Computers and other components of a local network can be connected to each other in various ways. The physical layout of network components used is called Topology. The topology of a network is determined by the geometric figure formed by the communication lines between computers, or the physical location in relation to each other of computers connected to each other. Network topology can serve as one of the characteristics for comparing and classifying different computer networks.
There are three main topologies for building a local network:
– star (Star);
– ring (Ring);
– bus (Bus).
In a network with a star topology, all computers are connected to a central computer, or (hub). All data arrives at the central node, which transmits it directly to the recipient. In this topology, there are no direct connections between computers on the network. All information is transmitted only through the hub (central computer). A special device can be used as a hub - a concentrator, which is a multiport repeater (repeater). The main function of the repeater is to receive data on one of the ports and immediately redirect it to other ports.
Organization of a network with a star topology is simple and effective. If one of the cables connecting an individual network computer to the hub breaks, the connection between the remaining computers connected according to this scheme will remain operational. If the central computer itself is disabled, then data transfer between computers on such a network will be impossible.
Advantages of star topology:
– disruption of the connection in one place, except for the central node, does not interrupt the operation of the local network;
– when connecting a large number of computers, there is no decrease in performance;
– information security is ensured at a high level, since computers do not receive other people’s data.
Disadvantages of star topology:
– high consumption of connecting cable;
– failure of the central node leads to the inoperability of the entire network;
– network expansion is associated with large financial costs.
In a ring topology there are no end connection points, i.e. the network turns out to be closed in an unbreakable ring.
In a network built on a ring topology, data is transferred in one direction from one computer in the ring to another. The computer does not transmit information until it receives a special token.
Advantages of ring topology:
– when connecting a large number of computers, there is only a slight decrease in performance.
Disadvantages of ring topology:
– a connection failure in one place leads to the cessation of the entire local network;
– information security is not ensured at a very high level: data sent from one computer on the network to another can be easily intercepted by any computer on the network for which it is not intended, which can violate the confidentiality of the transmitted information.
The “bus” topology uses one common communication channel (most often based on a coaxial cable) to transmit data, to which all computers on the local network are connected.
Working in a network with a “bus” topology is carried out as follows. When one of the computers on a local network with a bus topology sends data, it is transmitted along the cable in both directions and is received by all computers without exception, but only the one to whom it was intended uses it. Data in a network with a bus topology can flow in any direction at the same time. Special plugs - terminators - are installed at opposite ends of the bus.
Advantages of the bus topology:
– ease of network expansion;
– not very high cost of equipment.
Disadvantages of bus topology:
– a connection failure in one place leads to the inoperability of the entire local network;
– when a large number of computers are connected to one bus, a sharp decrease in performance occurs;
– information security is not ensured at a high level
Having considered local network topologies, I chose a star topology. Because of the advantages of this topology. Let's consider this topology in more detail. Star is the most common topology in Russia and Europe. The star has a central unit - a hub or switch. The concept of a star network topology comes from the field of mainframe computers, in which the head machine receives and processes all data from peripheral devices as the active processing node. This principle is used in data communication systems, such as the RelCom e-mail network. All information between two peripheral workstations passes through the central node of the computer network.
LAN topology structure in the form of a “star”
Network throughput is determined by the computing power of the node and is guaranteed for each workstation. Cabling is quite simple as each workstation is connected to a node. Cabling costs are high, especially when the central node is not geographically located in the center of the topology.
When expanding computer networks, previously made cable connections cannot be used: a separate cable must be laid from the center of the network to the new workplace.
The star topology is the fastest of all computer network topologies because data transfer between workstations passes through a central node (if its performance is good) over separate lines used only by these workstations. The frequency of requests to transfer information from one station to another is low compared to that achieved in other topologies.
The central control node - the server - implements the optimal protection mechanism against unauthorized access to information. The entire computer network can be controlled from its center. But there is also a drawback: if the central component fails, the entire network will stop. And if only one computer (or the cable connecting it to the hub (switch)) fails, then only this computer will not be able to transmit or receive data over the network. This failure will not affect other computers on the network.
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Introduction
Now the age of computerization has arrived. Even the smallest companies have computers.
Naturally, for full-fledged work an exchange of information is required. This is why local networks are designed.
What does a local network allow:
1. Exchange of information between network members. (Documents, completed student work, programs, etc.)
The speed of a modern network allows you to completely freely watch movies and listen to music from a remote computer, without even copying them to your hard drive, let alone transferring documents. But in the process of work, large programs can be used. Therefore, if this is suddenly required, then 1 gigabyte of data can be rewritten in just ten minutes.
2. The ability to share equipment such as printers, CD-RW/DVD/DVD-RW.
3. Sharing of the Internet access channel.
There are a lot of options here, the fact is that when the Internet access channel is wide enough, we are talking about a leased line or ADSL, then even with simultaneous access by a large number of users there will not be a noticeable drop in speed.
4. Multiplatform
Using a LAN, you can connect computers of any type (For example: PC and Macintosh) and with any operating systems. (Windows, Unix, OS/2, MacOs).
1.Selection of topology and network structure
1.1 Network structure
The structure of a network depends entirely on the physical and logical location of computers on the network.
We have: 3 separate classrooms with computers (logically the lower level, since these are students);
1 group of teachers’ computers, one in each classroom and 4 in a separate office (middle level).
2 servers: Internet server and file server (they are part of the teachers’ group - for ease of administration).
(See the structure diagram in Appendix No. 1)
1.2 Selecting a network topology.
There are several types of topologies:
Bus (mono channel)
Bus topology, implemented by a cable laid from one computer to another in the form of a daisy chain, reminiscent of a garland on a Christmas tree. All signals transmitted by any computer to the network travel along the bus in both directions to all other computers. The two ends of the bus must be “closed” using electrical resistances that nullify the voltages coming to these ends so that the signals do not reflect or go in the opposite direction. The main disadvantage of the bus topology is that, like a Christmas tree garland, a cable defect anywhere along its length divides the network into two parts that are unable to communicate with each other. Most networks built on coaxial cables, such as Ethernet networks, use a bus architecture.
· Ring
The ring topology is functionally equivalent to a bus whose ends are connected to each other; Thus, signals are transmitted from one computer to another, moving in a circle. However, a communication ring is only a logical abstraction and not a physical construct. In effect, the network is a star, but a special hub implements a logical ring by forwarding the incoming signal only through the next downstream port (instead of passing through all ports, as the hub does in a star topology). Each computer, upon receiving an incoming signal, processes it (if necessary) and sends it back to the hub for transmission to the next workstation on the network. In accordance with this operating principle, the system transmitting the signal to the network must also remove it after it has bypassed the entire ring completely. Networks constructed using a ring topology can use a variety of cable types. For example, Token Ring networks use twisted pair cables, while FDDI networks implement a ring topology using fiber optic cables.
Tree-like
This is a subtype of mixed tire, consisting of two tires.
Star-shaped
A star topology uses a separate cable for each computer, running from a central device called a hub or hub. The hub broadcasts signals arriving at any of its ports to all other ports; As a result, signals sent by one node reach other computers. A star-based network is more resilient to damage than a bus-based network, since cable damage directly affects only the computer to which it is connected, and not the entire network. Most networks using twisted pair cable are installed in a star topology, such as 10 BaseT Ethernet.
· Mixed
These are several different or identical topologies interconnected.
Now we need to decide what topology our network will have. Considering that we have several classes, a teacher network, and an Internet connection, our network topology will be mixed - a tree star.
The use of this particular topology was chosen because we need to connect several different segments into one “global” network.
The use of routing is unjustified. DNS - servers, domains, gateways, etc. will not be used. This will simplify our network and improve its performance a little:
When using a gateway or domain, a problem may arise - if it breaks down, the entire segment becomes inoperable.
(See the topology diagram in Appendix No. 2.)
2. Selection of network components
2.1 Network cables
There are 3 main types of network conductors with a lot of variations; the type of network cards and switch that we will use in our network depends on the choice of network cable (appearance in Appendix No. 3).
2.1.1 Twisted Pair
Currently, the most common network conductor in structure resembles a multi-core telephone cable, and has 8 copper cores intertwined with each other and good dense polyvinyl chloride insulation. Provides high connection speeds up to 100 megabits. There are Unshielded and Shielded twisted pair cables. Sold by most computer companies.
Twisted pair cable is less susceptible to electromagnetic interference, especially shielded cable. Even when laying unshielded twisted pair cable near an electrical distribution panel, and together with high voltage lines, relatively stable network operation was observed at speeds of over 80 megabits per second. The cable is extremely easy to repair (despite the fact that, according to standards, the damaged section cannot be repaired) and is extended using electrical tape and scissors. Even with numerous sections of breaks restored in this way, the twisted-pair network operates stably, although the communication speed drops somewhat.
2.1.1a 1000 megabit network (Gigabit Lan)
In addition, in networks based on twisted pair, various non-standard conductors can be used to obtain new characteristics and properties of the network.
1000 megabit networks are a further stage in the evolution of twisted pair networks. Unlike 10/100 megabit networks, which use only 4 of the 8 wires, a gigabit connection uses all 8 wires, using the appropriate network card hardware and a gigabit-capable switch. The data transfer rate is about 80-100 megabytes per second, which, as a rule, significantly exceeds the data transfer flows of hard drives (40-60 megabytes/sec). Despite the fact that such a connection is 10 times faster than a regular 100 megabit connection, using a gigabit network is somewhat difficult due to the high cost of gigabit switches and network cards.
Also, when using a gigabit network, it is necessary that the twisted pair be laid strictly according to standards without strong kinks, and it is also unacceptable to use twisted soldering to build up such a network.
2.1.2 Coaxial Cable
One of the first conductors used for laying networks. It contains a central conductor, a layer of braided insulator and plastic insulation, sometimes there are more layers of insulation, sometimes less. The maximum data transfer speed is 10 megabits. It is quite susceptible to electromagnetic interference. If damaged, it is difficult to repair, requiring soldering and careful insulation, but even then the repaired section is slow and unstable. In the area of the damaged area, reflections of electromagnetic waves propagating in the coaxial cable appear, which leads to distortion of the transmitted signal. The only advantage of coaxial cable over twisted pair is the greater distance of about 600-700 meters over which data can be transmitted. However, the use of twisted pair and alternative conductors, for example P-296 field cable, allows you to achieve stable communication at a speed of 10 megabits at a distance of up to 500 meters.
Currently, coaxial cable is mainly used as a signal conductor for satellite dishes and other antennas. In computer networks, the use of coaxial cable is usually not justified.
2.1.3 Optic Fiber cable
One or more light guides, well protected with plastic insulation. Ultra-high data transfer speed, the cable is absolutely free from interference. The distance between systems connected by optical fiber can exceed 2 kilometers. However, the cable is extremely expensive and working with it requires special network equipment (Network cards, Hubs, etc.), which is also not cheap. Optical fiber cannot be repaired; if damaged, the section must be re-laid.
It is perhaps obvious that twisted pair cable is optimal in terms of all characteristics and cost for use in our network.
Its cost is 9 rubles. per meter
(For the method of installation, see Appendix No. 4)
2.2 Network Switch
Hub - (Hub) when a network card sends a data packet, the Hub simply divides and amplifies the signal so that all network users receive it, but only the network card to which the data packet is addressed receives it. Obviously, when several users work simultaneously, the network speed drops sharply. Currently, most companies have simply stopped producing hubs and switched to producing more efficient Switches.
Switch - (Switch), unlike Hub, analyzes where and where a packet of information is sent and connects only these computers, while the remaining channels remain free. Of course, it is better to use Switch, as it works much faster especially on networks with many users. Externally, Switch is practically no different from Hub.
(Appendix No. 3)
2.2.1.1 Which Switch should I choose?
There are many models and types of network switches available these days, and their prices and features vary greatly.
2.2.1.2 Operation speed
The switch can operate at a speed of 10 or 100 megabits; the speed of the entire network depends on this.
10 Mbit switches now cost about $15-$20, but don't try to save money by using a cheaper 10 Mbit switch. A speed of 10 megabits is quite enough for small texts, but it is not quite suitable for the active exchange of significant (several gigabytes) volumes of information, especially on a large local network. In addition, you need to take into account that in fact 10 megabits (about 1.2 megabytes per second) is the maximum Theoretical speed; in reality, data will be transferred at a speed of about 6-8 megabits, and even less on long sections of the network.
Therefore, the need to use 100 megabit equipment is obvious.
2.2.1.3 Number of ports
This defining indicator characterizes the number of computers that can be connected to such a hub. This parameter also largely determines the price of the Switch.
Our choice fell on switches with 16 ports: 15 computers + 1 “teacher-router”.
2.2.1.4 Print Server support
A very useful, but not always necessary function, which, however, is not present on all switches. This is the presence on the switch of an additional, usually LPT or less often USB connector; if you connect a printer to this connector, it will become available to all members of the LAN. In this case, the printer does not depend on any computer on the network.
We do not need this function, since printers are available on teacher computers.
2.2.1.5 Support for additional network conductors
Some so-called hybrid switches have additional BNC connectors (for coaxial cable or fiber optic). In view of the above difficulties, when using coaxial and fiber optic, it is not worth purchasing hybrid switches. In addition, their price is much higher than usual.
Ethernet switch SwitchHub 16port 10/100MBps
High-quality and cheap ones support a connection of 100 megabits, they are quite compact, do not require any configuration and cost between $35-45, they are optimal for building a LAN.
2.2.3 Connecting 2 switches
Most modern switches/hubs have a special Uplink connector (It is often combined with the first port of the hub) you can simply plug a regular standard crimped network cable into it and that’s it.
If the Uplink port is already busy or does not exist. Then you will need a twisted pair crossover. A crossover cable can connect 2 or more switches using any identical ports.
3. Selecting computer components
It’s probably worth mentioning right away that my opinion is that the computers of students and teachers should be the same. I think this will put a little emphasis on some kind of equality between teacher and student. In addition, it is easier to choose an average computer configuration that meets the requirements of both.
This chapter details teacher and student workstations.
3.1 Do you need “video” and “sound”?
Probably every third person has a computer. Over the past 10 years there have been huge leaps in component performance.
Nowadays, many new programs are appearing that place great demands on computers. But there is one BUT - these are mainly either games or serious programs that work with 2D and 3D graphics (video, photo and cartoon 2D and 3D editors).
The network being developed will not deal with such issues. Of course, students study PhotoShop and Compass, but their requirements are not so great.
So, we conclude:
We don't need powerful sound and video cards;
You can save on this by purchasing a motherboard with built-in “sound” and “video”.
3.2 Motherboard
Based on the above and taking into account possible further modernization, I decided to take the EPOX 5EGA+ motherboard as a basis.
Specifications:
Chipset:
Northbridge: 915G
South Bridge: ICH6R
· Processor: Pentium 4, Celeron, Hyper Threading support.
· Memory: dual-channel DDR 400/333/266 - 4 slots, up to 4GB.
· Expansion slots: 4x PCI, 2x PCI Express 1x, PCI Express 16x
· Disk subsystem: UDMA ATA 100/66, 2x UDMA ATA133, 4x Serial ATA, support RAID0, RAID1, RAID0+1
· Integrated solutions:
· Video card: Intel GMA900
· Network adapter: Marvell 88e8001 1GB.
· Connectors: 2x Com, LPT, VGA, MIDI, PS/2 keyboard, PS/2 mouse, S/P DIF (input/output), RJ45, 8x USB 2.0/1.1, audio - line input, multi-channel outputs and microphone
Form factor: ATX
· Price: $137
I decided to go with this board because, in my opinion, it has an average price/quality ratio.
This board supports PCI slots, which is very useful now (and there are 4 of them!). And it supports PCI Express 1x slots, which will be useful in the future with possible upgrades.
This “mother” has a pretty good video card built into it, the Intel GMA 900. This is one of the latest chips. Plus, if this video fails, you can always install PCI Express 16x video (which is useful - since AGP cards will begin to “disappear” in the future). It is worth noting that the built-in card supports DX9.0.
The package contents of this board are quite complete: instructions (including in Russian), a disk with drivers, cables, 2 Molex-SATA power adapters, 2 SATA cables, a PCI bracket with small COM and MIDI ports. In addition, the box contains a screwdriver (2 Phillips and 2 regular bits), a set of radiators for power capacitors and a thermocouple for measuring the temperature of the component you are interested in inside the computer - software on disk.
This board has only two obvious drawbacks:
1) slightly overpriced;
2) unusual location of the memory - it is located close to the edge, this can make it difficult to change/install, since it may end up under the CD-ROM.
3.3 Processor
Based on considerations of material savings and the fact that these computers will not perform tasks requiring large resources, I decided to go with the Intel Celeron D processor.
Specifications:
· Core: Prescott. Bit size - 3 bits.
· Connector: LGA775, Socket 478.
· Frequency characteristics: clock frequency - 2.26 - 2.93 GHz. System bus frequency is 533 MHz.
· Thermoelectric characteristics: maximum core temperature - 67 degrees, power dissipation - 73 - 84 W, core voltage - 1.3 - 1.4 V.
· Caches: first level cache - 16 KB of data, 12,000 microinstructions. Second level cache - 256 KB. Bus L1-L2 with a capacity of 256 bits.
· Computational pipelines: a 31-stage pipeline. Three pipelined ALU units, two pipelined FPU units, two address calculation units.
· Additional command sets: SSE, SSE2, SSE3, MMX.
· Features: support for Execute Disable Bit technology (LGA775 platform only)
· Price: $90
This processor can be called a “cut-down Pentium”. Since, firstly, it has a very significant, 4-fold reduction in the size of the second level cache (instead of 1024Mb - 256Mb). Secondly, the system bus frequency is not 800, but only 533 MHz. Finally, the core of these processors does not support Hyper-Threading technology, which significantly speeds up the execution of multi-threaded applications.
The bottleneck in the form of a reduced cache and a reduced system bus frequency significantly limits the performance of Intel Celeron D models. On the other hand, due to the high frequency they are able to achieve good performance results.
Thus, we get a cheap entry-level processor.
When using our motherboard there is always an upgrade option.
3.4 Hard drive
In my opinion, 80GB is enough for student workstations, and 120GB for teachers.
Accordingly, I selected good and relatively cheap SATA HDDs.
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Characteristics |
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Formatted capacity, GB |
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Spindle rotation speed, rpm |
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Cache memory volume, MB |
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Total search time, ms |
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Idle noise, dB |
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Search noise |
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Operating temperature, °C |
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Number of plates |
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Number of heads |
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Peculiarities |
Minimal noise in standby mode. There is no ringing and almost no vibration. Low heating. |
In tests it showed average performance results. In search mode, the heads do not produce significant noise. There is little noise in standby mode. There is no ringing, vibration is insignificant. Moderate heating. |
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3.5 RAM, drive, FDD, power supply, keyboard and mouse
These parts of the system unit do not need a detailed description.
RAM - random access memory.
Comparing DDR and DDR2 does not make sense, since we are limited by the capabilities of the motherboard.
Naturally, it makes no sense to put less than 512MB on our system, but it’s also pointless to put more than that. The manufacturing company will depend only on the price (for us this is the main factor).
Price approximately 60$
The drive is a CD reader.
Nowadays, DVD technologies are often used, and the cost of inexpensive CD and DVD drives differs by about $5-10.
Conclusion - we buy DVD-ROM (about $40) for “students” and DVD-RW and DVD-ROM (together about $120) for “teachers”.
FDD - floppy disk reader.
It would seem unnecessary, but often a saving part of the computer.
Cost around $10
The power supply is what supplies electricity to the entire system unit.
The housings are also sold together with the power supply (included), but we are not interested in the appearance.
Computers are quite demanding when it comes to electricity, so less than 350W is not suitable for us.
Cost about $25-35.
The keyboard and mouse are integral parts of the computer.
We are not interested in appearance and “additional functions”; our choice is the cheapest and most reliable (wireless ones are not suitable for us).
All together $10-15.
3.6 Monitor
Here we have to make a choice: price - quality. Those. Which monitor to buy: LCD or CRT?
LCD is a new technology. It is safer for the eyes and requires less electricity consumption. But it's expensive for us. Some of the cheapest LCD monitors (17 inches) cost around 8,500 rubles.
CRT is cheaper. In addition, they have clearer graphics (although we don’t need this, but still a plus). Cost: teacher's workplace - $250, student's workplace - $150.
Thus, we get the total cost of computers:
Computer at the teacher’s workplace - $811
Computer at the student’s workplace - $608
3.7 Internet server and file server
A detailed description of the hardware of these machines (in my opinion) is not required, since performance is important here.
Internet server is a computer that controls access to the Internet.
It is required to distribute and limit access to the Internet, monitor traffic “leaks,” and provide additional protection against viruses and hackers from the Internet.
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Mat. Pay |
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CPU |
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RAM |
2x DDR 512Mb Kingston |
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Maxtor 40Gb UATA |
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Power supply (case) |
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LG 15" Studioworks 505E |
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Keyboard + mouse |
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A file server is a computer designed to store information.
The file server performs the following functions: data storage, data archiving, data transfer, authorized access to data, control over saving and changing files.
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Mat. Pay |
Gigabyte GA-8i915P-G/i915P/s775 |
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CPU |
Intel Pentium4 -3200E/1Mb 800FSB BOX |
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RAM |
2x DDR 512Mb Kingston |
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Seagate 300GB SATA |
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Power supply (case) |
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LG 15" Studioworks 505E |
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Keyboard + mouse |
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4. Network settings
To connect computers we will use the TCP/IP protocol. This is necessary for the use of some programs and better addressing when transmitting information.
4.1 Types of IP addresses
The settings within the audiences will be almost the same - the only difference will be in the IP address of the segment and the name of the group.
First of all, what is an IP address:
Anatomy of IP addresses
Before we dive into subnetting, we need to understand the basics of IP addresses.
IP addresses characterize network connections, NOT computers!
First of all, let's find out the main reason for the misunderstanding - IP addresses are not assigned to computers. IP addresses are assigned to network interfaces on computers.
What's behind this?
Currently, many (if not most) computers on an IP network have a single network interface (and, as a result, have a single IP address). Computers (and other devices) may have several (if not many) network interfaces - and each interface will have its own IP address.
So, a device with 6 working interfaces (for example, a router) will have 6 IP addresses - one for each network to which it is connected.
Despite this, most people refer to machine addresses when referring to IP addresses. Just remember that this is a simplified form for the IP address of a specific device on that computer. Many (if not most) devices on the Internet have only one interface and thus a single IP address.
IP addresses as "quadruple numbers separated by dots"
In the current (IPv4) implementation of IP addresses, an IP address consists of 4 (8-bit) bytes - it represents 32 bits of available information. This results in numbers that are quite large (even when written in decimal notation). Therefore, for convenience (and for organizational reasons), IP addresses are usually written as four numbers separated by dots. IP address
An example of this is 4 (decimal) numbers separated by (.) periods.
Because each of these numbers is a decimal representation of a byte (8 bits), each can range from 0 to 255 (256 unique values in total, including zero).
In addition, part of the computer’s IP address determines the network in which the computer is located; the remaining “bits” of the IP address determine the computer itself (network interface)
IP addresses are divided into 5 classes. These classes are determined by the subnet mask.
The subnet mask divides the 32 bits of the address into 2 parts. One part is the network address definition bits (ones). The other part is the network interface address definition bits (zeros).
Here is a list of masks of the first three classes of networks (bit decomposition in parentheses):
· Class A - 255.0.0.0
(1111 1111.0000 0000.0000 0000.0000 0000)
· Class B - 255.255.0.0
(1111 1111.1111 1111.0000 0000.0000 0000)
· Class C - 255.255.255.0
(1111 1111.1111 1111.1111 1111.0000 0000)
From these masks it can be seen that class A may have few segments, but many computer addresses in each segment. In class C, on the contrary, there are many segments, few addresses.
Only certain IP addresses can be used in each class:
Class A: 0.0.0.0 - 127.0.0.0
Class B: 128.0.0.0 - 191.255.0.0
Class C: 192.0.0.0 - 223.255.255.0
In addition to these classes, there is a division into subnetworks - when one of the zero bits is replaced with ones (for example, 1111 1111.1100 0000.0000 0000.0000 0000). This is how we get several from one subnet.
Bits related to subnet and interface addresses cannot be “mixed” (1111 0101.1100... - will not work).
Thus:
D&E classes (multicast classes): 224.0.0.0 - 225.255.255.255
And this is a complete list of possible subnet masks:
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Reserved IP addresses for use in local (not connected to the Internet, that is, which will NEVER be on the INTERNET) networks are as follows:
One class A network 10.0.0.0
· 16 class B networks 172.16.0.0 - 172.31.0.0
· 256 Class C networks 192.168.0.0 - 192.168.255.0
In addition, you cannot use the first and last addresses of each subnet to address machines. Because these addresses are network addresses and broadcast addresses.
A network address is an address in which the host address is all 0 (it is required for addressing the network itself), a broadcast address is, accordingly, all 1 (used when sending information to all members of the segment at once).
4.2 IP address settings
For our network, it is advisable to use class C networks, since the number of computers in the segments is small.
Two of our classrooms are combined into a common room (room No. 30), and the third is separate (room No. 36), the network of teachers’ cars is also a separate segment. Here are their addresses:
Audience No. 1: IP: 192.168.130.1 - 192.168.130.254
Mask: 255.255.255.0
Audience No. 2: IP: 192.168.230.1 - 192.168.230.254
Mask: 255.255.255.0
Audience No. 3: IP: 192.168.36.1 - 192.168.36.254
Mask: 255.255.255.0
“Teachers”: IP: 192.168.1.1 - 192.168.1.254
Mask: 255.255.255.0
The file server will be part of the teachers' subnet, its address is 192.168.1.254.
And the Internet server has two interfaces - one to the Teachers network, the other to the Internet, its addresses are 192.168.1.253 and an address with a mask allocated by the Internet provider.
Setting up a file server is not required except for installing the necessary programs and “opening” resources to the network.
In addition, each subnet is a separate group for ease of use of the network. In addition, employees will come up with names for groups and workstations themselves, again for their convenience.
4.3 Internet server setup
We decided to use Windows 2000 to run it because it is a proven, reliable operating system.
The settings for the network interface belonging to the teachers subnet will be as follows:
IP:192.168.1.253
Mask:255.255.255.0
The settings for the network interface connected to the Internet are provided by the provider, so we cannot describe them.
To configure the Internet server, we selected the UserGate program.
A complete guide to using and configuring UserGate is in Appendix No. 5.
network computer server file
4.4 File Server Settings
We decided to use Windows XP to run this server. This system is the most convenient for use on a file server.
Network interface settings:
IP:192.168.1.254
Mask:255.255.255.0
To make it easier to set up and administer the file server, we decided to open folders for access: folders with information not for students are password-protected, the rest are simply kept open for reading. And only one folder is open for full access without a password - a folder for students and their works.
To work on the network, you need to use programs that would speed up this process.
Here are some of them (use the latest versions of programs whenever possible):
1.Dr. Web (contains only antivirus)
2. Antivirus and Antihacker (firewall) of Kaspersky
3. Panda Antivirus (contains antivirus and firewall)
These are antiviruses - programs that prevent viruses from entering your computer, as well as remove, block and treat them. Install any of your choice.
I advise you to use a set of programs - “Lan Tricks”. All of these programs work together (LanScope has links to the others):
1. LanSafety - a program that allows you to prohibit the use of hidden resources.
2. LanScope - a program very convenient for scanning the network.
3. LanSend - a program that allows you to send messages to other users.
4. LanShutDown - a program that allows you to shut down computers on a network without using a server program.
There is another interesting collection of KillSoft programs:
1. KillCopy - downloading information over the network. A very convenient program - it allows you to download files in parts (i.e., if the connection is lost, the downloaded part of the file remains with you, in fully working condition).
2. KillWatcher - allows you to track your “visitors” and, if necessary, disconnect them from your resources. You can set the maximum number of simultaneous connections to your machine.
Active Ports - this program will be useful for administrators. A small but extremely useful tool that displays all open TCP/IP and UDP ports. It will also tell you which application uses which port. In addition, it will be useful for detecting Trojans and remote administration programs. Unfortunately only for NT/2k/2000/XP
DownLoad Master - One of the best and most convenient download managers. Excellent interface, complete user comfort, Russian language, many functions and absolutely free. allows you to significantly increase the speed of downloading files over the Internet using HTTP, HTTPS and FTP protocols.
RAdmin is a program for remote computer control. Useful for teachers to monitor students.
DU Meter is a small and simple program for monitoring traffic on your computer and issues warnings when the set limit is exceeded.
Bibliography
1. www.sinetic.ru
2. SoftDoc.ru - “building a local network”, Anton Lennikov.
3. A course of lectures on the discipline "Elements of the theory of information transmission."
4. A course of lectures on the subject “Networks”.
5. forum.ru-board.com
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For my course project, I chose the Ethernet network type.
Ethernet is a family of packet data transmission technologies for computer networks.
Ethernet standards define wire connections and electrical signals at the physical layer, frame formats and media access control protocols at the data link layer of the OSI model. Ethernet is primarily described by IEEE Group 802.3 standards. Ethernet became the most common LAN technology in the mid-1990s, displacing legacy technologies such as Arcnet and Token ring.
The name “Ethernet” (literally “ethereal network”) reflects the original principle of this technology: everything transmitted by one node is simultaneously received by all others (that is, there is some similarity to radio broadcasting). Nowadays, almost always the connection occurs through switches, so that frames sent by one node reach only the recipient (with the exception of transmissions to a broadcast address) - this increases the speed and security of the network.
The standard of the first versions (Ethernet v1.0 and Ethernet v2.0) indicated that coaxial cable was used as the transmission medium; later it became possible to use twisted pair and optical cable.
Advantages of using twisted pair cable over coaxial cable:
· ability to work in duplex mode;
· low cost of twisted pair cable;
· higher reliability of networks. when using a twisted pair cable, the network is built using a “star” topology, so a cable break only leads to a disruption in communication between two network objects connected by this cable (when using a coaxial cable, the network is built using a “common bus” topology, which requires terminal resistors at the ends cable, so a cable break leads to a malfunction of the network segment);
· the minimum permissible bending radius of the cable has been reduced;
· greater noise immunity due to the use of a differential signal;
· the ability to power low-power nodes via cable, for example, IP phones (Power over Ethernet, PoE standard);
· galvanic isolation of transformer type. In the CIS, where, as a rule, there is no grounding of computers, the use of coaxial cable often led to the failure of network cards as a result of electrical breakdown.
The reason for switching to optical cable was the need to increase the length of the segment without repeaters.
Access control method (for a network on a coaxial cable) - multiple access with carrier sensing and collision detection (CSMA/CD, Carrier Sense Multiple Access with Collision Detection), data transfer rate 10 Mbit/s, frame size from 64 to 1518 bytes, Data coding methods are described. The operating mode is half-duplex, that is, the node cannot simultaneously transmit and receive information. The number of nodes in one shared network segment is limited to a maximum of 1024 workstations (physical layer specifications may set more stringent restrictions, for example, no more than 30 workstations can be connected to a thin coaxial segment, and no more than 100 to a thick coaxial segment). However, a network built on a single shared segment becomes ineffective long before the limit on the number of nodes is reached, mainly due to the half-duplex mode of operation.
In 1995, the IEEE 802.3u Fast Ethernet standard with a speed of 100 Mbit/s was adopted and the ability to operate in full duplex mode became possible. In 1997, the IEEE 802.3z Gigabit Ethernet standard was adopted with a speed of 1000 Mbit/s for transmission over optical fiber and two years later for transmission over twisted pair cable.
Let's consider three popular network topologies, one of them will be used in my course project.
Star topology.
Fig.1 Star topology
A star is a basic computer network topology in which all computers on the network are connected to a central node (usually a switch), forming a physical segment of the network. Such a network segment can function either separately or as part of a complex network topology (usually a “tree”). All information exchange takes place exclusively through the central computer, which is subject to a very large load in this way, so it cannot do anything else except the network. As a rule, it is the central computer that is the most powerful, and it is on it that all functions for managing the exchange are assigned. No conflicts in a network with a star topology are possible in principle, because management is completely centralized
Advantages
· failure of one workstation does not affect the operation of the entire network as a whole;
· easy troubleshooting and network breaks;
· high network performance (subject to proper design);
· flexible administration options.
· One of the most common topologies because it is easy to maintain. Mainly used in networks where the carrier is UTP category 3 or 5 twisted pair cable.
Flaws
· failure of the central hub will result in the inoperability of the network (or network segment) as a whole;
· network installation often requires more cable than most other topologies;
· the finite number of workstations in a network (or network segment) is limited by the number of ports in the central hub.
Ring topology
Rice. 2 Ring topology
Ring topology (closed network topology) is a type of network topology in which all computers are connected by a communication channel closed on itself. In a ring, signals are transmitted in only one direction. The signal in the ring topology can be amplified.
Advantages:
· No possibility of collision of transmitted information.
· Possibility of simultaneous data transfer by several computers at once.
· Possibility of intermediate signal.
Flaws:
· High cost and complexity of maintenance.
· If the cable or computer fails, the network stops functioning.
· The ring is 2.5 times slower than the tire.
Bus topology
A bus topology is a topology in which all LAN devices are connected to a linear network data transmission medium. This linear medium is often called a channel, bus, or trace. Each device, such as a workstation or server, is independently connected to a common bus cable using a special connector. The bus cable must have a termination resistor, or terminator, at the end, which absorbs the electrical signal, preventing it from being reflected and moving in the opposite direction along the bus. When a source transmits signals into a network environment, they travel in both directions from the source. These signals are available to all devices on the LAN. As you already know from previous chapters, each device checks the passing data. If the destination MAC or IP address contained in the data packet does not match the corresponding address of this device, the data is ignored. If the MAC or IP address of the destination contained in the data packet matches the corresponding address of the device, then the data is copied by this device and transmitted to the data link and network layers of the OSI reference model. A terminator is installed at each end of the cable. When the signal reaches the end of the bus, it is absorbed by the terminator. This prevents the signal from being reflected and re-received by stations connected to the bus. To ensure that only one station is transmitting at a time, bus topology networks use a collision detection mechanism, otherwise a collision will occur if multiple stations attempt to transmit at the same time. If a collision occurs, the data from each device will interact with each other (ie, voltage pulses from each device will be present on the common bus at the same time), and thus the data from both devices will be damaged. The area of the network within which the packet was created and the collision occurred is called the collision domain. In a bus topology, if a device detects that a collision is occurring, the network adapter enters a delayed retransmission mode. Since the amount of delay before retransmission is determined by an algorithm, it will be different for each device on the network, thereby reducing the likelihood of a collision occurring again.
A bus topology is a topology in which all LAN devices are connected to a linear network data transmission medium. This linear medium is often called a channel, bus, or trace. Each device (for example, a workstation or server) is independently connected to a common bus cable using a special connector. The bus cable must have a termination resistor, or terminator, at the end, which absorbs the electrical signal, preventing it from being reflected and moving in the opposite direction along the bus.
Advantages
· Short network installation time;
· Cheap (requires shorter cable length and fewer network devices);
· Easy to set up;
· Failure of one workstation does not affect the operation of the entire network;
Flaws
· Network problems, such as a cable break or terminator failure, completely block the operation of the entire network;
· Difficulty in identifying faults;
· As new workstations are added, the overall network performance decreases.
In order to build a local network (LAN), you must first select a construction topology, on which the characteristics of the planned network will depend. The term "topology" reflects the physical arrangement of servers, workstations, computers, cables, and, if present, also the arrangement of switches, hubs and routers. In fact, in simple terms, it is a “map” of the network that is selected depending on the needs of the users. The choice of topology affects the composition and technical characteristics of network equipment, methods of system management and the possibility of further expansion of the network.
The basic topologies for building a LAN are the “bus” (bus), “ring” (ring) and “star” topologies.
In order to build a local network using the bus topology as a basis, it is necessary to connect all network devices to a common bus. A common bus will be used to exchange information between a node and another node.
The advantages of the topology are economical cable consumption, expandability, and ease of operation.
Disadvantages include a decrease in LAN throughput as traffic volumes increase, the difficulty of localizing a damaged area, and damage to the central cable will stop the work of a large number of users.
A local network built using a “ring” topology is a closed cable with nodes connected to it. The transmitted information passes along the ring in only one direction and is transmitted through each node connected to the LAN.
The advantages of the topology include the fact that the number of connected nodes does not affect the performance of the entire system, and all computers have equal access.
As disadvantages, it can be noted that damage to one of the nodes can affect the operation of the entire network.
Selecting a star topology determines that all nodes are connected to a central hub. Information from the transmitting node goes to all other computers through a hub.
The advantages of the topology are centralized control over the LAN and rapid expandability. Damage to one of the nodes will not affect the operation of the entire network.
The disadvantage of the topology is that if the hub fails, the entire network stops working.
In addition to the main types of topologies, hybrid and combined topologies are quite common, allowing you to fully cover all requirements for local network coverage.
Having compared all the above network topologies, we will use the “star” topology. A hierarchical star consists of a main switch to which the floor switches are connected. Workstations are connected to them.
After selecting the topology, we will present a plan for the placement of workstations indicating the location of switching equipment.
Figures 3.1, 3.2 show plans for the second and first floors of the school, where you can clearly see how the network will be built, where the computers, switches, server will be located and how they will be connected.
Figure 3.1 - Plan of the first floor of the building
Figure 3.2 - Plan of the second floor of the building
A diagram of the logical structuring of the network is shown in Figure 3.3.
Figure 3.3 - Logical network organization
In addition to choosing a network topology, the main requirements include:
1. Fault tolerance is one of the main factors that must be taken into account when building local networks.
If the school network fails, staff work may be disrupted and data may be lost.
In order to minimize the likelihood of network failure, they resort to several means:
- - duplication of power supplies;
- - possibility of “hot” replacement of components;
- - duplication of the control module;
- - duplication of switching matrix / bus;
- - use of several redundant connections;
- - use of Multi-LinkTrunk (MLT) and Split-MLT technology;
- - possible introduction of load balancing and duplication protocols at the routing level;
- - separation of channel ends;
- - channel spacing;
- - use of highly reliable equipment
- 2. Network controllability implies the ability to centrally control the state of the main network elements, identify and resolve problems that arise during network operation, perform performance analysis and plan network development. Ideally, network management tools are a system that monitors, controls and manages every element of the network - from the simplest to the most complex devices, and such a system views the network as a single whole, and not as a disparate collection of individual devices.
A good management system monitors the network and, when it detects a problem, initiates some action, corrects the situation, and notifies the administrator of what happened and what steps were taken. At the same time, the control system must accumulate data on the basis of which network development can be planned. Finally, the control system must be independent of the manufacturer and have a user-friendly interface that allows you to perform all actions from one console.
While solving tactical problems, administrators and technical staff are faced with the daily challenges of ensuring network functionality. These tasks require quick solutions; network maintenance personnel must quickly respond to fault messages received from users or automatic network management tools. More general issues of performance, network configuration, failure handling, and data security are gradually becoming visible, requiring a strategic approach, that is, network planning.
The usefulness of the management system is especially evident in large networks: corporate or public global ones. Without a management system, such networks require the presence of qualified operating specialists in every building in every city where network equipment is installed, which ultimately leads to the need to maintain a huge staff of maintenance personnel.
3. Scalability means that the network allows you to increase the number of nodes and the length of connections within a very wide range, while the network performance does not deteriorate. To ensure network scalability, it is necessary to use additional communication equipment and structure the network in a special way. For example, a multi-segment network built using switches and routers and having a hierarchical structure of connections has good scalability. Such a network can include several thousand computers and at the same time provide each network user with the required quality of service.
The choice of topology used depends on the conditions, tasks and capabilities, or is determined by the standard of the network used. The main factors influencing the choice of topology for building a network are:
information transmission medium (cable type);
medium access method;
maximum network length;
network bandwidth;
transfer method, etc.
Let's consider the option of building a network: based on Fast Ethernet technology.
This standard provides a data transfer rate of 100 Mbit/s and supports two types of transmission media - unshielded twisted pair and fiber optic cable. To describe the type of transmission medium, the following abbreviations are used, table.
Table 3. Fast Ethernet standard
100Base-T topology design rules.
100Base-TX.
Rule 1: The network topology must be a physical star topology with no branches or loops.
Rule 2: Category 5 or 5e cable must be used.
Rule 3: The class of repeaters used determines the number of hubs that can be cascaded.
- · Class 1. You can cascade (stack) up to 5 hubs using a special cascading cable.
- · Class 2: You can cascade (stack) only 2 hubs using twisted pair cable to connect the media-sensitive MDI ports of both hubs.
Rule 4: Segment length is limited to 100 meters.
Rule 5: The network diameter should not exceed 205 meters.
Rule 6: CSMA/CD access method.
100Base-FX.
Rule 1: The maximum distance between two devices is 2 kilometers for full-duplex communication and 412 meters for half-duplex for dial-up connections.
Rule 2: The distance between the hub and the end device should not exceed 208 meters.
There are several factors to consider when choosing the most appropriate topology for a given situation.
Table 4. Advantages and disadvantages of topologies.
|
Topology |
Advantages |
Flaws |
|
Economical cable consumption. Relatively inexpensive and easy to use transmission medium. Simplicity, reliability. Easy to expand |
With significant volumes of traffic, network throughput decreases. It is difficult to localize problems. Cable failure stops many users from working |
|
|
All computers have equal access. The number of users does not have any significant impact on performance |
The failure of one computer can bring down the entire network. It is difficult to localize problems. Changing the network configuration requires stopping the entire network |
|
|
It is easy to modify the network by adding new computers. Centralized control and management. The failure of one computer does not affect the functionality of the network |
Failure of the central node disables the entire network |
Based on all of the above, the optimal type of topology for the project is the 100Base-TX star topology with the CSMA/CD access method, since it is widely used these days, it is easy to modify and has high fault tolerance.
