Network operating systems, their composition and features. Operating systems: examples with descriptions. Examples of network operating systems

Until now, in the lectures of this course we have limited ourselves to the framework of classical operating systems, i.e. operating systems operating on autonomous single-processor computers, which by the mid-80s of the last century formed the basis of the world computer fleet. Subject to the criteria of increasing efficiency and ease of use, computing systems from this time on, which we already mentioned in the very first lecture, begin to rapidly develop in two directions: the creation of multiprocessor computers and the integration of autonomous systems into computer networks.

The advent of multiprocessor computers does not have a significant impact on the operation of operating systems. In a multiprocessor computing system, the content of the state changes execution. Not one process, but several, depending on the number of processors, can be in this state. Planning algorithms change accordingly. The presence of several executing processes requires more careful implementation of mutual exclusions during kernel operation. But all these changes are not ideological changes, they are not of a fundamental nature. Fundamental changes in multiprocessor computing systems affect the algorithmic level, requiring the development of algorithms for parallelizing problem solving. Since, from the point of view of our course, multiprocessor systems have not introduced anything fundamentally new into the development of operating systems, we will not consider them further.

The situation is different with computer networks.

Why are computers connected in networks?

Why was it necessary to connect computers in a network at all? What led to the emergence of networks?

One of the main reasons was the need to share resources (both physical and informational). If an organization has several computers and occasionally needs to print some text, then it does not make sense to buy a printer for each computer. It is much more profitable to have one network printer for all computers. A similar situation can arise with data files. Why keep the same data files on all computers, maintaining their coherence, if you can store a file on one machine, providing network access to it from all the others?
The second reason should be considered the possibility of speeding up calculations. Here, networked networks of machines successfully compete with multiprocessor computing systems. Multiprocessor systems, without essentially affecting the structure of operating systems, require quite serious changes at the hardware level, which greatly increases their cost. In many cases, it is possible to achieve the required speed of parallel algorithm calculations using not several processors within one computer complex, but several separate computers connected to a network. Such network computing clusters often have an advantage over multiprocessor complexes in the efficiency/cost ratio.
The next reason is related to increasing the reliability of computer technology. In systems where a failure can cause catastrophic consequences (nuclear energy, astronautics, aviation, etc.), several computer systems are installed in communication, duplicating each other. If the main complex fails, its work is immediately continued by the backup one.
Finally, the latest reason to appear (but for many the main reason) was the possibility of using computer networks for user communication. E-mails have practically replaced regular letters, and the use of computer technology to organize electronic or telephone conversations is confidently replacing regular telephone communication.

Network and distributed operating systems

In the first lecture, we said that there are two main approaches to organizing operating systems for computer systems connected to a network - these are network and distributed operating systems. It should be noted that the terminology in this area has not yet been established. In some works, all operating systems that ensure the functioning of computers on a network are called distributed, while in others, on the contrary, networked. We take the view that networked and distributed systems are fundamentally different.

IN network operating systems In order to use the resources of another network computer, users must be aware of its presence and be able to do so. Each machine on the network runs its own local operating system, which differs from the operating system of a stand-alone computer in the presence of additional network tools (software support for network interface devices and access to remote resources), but these additions do not significantly change the structure of the operating system.

FGOU SPO SPb TKUiK

Abstract on the subject “Informatics”

NETWORK OPERATING SYSTEMS

I've done the work

student of group 9GS-21

Dudarov Yuri

Saint Petersburg

1. Introduction

2.Network operating system

2.1 Peer-to-peer network OS and OS with dedicated servers

2.2 OS for workgroups and OS for enterprise networks

2.3 Signs of corporate OS

2.3.1.Support

2.3.2Help service

2.3.3 Security

3. Examples of SOS

1. INTRODUCTION

In order to understand what a network operating system is, you need to understand what just an OS is. So:

An operating system is a set of control and processing programs that, on the one hand, act as an interface between computer system devices and application programs, and on the other, are designed to control devices, manage computing processes, effectively distribute computing resources between computing processes and organize reliable computing . This definition applies to most modern general-purpose operating systems. In the logical structure of a typical computing system, the OS occupies a position between devices with their microarchitecture, machine language, and possibly native (embedded) firmware on the one hand, and application programs on the other. The OS allows software developers to abstract from the details of the implementation and operation of devices, providing the minimum required set of functions

In most computing systems, the OS is the main, most important (and sometimes the only) part of the system software. Since the 1990s, the most common operating systems have been the Microsoft Windows family of operating systems and UNIX-class systems (especially Linux).

A network operating system is an operating system with built-in capabilities for working in computer networks. Such opportunities include:

network equipment support
network protocol support
routing protocol support
network traffic filtering support
support for accessing remote resources such as printers, disks, etc. over the network
support for network authorization protocols
the presence in the system of network services that allow remote users to use computer resources

That is, SOS forms the basis of any computer network. Each computer on the network is largely autonomous, therefore, a network operating system in the broad sense is understood as a set of operating systems of individual computers that interact to exchange messages and share resources according to uniform rules - protocols. In a narrow sense, a network OS is the operating system of a separate computer that provides it with the ability to work on a network.

2) Network operating system

The network operating system of an individual machine can be divided into several parts:

Tools for managing local computer resources: functions for distributing RAM between processes, scheduling and dispatching processes, managing processors in multiprocessor machines, managing peripheral devices and other functions for managing local OS resources.
Means of providing own resources and services for general use - the server part of the OS (server). These tools provide, for example, file and record locking, which is necessary for their sharing; maintaining directories of names of network resources; processing requests for remote access to your own file system and database; managing queues of requests from remote users to their peripheral devices.
Means for requesting access to remote resources and services and their use - the client part of the OS (redirector). This part recognizes and forwards requests to remote resources from applications and users to the network, where the request comes from the application in a local form and is transmitted to the network in another form that meets the server's requirements. The client part also accepts responses from servers and converts them into a local format, so that the application is indistinguishable from executing local and remote requests.
Communication means of the OS, with the help of which messages are exchanged on the network. This part provides addressing and buffering of messages, selection of the route for transmitting messages over the network, reliability of transmission, etc., that is, it is a means of transporting messages.

Depending on the functions assigned to a particular computer, its operating system may lack either a client or server part.

The first network operating systems were a combination of an existing local operating system and a network shell built on top of it. At the same time, the minimum network functions necessary for the operation of the network shell, which performed the main network functions, were built into the local OS. An example of this approach is the use of the MS DOS operating system on each network machine (which, starting with its third version, has built-in functions such as file and record locking necessary for file sharing). The principle of building network operating systems in the form of a network shell over a local operating system is also used in modern operating systems, such as LANtastic or Personal Ware.

However, it seems more effective to develop operating systems that are initially designed to work on the network. Network functions of this type of OS are deeply built into the main modules of the system, which ensures their logical harmony, ease of operation and modification, as well as high performance. An example of such an OS is the Windows NT system from Microsoft, which, due to the built-in network tools, provides higher performance and information security compared to the LAN Manager network OS from the same company (joint development with IBM), which is an add-on over the local OS/2 operating system .

2.1 Peer-to-peer network OS and OS with dedicated servers

Depending on how the functions are distributed between computers on the network, network operating systems, and therefore networks, are divided into two classes: peer-to-peer and two-peer. The latter are more often called networks with dedicated servers.

If a computer provides its resources to other network users, then it plays the role of a server. In this case, a computer accessing the resources of another machine is a client. As already mentioned, a computer operating on a network can perform the functions of either a client or a server, or combine both of these functions.

If performing some server functions is the main purpose of the computer (for example, providing files for general use by all other network users or organizing fax sharing, or allowing all network users to run their applications on this computer), then such a computer is called a dedicated server. Depending on which server resource is shared, it is called a file server, fax server, print server, application server, etc.

Obviously, on dedicated servers it is advisable to install OSes that are specially optimized for performing certain server functions. Therefore, in networks with dedicated servers, network operating systems are most often used, which include several OS options that differ in the capabilities of the server parts. For example, the Novell NetWare network operating system has a server version optimized for operation as a file server, as well as shell options for workstations running various local operating systems, and these shells perform exclusively client functions. Another example of an OS aimed at building a network with a dedicated server is the Windows NT operating system. Unlike NetWare, both versions of this network OS - Windows NT Server (for a dedicated server) and Windows NT Workstation (for a workstation) - can support both client and server functions. But the server version of Windows NT has more opportunities for providing the resources of your computer to other network users, since it can perform a wider range of functions, supports a larger number of simultaneous connections with clients, implements centralized network management, and has more developed security features.

It is not customary to use a dedicated server as a computer to perform routine tasks not related to its main purpose, as this may reduce the performance of its work as a server. In connection with such considerations, the Novell NetWare OS does not provide the ability to run conventional application programs on the server side at all, that is, the server does not contain a client part, and there are no server components on workstations. However, in other network operating systems, functioning of the client part on a dedicated server is quite possible. For example, Windows NT Server can run regular local user programs that may require OS client functions to be executed when requests for resources from other computers on the network appear. In this case, workstations on which Windows NT Workstation is installed can perform the functions of a non-dedicated server.

It is important to understand that despite the fact that in a network with a dedicated server, all computers in the general case can simultaneously perform the roles of both server and client, this network is not functionally symmetrical: in hardware and software, two types of computers are implemented in it - one, to a greater extent focused on performing server functions and running specialized server OSes, while others primarily perform client functions and run the OS version appropriate for this purpose. Functional asymmetry, as a rule, also causes asymmetry in the equipment - for dedicated servers, more powerful computers with large amounts of RAM and external memory are used. Thus, functional asymmetry in networks with a dedicated server is accompanied by asymmetry of operating systems (OS specialization) and hardware asymmetry (computer specialization).

In peer-to-peer networks, all computers have equal access rights to each other's resources. Each user can, at his own discretion, declare any resource on his computer as shared, after which other users can exploit it. In such networks, all computers have the same OS installed, which provides all computers on the network with potentially equal capabilities. Peer-to-peer networks can be built, for example, on the basis of LANtastic, Personal Ware, Windows for Workgroup, Windows NT Workstation OS.

In peer-to-peer networks, functional asymmetry may also arise: some users do not want to share their resources with others, and in this case, their computers act as a client; the administrator has assigned only functions for organizing the sharing of resources to other computers, which means they are servers; In the case where a local user does not object to the use of his resources and does not exclude the possibility of accessing other computers, the OS installed on his computer must include both server and client parts. Unlike networks with dedicated servers, in peer-to-peer networks there is no OS specialization depending on the predominant functional focus - client or server. All variations are implemented by configuring the same OS version.

Peer-to-peer networks are easier to organize and operate, but they are used mainly to unite small groups of users who do not have great requirements for the volume of stored information, its security from unauthorized access and access speed. With increased requirements for these characteristics, two-rank networks are more suitable, where the server better solves the problem of serving users with its resources, since its equipment and network operating system are specially designed for this purpose.

2.2 OS for workgroups and OS for enterprise networks

Network operating systems have different properties depending on whether they are intended for workgroup (department)-scale networks, campus-scale networks, or enterprise-scale networks.

Departmental networks - used by a small group of employees solving common problems. The main purpose of a department network is to share local resources such as applications, data, laser printers, and modems. Departmental networks are not typically divided into subnets.
Campus networks - connect multiple networks of departments within a single building or within the same enterprise area. These networks are still local area networks, although they can cover an area of several square kilometers. Services of such a network include interaction between department networks, access to enterprise databases, access to fax servers, high-speed modems and high-speed printers.
Enterprise networks (corporate networks) - unite all computers of all territories of a separate enterprise. They can cover a city, a region, or even a continent. These networks provide users with access to information and applications located in other workgroups, departments, divisions, and corporate headquarters.

The main purpose of the operating system used in a department-wide network is to organize the sharing of resources such as applications, data, laser printers, and possibly low-speed modems. Typically departmental networks have one or two file servers and no more than 30 users. Management tasks at the department level are relatively simple. The administrator's tasks include adding new users, troubleshooting simple failures, installing new nodes, and installing new software versions. The operating systems of departmental networks are well-developed and varied, as are the departmental networks themselves, which have been in use for a long time and are quite well-functioning. Such a network usually uses one or at most two network operating systems. Most often this is a network with a dedicated NetWare 3.x or Windows NT server, or a peer-to-peer network such as a Windows for Workgroups network.

Users and administrators of departmental networks soon realize that they can improve their efficiency by gaining access to information from other departments in their enterprise. If a sales person can access specific product features and include them in a presentation, the information will be more current and have a greater impact on buyers. If the marketing department can access the characteristics of a product that is still being developed by the engineering department, then it can quickly prepare marketing materials immediately after development is completed.

So, the next step in the evolution of networks is to combine the local networks of several departments into a single network of a building or group of buildings. Such networks are called campus networks. Campus networks can extend over several kilometers, but do not require wide-area connections.

The operating system running on the campus network must provide employees in some departments with access to some files and resources on the networks of other departments. The services provided by campus network OSes go beyond simple file and printer sharing and often provide access to other types of servers, such as fax servers and high-speed modem servers. An important service provided by operating systems of this class is access to corporate databases, regardless of whether they are located on database servers or on minicomputers.

It is at the campus network level that integration problems begin. In general, departments have already chosen the types of computers, networking equipment, and network operating systems. For example, the engineering department may use the UNIX operating system and Ethernet network equipment, the sales department may use the DOS/Novell operating environment and Token Ring equipment. Very often, a campus network connects disparate computer systems, while departmental networks use similar computers.

The corporate network connects the networks of all departments of the enterprise, which are generally located at considerable distances. Corporate networks use WAN links to connect local networks or individual computers.

Enterprise network users require all of the applications and services found on departmental and campus networks, plus some additional applications and services, such as access to mainframe and minicomputer applications and global communications. When an OS is designed for a local network or workgroup, its main responsibility is to share files and other network resources (usually printers) among locally connected users. This approach is not applicable at the enterprise level. Along with the basic services associated with sharing files and printers, a network OS that is being developed for corporations must support a wider range of services, which usually includes mail service, collaboration tools, remote user support, fax service, voice message processing, organization of video conferences, etc.

In addition, many existing methods and approaches to solving traditional problems of smaller-scale networks for the enterprise network have proven unsuitable. Tasks and problems came to the fore that were either of secondary importance or did not appear at all in the networks of work groups, departments, and even campuses. For example, the simplest task of maintaining user records for a small network has grown into a complex problem for an enterprise-scale network. And the use of global communications requires enterprise operating systems to support protocols that work well on low-speed lines, and to abandon some traditionally used protocols (for example, those that actively use broadcast messages). The task of overcoming heterogeneity has acquired particular importance - numerous gateways have appeared on the network, ensuring the coordinated operation of various operating systems and network system applications.

2.3 Signs of corporate OS

The following features may also be included in the characteristics of corporate operating systems.

2.3.1 Application support

Enterprise networks run complex applications that require a lot of computing power to run. Such applications are divided into several parts, for example, on one computer the part of the application associated with executing queries to the database is executed, on the other - queries to the file service, and on client machines - the part that implements the application data processing logic and organizes the user interface. The computing part of the software systems shared by a corporation can be too voluminous and overwhelming for client workstations, so applications will run more efficiently if their most computationally complex parts are transferred to a powerful computer specially designed for this purpose - an application server.

The application server must be based on a powerful hardware platform (multiprocessor systems, often based on RISC processors, specialized cluster architectures). The application server OS must provide high computing performance, and therefore support multithreaded processing, preemptive multitasking, multiprocessing, virtual memory and the most popular application environments (UNIX, Windows, MS-DOS, OS/2). In this regard, the NetWare network operating system can hardly be classified as a corporate product, since it lacks almost all the requirements for an application server. At the same time, the good support for universal applications in Windows NT actually allows it to claim a place in the world of corporate products.

2.3.2 Help Desk

An enterprise OS must be able to store information about all users and resources in a way that can be managed from one central point. Like a large organization, a corporate network needs centralized storage of as complete background information as possible about itself (from data about users, servers, workstations to data about the cable system). It is natural to organize this information in the form of a database. Data from this database can be required by many network system applications, primarily management and administration systems. In addition, such a database is useful for organizing e-mail, group work systems, security services, network software and hardware inventory services, and for almost any large business application.

A database that stores reference information provides the same variety of capabilities and poses the same many problems as any other large database. It allows you to carry out various search operations, sorting, modification, etc., which makes life very much easier for both administrators and users. But these conveniences come at the price of solving the problems of distribution, replication and synchronization.

Ideally, network reference information should be implemented as a single database, and not be a set of databases specializing in storing information of one type or another, as is often the case in real operating systems. For example, Windows NT has at least five different types of help databases. The main domain directory (NT Domain Directory Service) stores information about users, which is used to organize their logical login to the network. Data about the same users may also be contained in another directory used by Microsoft Mail. Three more databases support low-level address resolution: WINS - matches Netbios names to IP addresses, the DNS directory - a domain name server - is useful when connecting an NT network to the Internet, and finally, the DHCP protocol directory is used to automatically assign IP addresses network computers. Closer to ideal are the directory services provided by Banyan (Streettalk III) and Novell (NetWare Directory Services), which offer a single directory for all network applications. The presence of a single help desk for a network operating system is one of the most important signs of its corporate character.

2.3.3 Security

Data security issues are of particular importance for the OS of a corporate network. On the one hand, in a large-scale network, there are objectively more opportunities for unauthorized access - due to the decentralization of data and the large distribution of “legitimate” access points, due to the large number of users whose trustworthiness is difficult to establish, and also due to the large number of possible points unauthorized connection to the network. On the other hand, enterprise business applications work with data that is vital to the success of the corporation as a whole. And to protect such data in corporate networks, along with various hardware, the entire range of protection tools provided by the operating system is used: selective or mandatory access rights, complex user authentication procedures, software encryption.

EXAMPLES OF SOS

Novell NetWare OS

Novell was one of the first companies to create LANs. It produced both hardware and software, but more recently Novell has focused its efforts on LAN software.

The following are some characteristics of NetWare software products: More applications can run on NetWare than on any other LAN. NetWare OS is capable of supporting workstations running DOS, DOS and Windows, OS/2, UNIX, Windows NT, Mac System 7 and other operating systems. A NetWare LAN can handle more different types of network adapters than any other operating system. You can choose hardware from many different vendors to achieve your goals. With NetWare you can use ARCnet, EtherNet, Token Ring, or virtually any other type of network adapter. A NetWare LAN can grow to enormous sizes. The NetWare LAN works reliably. The data protection provided by NetWare is more than sufficient for most LANs. NetWare allows the use of more than 200 types of network adapters, more than 100 types of disk storage subsystems, data duplication devices and file servers.

Novell has contracts to support NetWare OS with some of the largest and most powerful independent organizations, such as Bell Atlantic, DEC, Hewlett-Packard, Intel, Prime, Unisys and Xerox.

Network OS LAN Meneger, Windows NT and LAN Server

Although these network operating systems are less popular than OS NetWare, they are more suitable for the client/server software technology that is beginning to widely develop. Many experts believe that the future lies with this technology, so it is quite possible that in the future NetWare OS will lose its leading position, but for now it remains the most widespread and popular.

Both network operating systems LAN Manager and LAN Server operate based on OS/2. LAN Manager 2.2 requires OS/2 version 1.21 or later, while LAN Server 3.0 requires OS/2 2.0. Workstations can be controlled by DOS version 3.3 or OS/2 version 1.21.

Network OS LANtastic

In terms of popularity and number of sales, Artisoft's LANtastik network operating system has been the leader in the peer-to-peer LAN market for a long time. Therefore, Novell with Personal NetWare and Microsoft with Windows for Workgroups attempted to penetrate this market area created by Artisoft. All of these companies offer high-quality software, and therefore it is not without interest which of the software products will become the most popular on the market. The POWERLan network operating system is also a strong competitor and may in the future be able to displace network operating systems such as Windows for Workgroups, Personal NetWare and LANtastic.

LANtastic OS has a number of characteristics that allow it to function well, despite the fact that it is not the fastest networking OS for peer-to-peer LANs. LANtastic OS has excellent printer sharing capabilities. With additional hardware supplied by Artisoft, it is even possible to organize audio e-mail on a LAN. LANtastic OS requires very little memory and has facilities for partitioning CD-ROM drives. Artisoft offers Ethernet network adapters that work especially well with the LANtastic OS. It is possible to connect Macintosh computers to a LAN managed by LANtastic OS. This system is perfectly compatible with Windows. Technical support for the LANtastic OS includes an electronic bulletin board that can be accessed via modem, and telephone consultations from Artisoft in the user support department.

Bibliography

1. http://fmi.asf.ru/

http://fmi.asf.ru/library/book/Network/os_net.html

2. "Wikipedia" - version of the encyclopedia in Russian

http://ru.wikipedia.org

3. http://www.citforum.ru, Information Technology Server containing accessible information in Russian on all areas of computer technology.

Abstract on the course “COMPUTER NETWORKS”

NETWORK OPERATING SYSTEMS

Student group K7-05P

Nenarokova S.S.

General overview of network operating systems

A network operating system is required to manage the flow of communications between workstations and servers. It can allow any workstation to work with a shared network drive or printer that is not physically connected to that station.

Some computer networks have a dedicated stand-alone computer that functions only as a file server. Such systems are called LAN with a file server. In other, small LANs, the workstation can simultaneously perform the functions of a file server. These are peer-to-peer LANs.

The network operating system components on each workstation and file server communicate with each other through a language called a protocol. One common protocol is IBM's NetBIOS protocol. (Network Basic Input Output System - Network I/O operating system). Another common protocol is IPX (Internet-work Packet Exchange - Internetwork packet exchange) from Novell.

Below is a list of some network operating systems and their manufacturers:

operating system	Manufacturer
Apple Talk	Apple
LANtastic	Artisoft
NetWare	Novell
NetWare Lite	Novell
Personal NetWare	Novell
NFS	Sun Microsystems
OS/2 LAN Manager	Microsoft
OS/2 LAN Server	IBM
Windows NT Advanced Server	Microsoft
POWERfusion	Performance Technology
POWERLan	Performance Technology
Vines	Ba

OS NetWare companies Novell

Novell was one of the first companies to create LANs.

It produced both hardware and software, but more recently Novell has focused its efforts on LAN software.

More applications can run on NetWare than on any other LAN.

NetWare OS is capable of supporting workstations running DOS, DOS and Windows, OS/2, UNIX, Windows NT, Mac System 7 and other operating systems.

A NetWare LAN can handle more different types of network adapters than any other operating system. You can choose hardware from many different vendors to achieve your goals. With NetWare you can use ARCnet, EtherNet, Token Ring, or virtually any other type of network adapter.

A NetWare LAN can grow to enormous sizes.

The NetWare LAN works reliably.

The data protection provided by NetWare is more than sufficient for most LANs.

NetWare allows the use of more than 200 types of network adapters, more than 100 types of disk storage subsystems, data duplication devices and file servers.

Novell has support contracts for the NetWare operating system with some of the largest and most powerful independent organizations, such as Bell Atlantic, DEC, Hewlett-Packard, Intel, Prime, Unisys and Xerox.

Let's take a closer look at the structure of this OS.

A file server in NetWare is a regular PC, the network OS of which manages the operation of the LAN. Management functions include coordinating workstations and regulating the process of sharing files and printers on the LAN. Network files of all workstations are stored on the file server's hard drive, and not on disks workstations.

There are three versions of NetWare OS. Version 2.2 can run on an 80286 (or later) computer used as a file server. When purchasing an OS, you must purchase a license for the number of users (5, 10, 50, 100). NetWare OS versions 3.12 and newer 4.0 are designed for 32-bit bus architectures and 80386, 80486 or Pentium processors. There are also variants of the NetWare network operating system designed to run under multitasking, multi-user OS/2 and UNIX operating systems. NetWare OS version 3.12 can be purchased for 20, 100, or 250 users, and version 4.0 can support up to 1,000 users.

All OS versions are well compatible with each other, so on the same computer network you can have file servers with different versions of NetWare OS.

Some OS commands NetWare .

NPRINT- transferring a text file to the printer.

WHOAMI- user identification (information about the current session).

USERLIST- displaying the names of users connected to the LAN at the moment.

SEND- sending a message to any user.

NetWare distinguishes three types of drives: local drives, network drives, and search drives. Local drives are physically connected to workstations. Network storage devices are storage devices on file server hard drives. Just as DOS uses the PATH tool to specify a list of drives and directories in which application programs are searched by default, NetWare uses the concept of a search drive.

IDA- viewing the current status of drives (without parameters), and reassigning them (with parameters).

NetWare OS allows you to manipulate files and directories in various ways. You can copy, destroy, rename, write, print and share files on a LAN. There is also a certain system of access rights to files and directories.

Both files and directories on a server on a LAN running NetWare OS have attributes. These attributes can override the rights granted to users on the LAN.

RIGHTS- a list of rights that you have for this directory.

NCOPY- copying files.

NDIR- list of files in this directory. Unlike the DOS DIR command, it displays additional information for each file and directory.

CAPTURE- redirection of printing to a shared network printer.

Server and file system with OS NetWare

There are some differences between a NetWare LAN server and a regular PC. This computer's hard disk drive uses a completely different formatting structure than DOS. It is impossible to access the hard drive of such a server if you booted DOS from a floppy disk. But for a LAN user who is running DOS and has accessed the server from his terminal, the server’s hard drive appears simply as an additional one to the existing ones.

The hard disk recording format used in NetWare includes more information about files and directories than was possible in DOS. Files in NetWare OS, along with the “read-only”, “hidden” and “archive” attributes, can additionally have the “unshared” and “shared” attribute (this indicates the possibility of sharing the file on the LAN by many users at the same time). In addition, NetWare OS adds the following elements to the file information: the original creation date, the name of the file's creator, the date the file was last accessed, the date the file was last modified, and the date and time the file was last archived.

OS data protection NetWare

The NetWare LAN data protection system includes the following measures:

Protection against unauthorized access to the LAN by assigning names and passwords to users, as well as restrictions on access to the LAN by users with certain names at certain times of the day.

A system of trusted rights (trustee rights), which allows you to control which files and directories the user can access, as well as what operations he can perform with them.

A system of attributes for directories or files that determine the ability to copy, view, write and share them on a LAN.

For each directory there is maximum rights mask, which stores the maximum privileges that a user can have in it. The following are the eight rights that can be specified in this mask:

Read permission from open files

Write permission to open files

Right to open files

The right to create new files

Right to destroy files

The right to create, rename or delete subdirectories, and to establish trusted rights over directories within a directory and its subdirectories

The right to search files in a directory

The right to modify file attributes

System fault tolerance NetWare

Fault tolerance is one of the most important characteristics today, and NetWare developers paid due attention to this issue. NetWare OS versions 2.2, 3.12 and 4.0 use SFT technology (System Fault Tolerant - C equipment failure protection system). C equipment failure protection system -vania means uninterrupted operation of the file server in the event of various types of hardware failures. All versions of NetWare include features to minimize data loss in the event of physical damage to the drive surface. The SFT system went further in this regard by proposing methods disk mirroring And disk duplication

The NetWare system has the ability to monitor signals from the UPS uninterruptible power supply. When a power outage is detected, the OS notifies users and tells them how much time they have to complete their work. After this period of time, the OS will automatically close all files on the system and shut down itself.

Finally, the SFT system offers a TTS (request tracing) system. Application programs that use this system interpret a sequence of database actions as a single operation - either all actions were completed successfully, or none of them

Comparative characteristics of different versions

Network operating system structure

The network operating system forms the basis of any computer network. Each computer on the network is largely autonomous, therefore, a network operating system in the broad sense is understood as a set of operating systems of individual computers that interact to exchange messages and share resources according to uniform rules - protocols. In a narrow sense, a network OS is the operating system of a separate computer that provides it with the ability to work on a network.

Rice. 4.1.

In the network operating system of an individual machine, several parts can be distinguished (Figure 4.1):

Tools for managing local computer resources: functions for distributing RAM between processes, scheduling and dispatching processes, managing processors in multiprocessor machines, managing peripheral devices and other functions for managing local OS resources.

Means of providing own resources and services for general use - the server part of the OS (server). These tools provide, for example, file and record locking, which is necessary for their sharing; maintaining directories of names of network resources; processing requests for remote access to your own file system and database; managing queues of requests from remote users to their peripheral devices. Means for requesting access to remote resources and services and their use - the client part of the OS (redirector). This part recognizes and forwards requests to remote resources from applications and users to the network, where the request comes from the application in a local form and is transmitted to the network in another form that meets the server's requirements. The client side also accepts responses from servers and converts them into a local format, so that the application makes no difference between local and remote requests. Communication means of the OS, with the help of which messages are exchanged on the network. This part provides addressing and buffering of messages, selection of the route for transmitting messages over the network, reliability of transmission, etc., that is, it is a means of transporting messages.

Depending on the functions assigned to a particular computer, its operating system may lack either a client or server part.

Figure 4.2 shows the interaction of network components. Here computer 1 plays the role of a “pure” client, and computer 2 plays the role of a “pure” server, respectively, the first machine does not have a server part, and the second one does not have a client part. The figure separately shows the client side component - the redirector. It is the redirector that intercepts all requests coming from applications and analyzes them. If a request is issued to a resource on a given computer, it is forwarded to the appropriate subsystem of the local OS, but if it is a request to a remote resource, then it is forwarded to the network. In this case, the client part converts the request from a local form into a network format and transmits it to the transport subsystem, which is responsible for delivering messages to the specified server. The server part of the operating system of computer 2 receives the request, transforms it and passes it on to its local OS for execution. After the result is received, the server contacts the transport subsystem and sends a response to the client that issued the request. The client part converts the result into the appropriate format and addresses it to the application that issued the request.

Rice. 4.2.

In practice, several approaches to building network operating systems have emerged (Figure 4.3).

Rice. 4.3.

Peer-to-peer network OS and OS with dedicated servers

Depending on how the functions are distributed between computers on the network, network operating systems, and therefore networks, are divided into two classes: peer-to-peer and two-toe (Figure 4.4). The latter are more often called networks with dedicated servers.

Rice. 4.4. (a) - Peer-to-peer network,

(b) - Two-rank network

In peer-to-peer networks, all computers are equal in access rights to each other's resources. Each user can, at his own discretion, declare any resource of his computer as shared, after which other users can exploit it. In such networks, all computers have the same OS installed, which provides all computers on the network with potentially equal capabilities. Peer-to-peer networks can be built, for example, on the basis of LANtastic, Personal Ware, Windows for Workgroup, Windows NT Workstation OS.

OS for workgroups and OS for enterprise networks

Network operating systems have different properties depending on whether they are intended for workgroup (department)-scale networks, campus-scale networks, or enterprise-scale networks.

Departmental networks - used by a small group of employees solving common problems. The main purpose of a department network is to share local resources such as applications, data, laser printers, and modems. Departmental networks are not typically divided into subnets. Campus networks - connect multiple networks of departments within a single building or within the same enterprise area. These networks are still local area networks, although they can cover an area of several square kilometers. Services of such a network include interaction between department networks, access to enterprise databases, access to fax servers, high-speed modems and high-speed printers. Enterprise networks (corporate networks) - unite all computers of all territories of a separate enterprise. They can cover a city, a region, or even a continent. These networks provide users with access to information and applications located in other workgroups, departments, divisions, and corporate headquarters.

The next step in the evolution of networks is the consolidation of local networks of several departments into a single network of a building or group of buildings. Such networks are called campus networks. Campus networks can extend over several kilometers, but do not require wide-area connections.

Enterprise network users require all of the applications and services found on departmental and campus networks, plus some additional applications and services, such as access to minicomputer applications and global communications. When an OS is designed for a local network or workgroup, its main responsibility is to share files and other network resources (usually printers) among locally connected users. This approach is not applicable at the enterprise level. Along with the basic services associated with sharing files and printers, a network OS that is being developed for corporations must support a wider range of services, which usually includes mail service, collaboration tools, remote user support, fax service, voice message processing, organization of video conferences, etc.

Application support. Enterprise networks run complex applications that require a lot of computing power to run. Such applications are divided into several parts, for example, on one computer the part of the application associated with executing queries to the database is executed, on the other - queries to the file service, and on client machines - the part that implements the application data processing logic and organizes the user interface. The computing part of the software systems shared by a corporation can be too voluminous and overwhelming for client workstations, so applications will run more efficiently if their most computationally complex parts are transferred to a powerful computer specially designed for this purpose - an application server. The application server must be based on a powerful hardware platform, multiprocessor systems, often based on RISC processors, specialized cluster architectures. The application server OS must provide high computing performance, and therefore support multithreaded processing, preemptive multitasking, multiprocessing, virtual memory and the most popular application environments (UNIX, Windows, MS-DOS, OS/2). In this regard, the NetWare network operating system can hardly be classified as a corporate product, since it lacks almost all the requirements for an application server. At the same time, the good support for universal applications in Windows NT actually allows it to claim a place in the world of corporate products.

Help Desk. An enterprise OS must be able to store information about all users and resources in a way that can be managed from one central point. Like a large organization, a corporate network needs centralized storage of as complete background information as possible about itself (from data about users, servers, workstations to data about the cable system). It is natural to organize this information in the form of a database. Data from this database can be required by many network system applications, primarily management and administration systems. In addition, such a database is useful for organizing e-mail, group work systems, security services, network software and hardware inventory services, and for almost any large business application. Ideally, network reference information should be implemented as a single database, and not be a set of databases specializing in storing information of one type or another, as is often the case in real operating systems. For example, Windows NT has at least five different types of help databases. The main domain directory (NT Domain Directory Service) stores information about users, which is used to organize their logical login to the network. Data about the same users may also be contained in another directory used by Microsoft Mail. Three more databases support low-level address resolution: WINS - matches Netbios names to IP addresses, the DNS directory - a domain name server - is useful when connecting an NT network to the Internet, and finally, the DHCP protocol directory is used to automatically assign IP addresses network computers. Closer to ideal are the directory services provided by Banyan (Streettalk III) and Novell (NetWare Directory Services), which offer a single directory for all network applications. The presence of a single help desk for a network operating system is one of the most important signs of its corporate character.

Safety . Data security issues are of particular importance for the OS of a corporate network. On the one hand, in a large-scale network, there are objectively more opportunities for unauthorized access - due to the decentralization of data and the large distribution of “legitimate” access points, due to the large number of users whose trustworthiness is difficult to establish, and also due to the large number of possible points unauthorized connection to the network. On the other hand, enterprise business applications work with data that is vital to the success of the corporation as a whole. And to protect such data in corporate networks, along with various hardware, the entire range of protection tools provided by the operating system is used: selective or mandatory access rights, complex user authentication procedures, software encryption.

Network operating system is an operating system with built-in capabilities for working in computer networks. These capabilities include: support for network equipment; support for network protocols; support for routing protocols; support for filtering network traffic; support for access to remote resources such as printers, disks, etc. over the network; support for network authorization protocols; the presence in the system of network services that allow remote users to use computer resources.

Examples of network operating systems: Novell NetWare; Microsoft Windows (95, NT and later); Various UNIX systems such as Solaris, FreeBSD; Various GNU/Linux systems; IOS; ZyNOS by ZyXEL.

Main purpose. The main tasks are the division of network resources (for example, disk space) and network administration. Using network functions, the system administrator defines shared resources, sets passwords, and determines access rights for each user or group of users. Hence the division:

— network OS for servers;

— network OS for users.

There are special network operating systems that have the functions of conventional systems (Ex: Windows NT) and regular operating systems (Ex: Windows XP) that have network functions. Today, almost all modern operating systems have built-in network functions.

Network operating system structure

In a network operating system A separate machine can be divided into several parts (Figure 1.1):

The means of providing your own resources and services for public use is the server part of the OS (server). These tools provide, for example, file and record locking, which is necessary for their sharing; maintaining directories of names of network resources; processing requests for remote access to your own file system and database; managing queues of requests from remote users to their peripheral devices.

Means for requesting access to remote resources and services and their use - the client part of the OS (redirector). This part recognizes and forwards requests to remote resources from applications and users to the network, where the request comes from the application in a local form and is transmitted to the network in another form that meets the server's requirements. The client part also accepts responses from servers and converts them into a local format, so that the application is indistinguishable from executing local and remote requests.

Communication means of the OS, with the help of which messages are exchanged on the network. This part provides addressing and buffering of messages, selection of the route for transmitting messages over the network, reliability of transmission, etc., that is, it is a means of transporting messages.

Depending on the functions assigned to a particular computer, its operating system may lack either a client or server part.