluetooth and USB often used to link this kind of networks. - Communication Technology: Wired Wireless (WPAN): (Bluetooth, infrared)

Local Area Network (LAN) - A local area network (LAN) is a privately owned network that operates within and nearby a single building like a home, office or factory. - The connection must be high speed and inexpensive. - Size: few kilometers.

Local Area Network (LAN) Advantages: - Easy to share. - Cost of LAN setup is low. Disadvantages: - Power. - Security. - Speed. - Covers limited area.

Metropolitan Area Network (MAN) - A metropolitan area network (MAN) is a high-speed network that connects local area networks in a metropolitan area. - It covers a city. - Examples: The cable television networks available in many cities.

Metropolitan Area Network (MAN) Advantages: - Efficiency and shared access. - All the computers residing in the same area have an equal chance to access the network. Disadvantages: - Costly. - Security problems. - slow.

Wide Area Network (WAN) - A wide area network (WAN) is a network that covers a large geographic area. - Such as a city, country, or the world) using a communications channel that combines many types of media. - Examples: The telephone lines, cables, and radio waves.

Wide Area Network (WAN) Advantages: - Increased efficiency. - Ease of communication. Disadvantages: - Security problems. - Training costs. - Maintenance problems.

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