Network subsystems

For what kind of the system users will decide depending on its activities and the system design is closely related to the functioning of the organization in which it is introduced and the design of software that will be used on a computer system. Depending on their needs will depend on the way of realization of the network and its bulkiness. Components of a LAN (Local Area Network) that one should choose from are:

The correct way to take care of these components Network Operating System (NOS). Operating system independent computer has only the task of managing its resources. NOS has a similar role, manages resources in a much greater range and intercepts own OS computers to local resources that are designed for shared use. Modern operating systems, whether they are designed for the purpose server (Windows Server, Linux server ...) and as an operating system workstation (PC) users, have incorporated the NOS. Operating Systems PC Users (OS X, Windows XP, Windows 7, Ubuntu Linux ...) have server features, but for the purpose of servicing the less demanding tasks, such as the availability (share) of the printer for a group of participants.

Network operating system includes the following subsystems:

Program support server basically acts independently, possibly a small part of another operating system (DOS or Windows 95, for example) is used to initiate the computer and NOS switch on the server. Most of the action network is managed from the server to which the larger and more important part of the NOS. A smaller part of the NOS on work stations, which allows them to be members of the network and possibly a portion of their resources available to the network. NOS workstation depends on the operating system of the computer that was on your station (WOS - Workstation operating system) and must be coordinated with, rather complements it.

When the computer network architecture type Peer-to-Peer (P2P) NOS in the same structure with the same capabilities present on each computer. Such a computing system based on the example on Windows or Linux platforms, each computer is on a network has both server and user preferences. This type of network allows communication between the users themselves. At the present time the NOS as an independent term is redundant. Almost every personal computer has network capabilities that are to a greater or lesser extent aligned with the OSI (Open System Interconnection) recommendations; way of connecting computers and network systems in accordance with standards of the International Organization for Standardization (ISO) for the exchange of information. Who does not care recommendations can be networked with those who hold, or become an equal participant in the network. Simple mechanism unity without coercion :-).

Modern operating systems are computer users as Windows XP, Windows 7, OS X or Ubuntu have incorporated NOS that is almost universally accepted based on the TCP / IP network communications solutions, and which listed computer operating systems supported by the network can operate independently without a server. But the role of the server in the network the user is not negligible because of the services provided to clients, as well as the exchange of e-mails, for example whether the internal level, or the level of information exchange between networks, storing data in a database, and more. Since the servers are based on the amount of service they provide powerful hardware device, their operating systems must in this regard support multiple users, and safety precautions when accessing their resources need to be stricter. Security services server is not on him only purpose, but will serve in this regard and computer users operating system patch installation on users' computers or addition of antivirus signatures and related specific tasks.

Applicability of the network, especially today with the cheaper network resources, not at all questionable, from treasury coffers and offices in the shop, bookkeeping services, commercial banks, to the complex network of state as electric power and PTT. In everyday practice commonly encountered types of client-server networks.

According to the mode of action, a service provided by the server can be:

Which of the functions performed by the server how many will be determined by user needs and requirements for stability, security and speed of the system. In this sense, all the services that the server can provide the above, will take place on a single computer or on a server with several interconnected computer servers distributed tasks, depending on the amount of traffic and services that must be enabled and capabilities of individual servers and the accordingly the number of servers depends which will be applied to their individual purposes.

All that we have said in describing the basic PHYSICAL connectivity of the participants in the network, which usually coincides with LOGICAL network functionality. Logical function describes how data is exchanged within the network. Largely based on the same principles as in the concentrated and distributed architectures. Today the most commonly used business purpose client-server architecture, and in the same physical structure can be multiple servers, but each destined for a different group of users, and basically the server do not communicate. Within the physical unit operates more logical entity that may or may not be intertwined. Such logical structure will have some of his principles connectivity as it has a physical structure. So, every structure has its rules connectivity - TOPOLOGY, the physical or logical arrangement of participants (nodes) in the network.

Network devices are an important factor in network communications, regardless of whether the local network users - LAN (Local Area Network) or the network connection to each other. Depending on the type of network is different selection of network devices that will use the network. Network equipment manufacturers with a wide range of devices allow interconnection few hundred computers or computer or an institution linking the institutions themselves or, more comprehensively, taking into account all aspects of the security and management of network traffic. In general, the task of network devices is to connect all network nodes about their mutual communication.

The nodes communicate and exchange data by some kind of defined rules (protocols) and as already noted in most cases business purpose of data exchange is a client-server concepts. On one or more servers are connected to all the relevant data for the group of users and all users request data from the server, or give him orders, but among themselves almost never communicate. Communication by e-mail also belongs to this group because it is done through the server dedicated for this purpose. Disadvantage of this concept is that the server must 'suffer' big push users. In most cases allows the users to use the same information in a manner that a user process and return to the servers or server processing its orders, and are then available to other users. Mutual communication between the user does not have. But it can become a big problem if the exchange huge amounts of data without processing. The server must allow access to each user, which is a heavy burden and its computing resources must be powerful in order to meet the requirements and throughput capacity of the network to them must be very large.

This concept is not good for the mutual exchange of information between users and the established rules (protocols) that allow communication to large groups of users share such a large file, but piece by piece so that each participant takes the piece that is missing from someone else and not always the same users who have this piece, to the receipt of all the pieces compiled file. This is the logical way of communicating peer users (nodes) in the physical network; peer-to-peer networking, one-to-one (P2P). This way of communicating and corresponding protocols used his program support as Shareaza, eDonkey, Gnutella, BitTorrent and similar server and serves only as an address book users to know where it is or what the user made available to the network. The server does not care about communication between users. Of course, this is particularly popular in the exchange of authorized content (video, music ...), which is not according to the letter of the law.

It has already been identified in the codes that have been introduced and standardized so people can understand each other. The same applies to the method of communication that must be standardized, which defines rules called protocols. The basis of today's communication network systems, the TCP / IP suite of protocols that can be added to others for achieving particular goals as BitTorrent - violently rapid flow of bits. The protocols in a later Chapter.