What is a lan switch | We will be homemade. What is smart in smart wired commutators? We choose a switcher from the functions we need for work with traffic

Food and drink to encourage local merezhes to be presented to koristuvachs-nefahіvtsy more collapsible through a wide terminological vocabulary. Khabi and switches are painted in the folded hands, which guess telephone exchange, that creation of local home measure becomes a drive for training to specialists. Actually, it’s not such a terrible switch, as it’s called: the attachments are elementary nodes of the mesh, which allow for minimal functionality, which does not impair the knowledge of how the operation is installed and is fully accessible to the skin.

Appointment

Hub- Merezhey concentrator, the purpose of connecting computers to a single local network with additional connection of Ethernet cables.

Switch(switch - jumper) - a network switch, assigned to a local network of a number of computers via an Ethernet interface.

Porivnyannia

As a matter of fact, the difference between a hub and a switch is tied to the type of outbuildings: a hub and a switch. Irrespective of one task - organization local lines for the help of Ethernet - I’ll go to the top in a different way. The hub is the simplest rozgaluzhuvachem, which ensures direct communication between the customers of the city. The switch is a sensible attachment that distributes packages of data between clients in advance of the request.

The hub, taking the signal from one node, transmits it to all connected attachments, and then receives it again as the addressee: the computer is responsible for recognizing the packet itself. Zvichayno, vidpovіd transferring the same scheme. The signal torkaetsya all segments in the line, until you know which one to accept. Tsya furnishing reduces the throughput of the building of the merezhі (and the security of the exchange of data is clear). The switch, otrimuyuchi data package from the computer, sends it to itself for your address, as the bula was set by the manager, allowing for the least amount of traffic. Merezha, organized for the help of the switch, is important for safety: traffic exchange is carried out without intermediary between two clients, the other one cannot process the signal, there are no appointments. At the front of the hub, the switch secures the high throughput of the building of the created barrier.

Hub Logitec LAN-SW/PS

Switch Vimaga correct alignment tile map of the client computer: IP addresses and the mask of the subdivision owe one to one (the mask of the subdivision shows part of the IP address as the address of the border, and the other part - as the address of the client). The hub does not help, to that, which works on the physical OSI mesh model, broadcasting the signal. The switch works on the channel channel, allowing the exchange of data packets. Another feature of the hub is the ability to ensure the speed of transmission of data, focusing on the best displays.

Visnovki site

1. A hub is a hub, a switch is a switch.
2. The hub is the simplest, the switch is more "intellectual".
3. The hub transmits a signal to all the clients of the merezhі, the switch - only to the addressee.
4. Productivity of a measure organized through a switch, vishcha.
5. The switch ensures the highest level of safe transmission.
6. The hub is based on the physically tethered OSI model, the switch is on the channel.
7. The switch ensures the correct setting of the merging cards of the clients of the merging.

Logical topology Ethernet networks- the same tire with multiple access hot access up to one and the same middle transmission. What a logical topology means, how the nodes in the merezhі are looking over and shaping the frames that are being corrected and maintained in this merezhі. Tim is not smaller, at the same time practically in all Ethernet networks there is a physical topology of the “zirka” type or “expanded Zirka” type. This means that most of the Ethernet end devices sound connected to the LAN switch equal to 2 according to the point-to-point principle.

LAN switch layer 2 performs switching and filtering only based on the MAC address of the link layer of the OSI model. The commutator is more prozory for merezhevyh protocols and dodatkiv coristuvach. Line switch 2 creates a MAC address table, so that it can make a decision about packet forwarding. For transfers between independent IP subnets, level 2 switches rely on routers.

Switches select MAC-addresses for transmitting data through a network through their switching matrix to the outgoing port at the direct destination node. Switching matrix є іntegrovanі kanіlі і dopovnyuyut zapovnyuyut machine programming, scho allows kontrolіvvat sluzhennja danyah through kommutatorі. In order for the switcher to understand, which port must be selected to transmit the frame of a unicast connection, it is necessary to recognize it, as well as to the skin port.

The switch determines how the input frames are processed, changing the MAC-address table when using it. I create a MAC address table, adding the node's MAC address to it, as a connection to the skin port. Once the MAC address has been entered for the number of nodes connected to the first port, the switch can correct destinations for that node's traffic on the port that can be passed to the node for outward transmissions.

If the switch accepts a data frame, for which table there is no MAC address assigned, it will forward this frame to all ports, for the reason that this frame is accepted. If a node is recognized to be recognized, the switcher should enter the MAC address of the node in the address table, based on the data from the address field of the frame. At the borders with a large number of switches connected to the MAC-address table, the MAC-address of the ports is entered, which connects the switches, as if they display elements outside the boundaries of the node. As a rule, the ports of the switch, which are used to connect two switches, can use the MAC address entered in the input table.

In the past, the commutators won one of the offensive methods for switching data between neighboring ports:

Switching from buffering

Switching without buffering

When switching with buffering, if the switch takes a frame, it will take data from the buffer until the entire frame is taken. Under the hour of saving, the commutator analyzes the frame in order to take information about the recipients. In this case, the switch also overrides pardons, victorious to the end part of the Ethernet frame of cyclic control over the environment (CRC).

In case of non-buffered switching, the switch will process the data in the world, it should be inadvertently, as the transfer has not yet been completed. The switch adds to the buffer the same number of frames, as it is necessary for reading the MAC address of the recognition, so that the vin can be assigned to which port to transfer the data. The MAC address assigned is specified in 6 bytes of the frame after the preamble. The switch listens to the MAC address of recognition from its switching table, assigns the port of the outgoing interface and directs the frame to its node of recognition through the switch's vision port. The commutator does not change the frame for the presence of any pardons. Oskіlki switcher does not need to add a check to the buffer of the entire frame, and with this vin it does not recheck pardons, switching without buffering is more convenient, lower switching with buffering. Tim is not smaller, the switches don’t check pardons, they send poor staff in all directions. In case of transferring personnel, the throughput of the building will be changed. Zreshtoy merezheva fee recognized vіdhilyaє poshkodzhenі cadres.

Modular switches to propagate the great flexibility of the configuration. As a rule, stinks are supplied with a different size, which allows you to install a small number of modular line cards. Ports are actually placed on line cards. The line card is inserted into the switch chassis similar to expansion cards that are installed in a PC. The bigger the chassis, the more modules it will support. As shown on the little one, on the vibrate the impersonal rozmіrіv shasi are propagated. If you add a modular switch with a 24-port line card, you can easily install one of the same card, as a result of which the total number of ports will be increased to 48.

This division represents the technologies that are used in outbuildings, which are inaccurately called bridgesі switches. The topics that are suggested here include the specifics of the principles of operation of channel attachments, local and remote bridges, ATM switching and local networks. The next part was divided into Part 4, "Bridges and Switches" and this book is dedicated to the specifics of these technologies in more detail.

What is Mosti ta Komutatori?

Bridges and commutators are built-in data communications, which work in principle on a par with the 2nd OSI reference model. Like this, the stench wafts up to the outbuildings of the canal line.

Bridges became commercially available on the cob in the 1980s. At the time of their introduction, the bridges were closed and allowed to reseal bags between homogeneous meshes. Recently, the construction of bridges between different barriers was also designated and standardized.

Deyakі types of bridges have become important like intermertsevі outbuildings. Transparent Bridge communicate with us in front of Ethernet environments, as well as bridges with pre-routing (source-route bridge) blame us in front of the middle of Marker Ring (Token Ring). Translational Bridge ensure broadcasting between formats and principles of transit. different types middles (sing token ring and Ethernet). Zreshtoyu, gaps with pre-routing (source-route transparent bridge) combine the algorithms of transparent and pre-routed bridges to enable communication in different Ethernet/Token Ring environments.

Today's switching technology has become a revolutionary successor of intermer solutions based on bridges. Zastosuvannya commutators at the same time dominated the appendages, de bridges were blocked in the early expansions of the merezhi. Miraculous throughput productivity, more port space, less space per port and more flexibility contributed to the appearance of commutators as a replacement technology for bridges and an addition to routing technology.

View of the outbuildings of the canal level

If the bridges and commutators add more characteristic features, the features of the technology will be improved. The switches work much more quickly, the oscillators switch hardware, as well as switch bridges programmatically, and they can also connect local networks with a nervous smog of transmission. For example, behind the help of a switch, you can connect local networks of 10- and 100-megabit Ethernet. The switches also support more port widths and lower bridges. Deyakі kommutatori pіdtrimuyut usіchenu (cut-through) commutаtіyu, scho nizhuє zatrimіnnya zatrimі v merezhі, yakіkі yak pontіmіuyut lich sіchennuyu (store-and-forward) komutаtsіyu. Nareshti, commutators reduce collisions in the mesh segments, the shards ensure the sight of the passage of the skin segment of the mesh.

Types of bridges

The commutator is one of the most important outbuildings, which are used in case of local fencing. In these articles, we can talk about how commutators are used and we are based on important characteristics, which are necessary to protect when choosing a local network commutator.

On the back, we can look at the overall structural scheme, abi to understand how the commutator borrows space from the local enterprise.

The widest one is shown on the little one block diagram small local area. As a rule, such local networks have access switches.

Access switches without intermediary connection to end-of-line networks, giving them access to local resources.

However, the great local networks of commutators have the following functions:

Riven access to the border. As it was assigned to a higher commutator and access to provide connection points for the extension of the terminal box. At great local networks, the frames of the access switches are not interchanged one by one, but are transmitted through the switches to the distribution.

Riven rozpodіlu. The switches of this level transfer traffic between the access switches, but in case of this they do not interact with the terminal boxes.

System kernel riven. Attached this type to unite the data transmission channels of the types of commutators equal to the distribution at the great territorial local borders and to ensure the high level of commutation of the data flows.

The switches are:

Non-kerned switches. These are the main autonomous extensions in the local area, so as to manage the transfer of data independently and not to be able to dodatkovy nalashtuvannya. Due to the ease of installation and low price, a wide width was created for installation in home minds and small businesses.

Kerovani commutators. Bigger slips and expensive outbuildings. Allow the administrator of the merezhі to independently adjust their tasks.

Kerovany switches can be fixed in one of the following ways:

Through the console port Via WEB interface

Through Telnet Via SNMP protocol

Through SSH

equal switches

All switches can be divided into different models OSI . The commutator may be able to do this with greater possibilities, however, the versatility of yoga will be significant.

Switch 1 equal (layer 1). Before given equal you can add habi, repetitions and other attachments that are physically practiced. The buildings were built on the cob for the development of the Internet and at the given hour in the local area do not win. Otrimavshi signal attachments of this type, just transmit yogo far away, at all ports, Crimean ports

Commutators 2 equals (layaer2). Up to which level one can see non-ceramized that part of the ceramic commutators ( switch ) working on the channel equal model OSI . Switches of another equal work from frames - frames: a stream of data broken into portions. Having taken the frame of the switch equal 2, change the frame to the address of the manager and enter it in your table MAC address, setting this address to the port on which wine the frame was taken. For such an approach, the switches of another equal send data only to the port of the owner, not working with their excess traffic on other ports. Switches of another equal do not know IP address of placement on the third twill line model OSI that practice is less on the canal level.

Switches of another peer support the following widest protocols, such as:

IEEE 802.1 q or VLAN virtual local networks. This protocol allows, within the framework of one physical dimension, to create other logical dimensions.

For example, add-ons are connected to one switch, but they can be found in different VLAN not to chat one to one and transfer data can only be done at your own wide domain (attachments from these VLANs). Between themselves, the computers for the little one can more easily transfer data for an additional outbuilding, which works on the third equal. IP addresses: router.

IEEE 802.1p (Priority tags ). This protocol is present at the protocol IEEE 802.1 q and 3 bit field from 0 to 7. The Danish protocol allows marking and sorting all traffic according to the level of importance and prioritization (maximum priority is 7). Framey with great priority to overcome us in front.

IEEE 802.1d spanning tree protocol (STP).This protocol vibudovuє local merezh in a tree-like structure, schob niknut zakіltsovuvannya merezha and zabigt avtobytnya tiring storm.

It is permissible to install local chimneys at the sight of the ring to increase the resistance to the top of the system. The switch with the highest priority in the merezhі is selected as the root (Root).At the butt of the induced SW3, it is rooted. Not zagliblyuyuchis at algorithms vikonanny protocol, commutators calculate the way from the maximum price and block yoga. For example, in our case, the shortest path from SW3 to SW1 and SW2 will be through the power interface (DP) Fa 0/1 and Fa 0/2. In this case, the price for promotion for a 100 Mb/s interface will be 19. The interface Fa 0/1 of the switch SW1 of the local network is blocked by the fact that the price for the promotion of the route will be added up for two transitions between 100 Mb/s interfaces 38+19=19.

Even though the working route will be broken, the commutators will clear the way and unblock the whole port

IEEE 802.1w Rapid spanning tree protocol (RSTP).Enhancements 802.1 standard d , which may be more high stability and less hour of renewal of the line zv'yazku.

IEEE 802.1s Multiple spanning tree protocol.The rest of the version, like a vrakhovu all the shortcomings of the protocols STP and RSTP.

IEEE 802.3ad Link aggregation for parallel link.This protocol allows to unite porti groups. The total dryness of this port of aggregation is formed from the sum of the dryness of the skin port in it.The maximum speed is set by the IEEE 802.3ad standard and is 8 Gb/s.

Switchers 3 equals (layer3). These attachments are also called multiswitches so that they stink at their own commutators, which work on another level and routers, which work with IP packages to the third equal.Level 3 switches cover all functions and standards of level 2 switches. Third devices can handle IP addresses. The switch 3 equals to support the installation of various devices: l 2 tp, pptp, pppoe, vpn etc.

Commutators 4 rubles (Layer 4) . Attachment level L4 models, which work on the transport level OSI . Ensure the reliability of transmission. Qi switches can on the basis of the information from the headers in the packets to understand the belonging of the traffic life supplements and make a decision about redirecting such traffic to the substantiation of this information. The name of such outbuildings did not stand up, and sometimes they are called intelligent switches or L4 switches.

Main characteristics of commutators

Number of ports. In the given hour, switchers are installed with a number of ports from 5 to 48. Depending on this parameter, a number of outbuildings can be deposited, so you can connect to a switch.

For example, with a small local network of 15 computers, we need a switch with 16 ports: 15 to connect the end of the outbuildings and one to install that router connection to access the Internet.

Data transmission speed. Tse shvidk_st, de pratsyuє leather port of the switch. Sound the speed as follows: 10/100/1000 Mb/s. The speed of the work and the port is determined by the process of auto service with the end of the building. For kerosene switches, this parameter can be adjusted manually.

For example: Client attachment of a PC with a 1 Gb/s mesh board connected to the switch port with a 10/100 Mb/s operating speed c . As a result of the automobile service, the house will be built to achieve the maximum possible speed of 100 Mb/s.

Auto service to the port mizh Full - duplex and half - duplex. Full-duplex: the transfer of data is immediately zdіysnyuєtsya at two straight lines. half-duplex the transfer of data is carried out sequentially in one, then in the other directly sequentially.

Internal throughput capacity switching matrix. Tsey parameter show, with some kind of hot code, the commutator can process data from the other ports.

For example: a local network has a commutator for some 5 ports, which works on the speed of 10/100 Mbit/s. AT technical characteristics parameter switching matrix is ​​more expensive 1 Gbit/ c . This means that the skin port is in mode. Full-duplex you can use 200 Mbit/ c (100 Mb/s up and 100 Mb/s up). It is possible that the switch matrix parameter is less than the specified one. This means that at the time of peak demand, porters cannot work out of the declared speed of 100 Mb/s.

Auto fit MDI/MDI-X cable type. This function allows you to designate in two ways the bula is wrapped in a twisted pair of EIA/TIA-568A or EIA/TIA-568B. When installing local lines of the largest width, the EIA / TIA-568B scheme was installed.

Stacking - Tse uniting a number of commutators into one single logical extension. Different types of switch makers use their own technologies for stacking, for example c isco vicorist stacking technology Stack Wise from bus between switches 32 Gb/s and Stack Wise Plus from bus between switches 64 Gb/s.

For example, this technology is relevant for large local networks, it is necessary to connect more than 48 ports on the basis of one building.

Fixing for 19” rack. In home minds and small local tethers, switches are often installed on even surfaces or fastened to the wall, so the presence of the so-called “wuh” is necessary in large local tethers and is actively located in server closets.

MAC Table Dimensionthe address. The commutator (switch) is attached, which works on 2 equal models. OSI . On the hub view, which simply redirects the frame from all ports to the port of the source, the switch starts: remember MAC I will add a porter to the address, bringing it in, I will write down the port number and hour of life to the table. vicorist qiu table the switch redirects the frame not to all port, only to the owner port. As in the local area, the number of outbuildings significantly increases the number of reordering tables, the commutator starts to overwrite the old entries in the tables and writes new ones, which significantly reduces the speed of the commutator's operation.

jumbo frame . This function allows the switch to work with a larger packet size, lower is designated by the Ethernet standard. After receiving the skin pack, one hour is spent on yoga. If you win a larger packet size using Jumbo Frame technology, you can save an hour for processing the packet in batches, de-bouncing the data transmission speed of 1 Gb / s and more. For less speed, I won't win the great

Switching modes.In order to understand the principle of robotic switching modes, let's take a look at the structure of the frame that is transmitted on the channel line between the borders and by the switch at the local border:

As can be seen from the little one:

• The start of the preamble signals the start of the transfer to the frame,
• Potim MAC recognition addresses ( DA) and MAC addresses of the source ( SA)
• Third level identifier: IPv 4 or IPv 6 win
payload)
• І nasamkinets control sum FCS: 4 byte CRC value, which is used to detect transmission pardons. Calculated by the party that rules and is placed in the FCS field. The receiving party calculates given value independent and similar to the otrimanim meanings.

Now let's look at the switching modes:

Store-and-forward. Tsey mode Switching saves a frame from the buffer over and overrides the field FCS , as it is located on the very end of the frame, and as the control sum of the field does not run, the entire frame is displayed. As a result, the amount of time spent on vanishing at the border is reduced, so that it is possible to pick up frames with a pardon and change the hour of the packet transfer. Given technology present in road commutators.

cut through. Simple technology. AT to this particular type frames can be processed more quickly, so that they do not need to buffer more. For analysis, data is taken into the buffer from the beginning of the frame up to the recognition MAC address (DA) inclusive. The switch reads the MAC address and redirects to the destination. The shortcomings of this technology are those that the switch overpowers at times as dwarf, less than 512 bit intervals, and slower packets, increasing the burden on the local network.

Support for PoE technology

Pover over ethernet technology allows you to power an external device over that cable. Decision allows you to spend pennies on additional installation of line living.

There are also PoE standards:

PoE 802.3af supports power up to 15.4W

PoE 802.3at supports power up to 30W

Passive PoE

PoE 802.3 af/at may have intelligent control circuits for power supply to attachments: the first lower power supply to the attachments PoE dzherelo standard af/at vyroblya uzgodzhennia with it, so that it can be protected from the attachment. Passiv PoE is significantly cheaper than the first two standards mesh cable without any weather.

Characteristics of standards

The PoE 802.3af standard is supported by most inexpensive IP video cameras, IP telephones and access points.

The PoE 802.3at standard is present in the expensive models of IP cameras, video warning, it cannot be invested in 15.4 watts. I have an IP video camera, so I have a PoE (switch) to comply with this standard.

Extension slots. The switches can have additional expansion slots. The most expandable are SFP modules (Small Form-factor Pluggable). Modular, compact receivers that are designed to transmit data to a telecommunication medium.

SFP modules are inserted at the right port of the SFP router, switch, multiplexer or media converter. Want to install SFP Ethernet modules, usuallyfiber optic modules are used to connect to the main channel when transmitting data on large distances, inaccessible to the Ethernet standard. SFP modules are selected depending on the security of data transmission. The most wide-ranging are dual-fiber SFP modules, which use one fiber to receive, otherwise transmit data. However, WDM technology makes it possible to transmit data on different devices over a single optical cable.

SFP modules are:

• The SX-850 nm is wired with a multi-modal optical cable for a distance of up to 550m.
• LX - 1310 nm works with both types of optical cable (SM and MM) for distances up to 10 km.
• BX - 1310/1550 nm works with both types of optical cable (SM and MM) for distances up to 10 km.
• XD - 1550 nm wiping with single-mode cable up to 40 km, ZX up to 80 km, EZ or EZX up to 120 km and DWDM

The SFP standard itself transmits data transmission with a speed of 1Gb/s or with a speed of 100 Mb/s. For more data transfers, SFP+ modules have been expanded:

• SFP+ data transmission with 10 Gb/s speed
• XFP data transfer with 10 Gb/s speed
• QSFP+ data transmission with 40 Gb/s
• CFP data transfer with 100 Gb/s speed

However, at higher speeds, signal processing is carried out high frequencies. Tse will require more heat and, apparently, large dimensions. Therefore, Vlasne, the SFP form factor was saved from SFP + modules.

Visnovok

A lot of chitachiv singsongly clung to non-ceramic switches and budgetary ceramic switches of a different level in small local areas. However, the selection of commutators to encourage greater and technically foldable local lines is better given to professionals.

Bezpechna Kuban for an hour of installation of local networks of vicorist switches and offensive brands:

Professional solution:

Cisco

Qtech

Budget solution

D-Link

Tp Link

Tenda

Bezpechna Kuban vykonuє installation, commissioning and maintenance of local lines in Krasnodar and Pivdnі Russia.

03/18/1997 Dmitro Ganzha

The commutators occupy the central space of the modern local networks. TYPES OF SWITCHES HUB RISC AND ASIC PACKET PROCESSING ARCHITECTURE OF HIGH-CLASS SWITCHES modern technologies.

The commutators occupy the central space of the modern local networks.

Switching is one of the most popular modern technologies. Switches connect bridges and routers to the periphery of local networks, depriving them of the role of organizing communication through the global network. Such popularity of commutators is slandered in pershu tim, that they allow for micro-segmentation rahunok to increase the productivity of the meshes in porous meshes that are divided, with the same nominal throughput building. Krim podіlu merezhі on drіbnі segments, commutators give mozhlivіst organіzuvat podklyuchenі prіstroї in logicalіchі merezhі and easily regroup їх, if necessary; otherwise, apparently, they allow you to create virtual measures.

What is a commutator? Згідно з визначенням IDC, "комутатор - це пристрій, конструктивно виконаний у вигляді концентратора і діє як високошвидкісний багатопортовий міст; вбудований механізм комутації дозволяє здійснювати сегментування локальної мережі та виділяти смугу пропускання кінцевим станціям в мережі" (див. статтю М. Кульгіна "Побудувати мережу plant a tree..." at the lute room LAN). However, the appointment is carried out by us in front of the commutators of personnel.

TYPES OF COMMUTATION

Under the commutation, sound out the minds of different technologies - configuration commutation, commutation of personnel, commutation of middle and middle ones, and transformation between personnel and middle ones.

Switching configuration in the house is the same as port switching, and a specific port on the smart hub module is assigned to one of the internal Ethernet segments (or Token Ring). Tse recognition zdiisnyuetsya in the distant rank for help program management merezhey when connected or moved koristuvachiv and resources at the merezha. On the basis of other switching technologies, this method does not increase the productivity of local networks.

Frame switching or switching in a local network using standard Ethernet frame formats (or Token Ring). The skin frame is processed by the nearest commutator and transmitted further through the mesh without interruption. As a result, the merging transforms like a bi into a collection of parallel high-profile straight channels. Those, how the commutation of personnel in the middle of the commutator, is easier to look at below on the butt of the concentrator, which are commutated.

Intermediate switching is done in ATM. The choice of small medium-sized fixed assets gives the opportunity to create inexpensive high-voltage switching structures on the hardware level. І staff commutators, and mid-range commutators can support a small number of independent working groups independently from their physical connection (div. division "Pobudova virtual networks").

Interchange between frames and in the middle allows, for example, stations with an Ethernet board to interact without intermediary with ATM devices. Tsya tekhnologiya zastosovuetsya pіd hаmіlії ї ї ї ї ї ї rezhі.

At this school, we are in front of the staff commutation.

SWITCHING HUB

The first switching hub, called EtherSwictch, was presented by Kalpana. This concentrator allowed to reduce the competition among the merchants for the speed of the number of knots in the logical segment for the help of micro-segmentation technology. In fact, the number of stations in one segment was shortened to two: the station that initiated the request, the station that confirmed the request. No other station will not process information that is transmitted between them. Packets are transmitted across the bridge, but without the power of the bridge zatrimki.

At the Ethernet network that communicates, a skin member of a group of dekilkoh koristuvachiv can be guaranteed a throughput of 10 Mbit/s at once. To understand how such a concentrator works, the best help is the analogy of the famous old telephone switchboard, for which participants in the dialogue have a coaxial cable. If the subscriber calls for "everyday" 07 and asks for a call with such a number, the operator first checks for everything, which line is available; if so, then vin z'ednuvat uchasnikiv without intermediary for the help of the cable cable. Nobody else (behind the vinnyatka of the special services, zrozumіlo) was not able to rozmov a little bit. After completion of the move, the operator opened the cable to both ports and check for the next week.

Switching hubs is similar (div. Figure 1): they transfer packets from the input port to the output port through the switching matrix. If a packet is sent to an input port, the switch reads its MAC address (that is, the address of another equal), and it is redirected to the port that matches that address. As a port of employment, then the package is sent to the black. In fact, the black is a buffer on the input port, de packets are checked, if the required port is called. Prote buffering methods are being challenged.

Little one 1.
Switching hubs function similarly to many telephone switches: they plug the inlet port directly with the outgoing through the switching matrix.

PACKAGE PROCESSING METHODS

In case of cross-connection (also called switching on the fly and switching without intermediate buffering), the switch reads only the address of the packet to be reached. The package is transferred far and wide, depending on the availability of the new pardon. This allows you to significantly speed up the processing of the packet, the shards are read only a little bit of the first bytes. It is the fault of the receiving party that it is the fault of the defective packets and requesting their retransmission. However, modern cable systems are needed, so the need for re-transmission in bags is minimal. Tim is not smaller, there is no insurance against pardons at the time of a broken cable, malfunctions to pay chi shift code from the right electromagnetic dzherel.

When switching with intermediate buffering, the switcher, while accepting a packet, does not transmit further until it has read the rest, otherwise it has not read all the necessary information. Vіn is no longer assigned to the owner's address, but also to check the checksum, i.e. you can find defective packets. Tse allows you to isolate how to generate a pardon segment. In this rank, the commutation with intermediate buffering is deafening to superiority, and not to swiftness.

Krim two perekahovanyh vishche, deyakі commutator vikoristovuyut hybrid method. In savvy minds, the stink of zdіysnyuyut skrіznu komatsiyu, but if so, stalking for a few pardons from looking at the reverification of the control sums. If a number of pardons reach a predetermined threshold value, the stink will switch to the switching mode from intermediate buffering. When the number of pardons is reduced to an acceptable level, the stench turns into a direct switching mode. This type of switching is called threshold or adaptive switching.

RISC and ASIC

Most of the switches with intermediate buffering are implemented on the basis of standard RISC processors. One of the advantages of such an approach is that it is notably cheap compared to switches with ASIC integrated circuits, proteins are no different than those of different specialized add-ons. Switching in such outbuildings is required for help software Therefore, their functionality can be changed for additional modernization of the installed firmware. It’s not enough for those who stink more for switches based on ASIC.

Switches with ASIC integrated circuits are recognized for viconan specialists: all functionality is "protected" in the hardware security. This approach has a shortcoming: if modernization is necessary, the vibration picker will rework the scheme. ASIC sound zdіysnyuyut skrіznu commutation. The ASIC switching matrix creates a physical path between the incoming and outgoing ports, as shown in .

ARCHITECTURE OF SWITCHES IN THE SENIOR CLASS

High-end switches have, as a rule, a modular structure, and stinks can be used both for packet switching and for middle-class switching. Modules of such a commutator zdіysnyuyut commutation between merezhami different types, Including Ethernet, Fast Ethernet, Token Ring, FDDI and ATM. Whereas the main switching mechanism of such attachments is the ATM switching structure. Let's take a look at the architecture of such attachments on the Centillion 100 butt of the Bay Networks company.

Switching is carried out for the help of the advancing three hardware components (div. baby 2):

(1x1)

Figure 2.
In high-end switchers, switching occurs more and more often high speed and ease of migration to ATM.

The skin switch module can port I/O, buffer memory and the CellManager ASIC. In addition, the skin module for local media may have a RISC processor for switching frames between local ports and picking / picking packets for converting frames and midpoints one to one. All modules can independently establish switching between their ports, so only traffic assigned to other modules is transmitted through the connection panel.

The skin module supports the address table, and the main processor turns them into one single table, for good reason okremium module maybe bachiti merezh zagalom. For example, if the Ethernet module accepts a packet, it determines to whom the packet is addressed. As the addresses are changed from the local address table, the RISC processor will switch the packet between the local ports. If the addressee is on another module, then the picker / picker will convert the package to the box. The CellManager specifies a destination mask to identify the module(s) and port(s) that are to be assigned to the core target. Skin module, pay mask bit of any destination mass task, copy the middle to the local memory and transfer data to the output port to the specified port mask bit.

ENCOURAGING VIRTUAL MERGE

Crime for increasing productivity, commutators allow you to create virtual networks. One of the methods of creating a virtual network is to create a wide-range domain behind an additional logical port in the middle of the physical infrastructure of the communication extension (it can also be a smart hub - a configuration switch, so a switcher - a switch). For example, unpaired ports of an eight-port outbuilding are assigned to one virtual line, and guys - to another. As a result, the station in one virtual area appears isolated from the stations to the other. The disadvantage of such a method of organizing a virtual fence is that all stations connected to one and the same port are guilty of lying up to one virtual fence.

Another way to create a virtual network is based on the MAC addresses of connected devices. With this method of organizing a virtual network, be it a spivrobitnik can connect, for example, your laptop computer to any port of the switch, and the vin will automatically assign the validity of the first port to another virtual network based on the MAC address. This method also allows coristuvachas, connected to one port of the switch, to lie up to different virtual borders. Report about virtual arrays of divs. article by A. Avduevskiy "Such real virtual measures" in the birch LAN issue for this region.

SWITCHING OF THE THIRD RIVNYA

For all their successes, the commutators suffer one stout shortfall: the stench is not able to protect the measure from avalanches of wide packets, but only to the point of unproductive entanglement of the measure and an increase in the hour of the day. Routers can control and filter non-required wide traffic, but stinks can be an order of magnitude better. So, according to the documentation of Case Technologies, the typical productivity of the router is 10,000 packets per second, but the price is not equal to that of the switch - 600,000 packets per second.

As a result, a lot of virobniks began to be introduced into the switcher and the routing functions. If the robot of the commutator did not suffice, there are different methods: for example, switching of another level, and switching of the third level are implemented without intermediary hardware security(In ASIC integrated circuits). Different companies call this technology in different ways, but there is only one meta: the routing switch is guilty of violating the functions of the third level from the same security, which are the functions of another level. An important factor is the price of such an addition to the port: it is also due to the low cost, like that of the commutators (div. article by Nick Lipps in the next issue of the LAN magazine).

WISNOVOK

Switches are both structurally and functionally different; in one small article it is impossible to miss all aspects of it. In the coming years, the ATM switcher is reported to be visible.

Dmitro Ganzha is a senior editor at LAN. You can contact him at: [email protected].

Switches in the local area