Today's article opens a new section on the blog, which will be called " networks". This section will cover a wide range of issues related to computer networks . The first articles of the rubric will be devoted to explaining some of the basic concepts that you will encounter when working with the network. And today we will talk about what components will be required to create a network and which ones exist. types of networks.

Computer network is a set of computer and network equipment connected via communication channels in single system. To create a computer network, we need the following components:

• computers that have networking capabilities (for example, a network card that is in every modern PC);
• transmission medium or communication channels (cable, satellite, telephone, fiber-optic and radio channels);
• network equipment (for example, a switch or router);
• network software (usually included with operating system or supplied with the network equipment).

Computer networks are usually divided into two main types: global and local.

Local networks(Local Area Network - LAN) have a closed infrastructure before reaching Internet service providers. The term "local area network" can describe both a small office network and the network of a large factory covering several hectares. In relation to organizations, enterprises, firms, the term is used corporate network – local network of a separate organization ( legal entity) regardless of the territory it occupies.
Corporate networks are networks of a closed type, access to them is allowed only to a limited circle of users (for example, company employees). Global networks are focused on serving any users.

Global network(Wide Area Network - WAN) spans large geographic regions and consists of many local area networks. Everyone is familiar with the global network, which consists of several thousand networks and computers - this is the Internet.

The system administrator has to deal with local (corporate) networks. A typical user computer connected to a local network is called workstation . A computer that shares its resources with other computers on a network is called server ; and the computer accessing the shared resources on the server is client .

There are various types of servers: file (for storing shared files), database servers, application servers (providing remote work programs on clients), web servers (for storing web content) and others.

Network load is characterized by a parameter called traffic. Traffic is the flow of messages in a data network. Under it is understood quantitative measurement the number of data blocks passing through the network and their length, expressed in bits per second. For example, the data transfer rate in modern local networks can be 100Mbps or 1Gbps

At present, the world has great amount all kinds of network and computer equipment that allows you to organize a variety of computer networks. The whole variety of computer networks can be divided into several types according to various criteria:

By territory:

• local - cover small areas and are located inside individual offices, banks, corporations, houses;
• regional - are formed by combining local networks in separate territories;
• global (Internet).

By way of connecting computers:

• wired (computers are connected via cable);
• wireless (computers exchange information via radio waves. For example, by WI-FI technologies or bluetooth).

Control method:

• with centralized management - one or more machines (servers) are allocated to manage the process of data exchange in the network;
• decentralized networks - do not contain dedicated servers, network management functions are transferred in turn from one computer to another.

According to the composition of computing facilities:

• homogeneous - combine homogeneous computing tools (computers);
• heterogeneous - combine various computing tools (for example: PCs, trading terminals, webcams and network storage).

By type of transmission medium networks are divided into fiber-optic, with the transmission of information via radio channels, in the infrared range, through satellite channel etc.

You may come across other classifications of computer networks. Usually, system administrator one has to deal with local wired networks with centralized or decentralized control.

Depending on the method of managing shared resources, a computer network can be organized in the following ways:

· how peer-to-peer working group, in which each computer performs the function of both a server and a client, and each user independently manages the resources of his computer;

as a network client/server, in which network administration functions are concentrated on a central computer.

Let's take a closer look at these networks. Let us first give the main definitions of terms.

Server- a computer that provides its resources (data, software, peripheral equipment, etc.) to the network.

Client– a computer accessing network resources.

Often the server provides (shares) only a special kind of resource, so it is called dedicated. As a rule, a dedicated server is a computer with a fast processor and a large amount of memory. In large networks, dedicated servers perform only one specific function, for example, they can be one of the following types:

file server - a server that stores data files and performs all operations for their maintenance;

print server - a computer that manages one or more printers distributed on a network;

application server - a computer with network applications installed on it (intended for execution on client machines);

· registration server - designed to ensure the security of databases. AT Windows networks it is called a domain controller, it contains information about user accounts;

· web server– performs software for supporting Internet protocols and technologies;

server Email– performs e-mail service;

server remote access- provides a dial-up connection (with its help, the computer accesses the network through a telephone line);

telephone server - serves telephone network;

Cluster server - provides a combination of servers in clusters, that is, into groups of independent computer systems working together as one system;

Proxy server - performs the functions of an intermediate link between users' computers and the Internet;

Fax server - receives, sends and distributes incoming faxes;

BOOTP server - using the BOOTP protocol, loads the OS of client machines that do not have hard drives, and provides information about configuring the network protocol;

· DHCP server – assigns IP addresses and TCP/IP protocol configuration parameters to client computers.

Term client can also refer to programs that have access to server programs.

Term work station can mean any desktop computer with a client OS, or a high performance computer running network-intensive applications.

Term host stands for any network device, which is assigned an IP address.

Term node indicates a connection point in a network.

In general, this is a device programmed or designed to recognize and process requests to transmit information to other nodes.

Peer-to-peer network is well suited for small networks, its cost is low. Such a network is configured as a workgroup in which all computers have equal rights and can act as both clients and servers. The user of each computer is responsible for the administration of his machine. Access to the resources of such a network is carried out using passwords. A peer-to-peer network is said to have resource-level security (that is, each resource is assigned a specific password that must be known in order to gain access). It is clear that as the size of the network increases, such a security system makes the network inoperable.

The disadvantages of a peer-to-peer network are devoid of a client / server network with centralized control implemented on one of the network machines (server). As a rule, the server in such networks provides several networking opportunities listed above. The administrative problem that arises (with an increase in the number of computers) in a peer-to-peer network is solved much more simply and efficiently in a client / server network. However, this raises the need for a specially trained network administrator. In addition, the server must certainly have very high performance in order to be able to handle all network requests.

Access to client / server network resources is carried out at the user level, that is, there is a special user base in which the rights of each user are registered, and access to resources is carried out in accordance with these assigned rights.

Network management tools.

Any complex computer network requires additional special controls beyond those found in standard network operating systems. This is due to a large number of various communication equipment, the operation of which is critical for the network to perform its basic functions. The distributed nature of a major corporate network makes it impossible to maintain its work without a centralized control system, which in automatic mode collects information about the status of each hub, switch, multiplexer and router and provides this information to the network operator. Usually, the control system operates in an automated mode, performing the simplest actions to manage the network automatically, and allowing complex decisions to be made by a person based on the information prepared by the system. The control system must be integrated. This means that the functions of managing heterogeneous devices should serve the common goal of serving the end users of the network with a given quality.

The control systems themselves are complex software and hardware systems, so there is a limit to the expediency of using the control system - it depends on the complexity of the network, the variety of communication equipment used and the degree of its distribution over the territory. In a small network, you can use separate programs to manage the most complex devices, such as a switch that supports VLAN technology. Typically, each device that requires a fairly complex configuration, the manufacturer accompanies standalone program configuration and management. However, as the network grows, the problem of integrating disparate device management programs into a single management system may arise, and to solve this problem, you may have to abandon these programs and replace them with an integrated management system.

The architecture of a computer network management system is understood as a set of objects and links that combine tools that provide comprehensive administrative management of computing systems, and tools for managing ongoing processes in accordance with the requirements for the efficiency of using network capabilities to provide information and computing services to users.

Conventionally, the entire network in terms of control can be divided into a control system and a control object. The control system includes a set of computing tools designed to generate control actions and analyze information, on the basis of which a decision is made about control. Most network management architectures use the same basic structure and set of relationships.

The basic network management architecture consists of the following main elements:

network management system;

objects of control;

· information base management;

network control protocol.

In this case, as a rule, the network management system includes such elements as a set of control applications that help analyze data and troubleshoot, as well as an interface with which the network administrator can manage the network.

Typically, the system management system performs the following functions:

Accounting for used hardware and software tools (Configuration Management). The system automatically collects information about computers installed on the network and creates entries in a special database of hardware and software resources. An administrator can then quickly find out what resources he has and where a particular resource is located, for example, which computers need to update printer drivers, which computers have enough memory, disk space etc.

Distribution and installation software (Configuration Management). After the survey is completed, the administrator can create distribution packages for new software to be installed on all computers on the network or on a group of computers. In a large network where the benefits of a control system are shown, this installation method can significantly reduce the complexity of this procedure. The system may also allow you to centrally install and administer applications that run with file servers, as well as enable end users to run such applications from any workstation networks.

Remote performance and problem analysis(Fault Management and Performance Management). This group of functions allows you to remotely measure the most important parameters computer, operating system, DBMS, etc. (for example, CPU utilization, page fault rate, physical memory utilization, transaction rate). To resolve problems, this group of functions can give the administrator the ability to take over remote control computer in emulation mode GUI popular operating systems. The management system database usually stores detailed information about the configuration of all computers on the network in order to be able to perform remote analysis emerging problems.

Network configuration and naming management

· error processing;

· performance and reliability analysis;

security management;

Accounting for the network.

challenging task is to configure switches and routers to support routes and virtual paths between network users. Agreed manual setting routing tables with a complete or partial rejection of the use of a routing protocol (and in some global networks, such as X.25, such a protocol simply does not exist) is a difficult task.

Switching is rightfully considered one of the most popular modern technologies. Switches on all fronts are crowding bridges and routers, leaving behind the latter only the organization of communication through the global network. The popularity of switches is primarily due to the fact that they allow you to increase network performance through segmentation. In addition to dividing the network into small segments, switches make it possible to create logical networks and easily regroup devices in them. In other words, switches allow you to create virtual networks.

Switch- a device designed as a network hub and acting as a high-speed multi-port bridge; the built-in switching mechanism allows you to segment the local network, as well as allocate bandwidth to end stations in the network.

There are three methods of switching in local networks:

Switching "on the fly" (cut-through);

Fragment-free switching;

Switching with buffering (store-and-forward switching).

At switching on the fly the incoming data packet is transmitted to the output port immediately after reading the destination address. The analysis of the entire package is not carried out. And this means that packets with errors can be skipped. This method provides the most high speed switching. Frames are transmitted in the following sequence:

1. Reception of the first bytes of the frame (including the destination address byte);

2. Search for the destination address in the address table;

3. Construction of a switching path by a matrix;

4. Reception of the remaining bytes of the frame;

5. Forwarding all bytes of the frame to the output port through the switching matrix;

6. Gaining access to the transmission medium;

7. Frame transmission to the network.

In this case, the switch can check the transmitted frames, but cannot remove bad frames from the network, since some of the bytes have already been sent to the network. Using on-the-fly switching provides significant performance gains, but at the expense of reliability. In networks with collision detection technology, the transmission of malformed frames can lead to a violation of data integrity.

At buffered switching the input packet is received completely, then it is checked for errors (the check is performed by the checksum) and only if no errors were found, the packet is transmitted to the output port. This method guarantees complete filtering of erroneous packets, however, at the cost of reducing the throughput of the switch compared to on-the-fly switching.

Fragmentless switching occupies an intermediate position between these two methods: it buffers only the first 64 bytes of the packet. If the packet ends there, the switch checks for checksum errors. If the packet is longer, it is sent to the output port without checking.

On different ports of the switch, errors can occur with different intensity. In this regard, it is very useful to be able to choose the switching method. This technology is called adaptive switching. Adaptive switching technology allows you to set for each port the mode of operation that is optimal for it. At first, switching on ports is carried out “on the fly”, then those ports on which many errors occur are switched to fragmentless switching mode. If, after this, the number of unfiltered packets with errors remains large (which is quite likely if many packets longer than 64 bytes are transmitted over the network), the port is switched to buffered switching mode.

In networks with information routing, the problem of data routing arises. In circuit-switched systems and when creating a virtual circuit, routing is organized once when the initial connection is established. At normal modes In packet and message switching, routing occurs continuously as data travels from one switching node to another. There are two main routing methods: pre-connected, in which before the start of data exchange between network nodes, a connection with certain parameters must be established, and dynamic, which uses datagram-type protocols that transmit a message to the network without first establishing a connection.

Routing consists in the correct choice of the output channel in the switching node based on the address contained in the header of the packet (message).

Routing can be centralized and decentralized. Centralized Routing allowed only in networks with centralized control: route selection is carried out in the network control center and switches in the nodes only implement the received decision. At decentralized routing control functions are distributed between switching nodes, which, as a rule, have a connecting processor.

A local area network (LAN) is a collection of computers and other computing equipment (active network equipment, printers, scanners, etc.) connected via cables and network adapters and running a network operating system.

According to network topology.

Network topology is the geometric shape of a network. Depending on the topology of node connections, there are bus (backbone), ring, star and mixed topology networks.

Bus (bus) - a local network in which communication between any two stations is established through one common path, and the data transmitted by any station is simultaneously available to all other stations connected to the same data transmission medium.

Ring (ring) - nodes are connected by a ring data transmission line (only two lines go to each node); data, passing through the ring, in turn become available to all network nodes;

Star (star) - there is a central node, from which data lines diverge to each of the other nodes;

Mixed (mixed) is a type of network topology that contains some features of the main network topologies (bus, star, ring).

a) Tire b) Ring c) Star

Figure 2 - Types of topologies

Distance between nodes.

Depending on the distances between connected nodes, computer networks are distinguished:

Regional (Metropolitan Area Network, MAN) - use global network technology to connect local networks in a specific geographic region, such as a city. Regional networks denote.

Wide Area Networks (WANs) are networks that can connect networks around the world, such as networks from multiple cities, regions, or countries.

Local (Local Area Network, LAN, LAN) - are a set of networked computers located within a small physical region, such as one or more buildings.

By way of management.

Depending on the control method, networks are distinguished:

Client/server - one or more nodes are allocated in them (their name is servers) that perform control or special service functions on the network, and the remaining nodes (clients) are terminal, users work in them.

Peer-to-peer - in them all nodes are equal; Since, in general, a client is an object (device or program) that requests some services, and a server is an object that provides these services, each node in peer-to-peer networks can perform the functions of both a client and a server.

By access method.

There are random and deterministic access methods.

Among the random methods, the best known is the carrier sense multiple access method with collision detection. The English name of the method is Carrier Sense Multiple Access /Collision Detection (CSMA/CD).

Among deterministic methods, marker access methods predominate. The token method is a method of accessing the data transmission medium in a LAN, based on the transfer of authority to the transmitting station using a special information object called a token.

A computer network is a number of computers within a limited area (located in the same room, in one or more closely spaced buildings) and connected to unified lines connections. Today, most computer networks are local area networks (Local-Area Networks), which are located within a single office building and are based on computer model client/server. network connection consists of two computers participating in communication and a path between them. You can create a network using wireless technology, but this is not widespread yet.

In the client/server model, network communication is divided into two areas: the client side and the server side. By definition, a client requests information or services from a server. The server, in turn, serves the client's requests. Often, each side in a client/server model can act as both a server and a client. When creating a computer network, there are various components to choose from that determine what software and hardware you can use to form your corporate network. A computer network is an integral part of today's business infrastructure, and a corporate network is just one of the applications used in it and, accordingly, should not be the only factor determining the choice of network components. The components necessary for the Intranet should be an addition to the existing network without leading to a significant change in its architectures.

Network management method

Each organization formulates its own network configuration requirements, determined by the nature of the tasks to be solved. First of all, it is necessary to determine how many people will work in the network. From this decision, in essence, all subsequent stages of creating a network will depend.

The number of workstations directly depends on the expected number of employees. Another factor is the hierarchy of the company. For a company with a horizontal structure, where all employees must have access to each other's data, a simple peer-to-peer network is the optimal solution.

A company built on the principle of a vertical structure, in which it is known exactly which employee and what information should have access, should focus on the more expensive version of the network - with a dedicated server. Only in such a network is it possible to administer access rights.

Network type selection.

In this case, the enterprise has 30 workstations, which need to be combined into a corporate network. Moreover, they are grouped into the following groups:

§ director of the enterprise - 1 workstation;

§ Department of direct subordination - 2 workstations;

§ secretary - 1 workstation;

§ departments 1, 2 and 3 of the 2nd department with 3, 3 and 4 workstations, respectively;

§ departments 4 and 5 of the 3rd department, 4 and 4 workstations each;

§ department 6 of the 4th department - 4 workstations.

Following from the network type selection scheme, we can decide that in this case a server installation is required, since we have a vertical structure of the enterprise, that is, differentiated access to information.

One of the main stages of planning is the creation of a preliminary scheme. In this case, depending on the type of network, the question arises of limiting the length of the cable segment. This may not be significant for a small office, but if the network spans several floors of a building, the problem appears in a completely different light. In this case, it is necessary to install additional repeaters (repeater).

In an enterprise situation, the entire network will be located on the same floor, and the distance between network segments is not so great that the use of repeaters is required.

Server hosting

Unlike setting up a peer-to-peer network, when building a LAN with a server, another question arises - where is the best place to install a server.

Several factors influence the choice of location:

§ due to high level it is advisable to install the server separately from other workstations;

§ it is necessary to provide constant access to the server for maintenance;

§ for reasons of information security, it is required to restrict access to the server;

The server is located in the network administrator's room, since only this room meets the requirements, that is, the noise level in the room is minimal, the room is isolated from others, therefore, access to the server will be limited.

The network administrator will be able to constantly monitor the operation of the server and perform server maintenance, since when the server was installed.

Network architecture

Network architecture is the combination of topology, access method, and standards required to create a workable network.

The choice of topology is determined, in particular, by the layout of the room in which the LAN is deployed. Besides, great importance have the cost of acquiring and installing network equipment, which is an important issue for the company, the price range here is also quite large.

The star topology is a more productive structure, each computer, including the server, is connected by a separate cable segment to a central hub (HAB).

The main advantage of such a network is its resistance to failures that occur due to malfunctions on individual PCs or due to damage to the network cable.

The most important characteristic of the exchange of information in local networks are the so-called access methods (access methods), which regulate the order in which the workstation gets access to network resources and can exchange data.

The abbreviation CSMA / CD hides the English expression "Carrier Sense Multiple Access with Collision Detection" (multiple access with carrier sense and collision detection). With this method, all computers get equal access to the network. Each workstation checks whether the channel is free before starting data transmission. At the end of the transmission, each workstation checks whether the sent data packet has reached the destination. If the answer is negative, the node repeats the data transmission/reception control cycle and so on until it receives a message about the successful reception of information by the addressee.

Since this method has proven itself well in small and medium-sized networks, for an enterprise this method fit. In addition, the Ethernet network architecture that the enterprise network will use uses this particular access method.

The Ethernet specification was proposed by the Xerox Corporation in the late seventies. Later, Digital Equipment Corporation (DEC) and Intel Corporation joined this project. In 1982, the specification for Ethernet version 2.0 was published. Based on Ethernet, the IEEE 802.3 standard was developed by the IEEE.

Twisted-pair (10Base-T) cable technology is currently the most popular. Such a cable does not cause difficulties when laying.

A twisted-pair network, unlike thin and thick coax, is built on a star topology. To build a network in a star topology, more cable is required (but the cost of twisted pair is not high). Such a scheme also has an invaluable advantage - high fault tolerance. The failure of one or more workstations does not lead to the failure of the entire system. True, if the hub fails, its failure will affect all devices connected through it.

Another advantage this option is the ease of network expansion, since when using additional hubs (up to four in series), it becomes possible to connect a large number of workstations (up to 1024). When using unshielded twisted pair (UTP), the length of the segment between the hub and the workstation should not exceed 100 meters, which is not observed in the enterprise.

Network resources

The next important aspect of network planning is sharing network resources (printers, faxes, modems).

The listed resources can be used both in peer-to-peer networks and in networks with a dedicated server. However, in the case of a peer-to-peer network, its shortcomings are immediately revealed. To work with the listed components, they must be installed on a workstation or connected to it peripherals. When this station is disabled, all components and related services become unavailable for shared use.

In networks with a server, such a computer exists by definition. network server never shuts down except for short maintenance stops. Thus, round-the-clock access of workstations to network periphery is provided.

The enterprise has ten printers: in each separate room. The administration went to the expense to create the most comfortable working conditions for the team.

Now the question of connecting the printer to the LAN. There are several ways to do this.

1.Connection to a workstation.

The printer is connected to the workstation that is closest to it, as a result of which this workstation becomes the print server. The disadvantage of this connection is that when printing jobs are performed, the performance of the workstation decreases for a while, which will negatively affect the work of application programs when the printer is used intensively. Also, if the machine is turned off, the print server will become inaccessible to other hosts.

2.Direct connection to the server.

The printer is connected to the server's parallel port using a special cable. In this case, it is permanently available to all workstations. The disadvantage of this solution is due to the limitation in the length of the printer cable, which ensures correct data transfer. Although the cable can be run for 10 meters or more, it must be run in conduits or floors, which will increase networking costs.

3. Connect to the network through a special network interface.

The printer is equipped with a network interface and connects to the network as a workstation. The interface card acts as a network adapter, and the printer is registered to the server as a LAN node. The server software sends print jobs over the network directly to a connected network printer.

In networks with a bus topology, a network printer, like workstations, is connected to network cable using a T-connector, and when using a "star" - through a hub.

An interface card can be installed in most printers, but its cost is quite high.

4. Connect to a dedicated print server.

An alternative to the third option is to use dedicated print servers. Such a server is a network interface arranged in a separate housing with one or more connectors (ports) for connecting printers. However, in this case, using a print server is impractical.

In our case, due to the unprofitability of installing a special network printer, by purchasing a separate interface card for the printer, the most suitable way to connect a network printer is to connect to a workstation. This decision was also influenced by the fact that printers are located near those workstations that need the greatest printer.

Ethernet Configuration Calculation Methodology

In order for an Ethernet network consisting of segments of different physical nature to work correctly, three basic conditions must be met:

The number of stations in the network does not exceed 1024 (subject to limitations for coaxial segments).

Double the propagation delay (Path Delay Value, PDV) between the two most remote friend from each other by network stations does not exceed 575 bit intervals.

Reducing the interframe distance (Interpacket Gap Shrinkage) when passing a sequence of frames through all repeaters by no more than 49 bit intervals (recall that when sending frames, the station provides an initial interframe distance of 96 bit intervals).

Compliance with these requirements ensures the correct operation of the network even in cases where violations simple rules configurations that define maximum amount repeaters and the maximum segment length of each type.

The physical meaning of limiting the signal propagation delay over the network has already been explained - compliance with this requirement ensures timely detection of collisions.

The requirement for a minimum interframe distance is due to the fact that when a frame passes through a repeater, this distance decreases. Each packet received by the repeater is resynchronized to eliminate signal jitter accumulated during the passage of the pulse train through the cable and through the interface circuits. The resynchronization process typically increases the length of the preamble, which reduces the inter-frame interval. When passing frames through several repeaters, the interframe interval may decrease so much that network adapters in the last segment, there will not be enough time to process the previous frame, as a result of which the frame will simply be lost. Therefore, the total reduction of the interframe interval by more than 49 bit intervals is not allowed. The amount of decrease in the interframe distance during the transition between adjacent segments is usually called in the English literature Segment Variable Value (SVV), and the total amount of decrease in the interframe interval when passing all repeaters is Path Variable Value (PVV). Obviously, the value of PVV is equal to the sum of SVV of all segments except the last one.

Network Management Standards and Tools

Any more or less complex computer network requires additional special management tools in addition to those that are available in standard network operating systems. This is due to the fact that a new class of equipment appears in large networks - intelligent hubs and routers that create an active transport system. Such equipment is characterized by a large number of parameters that require configuration, settings and control by the administrator. And although special control and monitoring tools are built into communication equipment to facilitate this task, the distribution of these devices requires a centralized system that, receiving data from the built-in tools about the status of each device, organizes a consistent and stable work networks in general.

* Network configuration and naming management - consists of configuring network components, including parameters such as their location, network addresses and identifiers, managing parameters of network operating systems, maintaining a network diagram, and these functions are used to name objects.

Error handling is the identification, definition and elimination of the consequences of failures and failures in the network.

Performance analysis - helps to evaluate the system response time and schedule value based on the accumulated statistical information, as well as plan the development of the network.

Security management - includes access control and maintaining data integrity. These functions include the authentication procedure, privilege checks, support for encryption keys, authority management. This group also includes important mechanisms for managing passwords, external access, and connections to other networks.

Network accounting - includes registration and management of used resources and devices. This function operates on concepts such as usage time and resource charges.

Network management tools are often confused with computer management tools and their operating systems. The former are often referred to as Network Management tools and the latter as System Management tools.

System controls typically perform the following functions:

Accounting for the hardware and software used. The system automatically collects information about scanned computers and creates entries in the database of hardware and software resources. After that, the administrator can quickly find out what he has and where it is located. For example, find out which computers need to update printer drivers, which PCs have enough memory and disk space, and so on.

Distribution and installation of software. Once the survey is complete, the administrator can create software distribution packages - very effective method to reduce the cost of such a procedure. The system may also allow centralized installation and administration of applications that run from file servers, as well as enable end users to run such applications from any network workstation.

Remote performance and problem analysis. The administrator can remotely control the mouse, keyboard and see the screen of any PC running on the network running a particular network operating system. The management system database typically stores detailed information about the configuration of all computers on the network so that problems can be analyzed remotely.

As you can see from the above lists, network management tools and system management tools often perform similar functions, but in relation to different objects. In the first case, the object of control is communication equipment, and in the second case, software and Hardware network computers. However, some functions of these two types of control systems may be duplicated (for example, system controls may perform simple network analysis).

Examples of system management tools are products such as System management server Microsoft or Intel's LAN Desk Manager, while HP Open View, SunNet Manager, and IBM NetView are typical network management tools. Naturally, in this course devoted to the study of communication equipment, only network management systems are considered.

Determining system requirements

After an inventory of an existing computing system, it is necessary to determine the requirements for new system. For determining technical parameters networks consider system requirements not from a technical point of view, but from the positions of leaders, managers and end users.

To find out the system requirements, you need to answer the following questions:

What needs to be connected? Do employees in any department need to communicate with a small (large) number of people within a small area, or do they need to communicate with a small (large) number of people within a geographically large area? The volume and distribution of the schedule will help determine the required computer power, as well as the types and speeds of communication equipment and services.

What existing hardware and software will be used in the new system? What systems should be left in the developed corporate network? Do these systems need to be networked? Will existing systems work fine in new network? Are there any enterprise standards, are there prevailing applications? What equipment and applications do you need to add to meet your production goals?

How much information will be transferred over the network? The amount of transmitted information determines the required throughput networks. Will more or less information be transmitted over the corporate network? Determine this by counting the number of network users, the average number of transactions per day per user, and the average transaction volume. Such a calculation will help determine the media access technology (Ethernet, FDDI,...) and global service requirements.

What network response time is acceptable? Will users wait one second, half a second, or two seconds? Such measurements will help determine the speed requirements of hardware, applications, and communication links.

How long is the network essential for the operation of the enterprise? Do you need network 24 hours a day and 7 days a week, or only for 8 hours a day and 5 days a week? Should I increase my current network usage settings?

What are the requirements for mean time to troubleshoot? How do network maintenance and repair operations affect the efficiency of the business? Will the business lose $5 million or $100,000 if the network goes down for one hour? What will be the damage from network downtime for two hours?

What is the planned growth of the system? What is the current network utilization rate and how can it change over the next 6 months, one year, two years? Even if you carefully planned the network, but did not take into account the possibilities of its growth and development, then the system requirements will have to be changed and increased. Network growth must be planned in advance, and not just react to the actual growth of its load.

Let's look at the two main ways to build a wireless network in Windows system XP Professional.

peer-to-peer network

The simplest wireless network consists of two computers equipped with wireless network cards. As you can see in Figure 5.14, there is no need for an access point, and whenever these two computers are within range of each other, they form their own independent network. Such a network is called a peer-to-peer network. These responsive networks are particularly easy to install and configure. They don't need administration and presetting configuration. In this case, each computer gets access only to the resources of another computer, and not to a central server or the Internet. Networks of this type are ideal for home, small business or one-time needs.

Internal networks

As in conventional computer networks, indoor (inside the building) wireless network equipment consists of a PC card, PCI and ISA client adapters, and access points.

Like a typical small local area network, a WLAN can be made up of a pair of computers exchanging information, or it can use a topology that changes along the way, in which only network cards clients. To expand a wireless LAN or to increase its functionality, access points are used, which can act as a bridge to an Ethernet network.

Applying WLAN technology to desktop systems gives an organization flexibility that is simply not possible with traditional LANs. Client devices can be placed where the cable cannot be laid. Moreover, clients can be rearranged at any time as needed. All this makes wireless networks Ideal for temporary workgroups or fast growing organizations.