FDDI technology. Characteristics of FDDI technology

⁰

Token Ring and FDDI technologies can be significantly more complex implementation than the same Ethernet technology on shared data environment. The greater number of folds has led to the fact that retailers can change the category to the full efficiency of technology: to greater tolerance, conforming to the friendly design of priority service specific data packets, this as voice traffic, which is sensitive. In this stench, for the butt, a larger version of the current cut, FDDI only for a tribal hour were victorious like a campus backbone of a company.

Data transfer rate in Token Ring networks

For a sub-bag, the flow period is 4 Mb/s, if you are the first company to expand in IBM, then we will remain 16 Mb/s. Strength in local networks was the same in Ethernet technology, so MAC-addresses are the same.

Network access method

At Token Ring, there are some measures for specifying the sequence of notifications, so that you can access to the transmission of media for an additional special frame - token, or token. Token Ring technology has ring topology and token is passed from node to node in one direction. Note that owns token has the right to broadcast information in the shared data environment. Thus, there are no conflicts in the shared data environment, but are present in the Ethernet technology. There is also an hour of exchange for the power of the current to the node may not monopolistically fully capture all network resources. If the hour of the settlement node transmits the token neighbor node.

Transfer token in the Token Ring between nodes

The problem of transmission of delay-sensitive traffic is solved by prioritizing training. Transmitting node sets the priority of each frame. Also, token itself is always a certain level of priority at any given time.

FDDI technology

Technologists FDDI is an advanced version of Token Ring technology. There is also a twist on topology and transfer of the token from node to node. A difference is that FDDI operates at high speed and ha better mechanism to ensure fault tolerance. Also this is the first technology that started using optical fiber. Optical fiber is used as the start time with the 70-ies of the last century.

Transfer token in FDDI

This technology has two brackets for data transmission. The first end is the main and all transportation, translation and secondary services. One of them seems to be missing. Nearby cities have spent transport to another end and end of topology for a short backup path. Formed flat ring topology.

Merezha FDDI. The speed of 10 Mbit / s is not enough for a bagatioh current merezh. That is why technologies and specific implementations of high-shear scrap are being developed.

FDDI (Fiber Distributed Data Interface) - LOM of the ring structure, which is based on fiber optic fiber and a specific version of the marker access method.

In the main variant of the line, a subwire ring on the FOCL was planted. Security of information is 100 Mb/s. Between extreme nodes up to 200 km, between land stations - three more than 2 km. The maximum number of knots is 500. VOLZ has vicorous vines of 1300 nm.

Two rings of VOLZ are victorious at the same time. Stations can be connected up to one per station or both at a time. By using a specific node, both networks allow for a total throughput of 200 Mbps at each node. It is more possible to win another village - go around for help from a poor house (Fig. 4.5).

Mal. 4.5. FOCL ring near FDDI

FDDI has the original code and access method. The code of the NRZ type is set (without turning to zero), in any change of polarity in the next cycle, it is accepted as 1 day of change of polarity as 0. The code will be self-synchronizing, after the skin choir bits of the transmission, the synchronizing difference will fluctuate .

Such a special Manchester code is called 4b / 5b. Record 4b / 5b means a code, in which for self-synchronization when transmitting 4 bits of a binary code, 5 bits are changed so that there can not be more than two zeros after the last, or after 4 bits, one more language difference is added, which is broken be in FDDI.

With this code, the coding and decoding blocks are folded up, then the transmission speed of the link line is increased, the shards may be changed in the maximum frequency of the retransmission with the Manchester code.

Appropriate to the FDDI method according to the number of the circulating packet, which is composed of a marker and information frames. Whether the station is ready before transmission, recognizing the packet to pass through it, enter your frame at the end of the packet. Won likvіduє yogo after that, as the frame turns to it, after the turn of the ring, you should know that you won't take possession of it. If the exchange is carried out without problems, then the frame, which turns to the station-repairman, is put in the first package, the shards of all the front frames may be canceled earlier.

Merezha FDDI sound vikoristovuєtsya like a richly okremih p_dmerezh SCRAP, scho combined into a single merezha. For example, when organizing an information system of a great enterprise, the mother LOM type Ethernet or Token Ring is used for okremy project sub-projects, and the communication between the sub-projects is carried out through the FDDI measure.

Fiber Distribution Data Interface or FDDI was created in the mid-80s, especially for the union of the most important businesses. If for a working station the speed of transmission at 10 Mbit / s was miraculous, then inter-server communications were clearly insufficient. Depending on the needs, FDDI is designed to communicate between servers and other important dealers, and transferring the ability to transfer by the process of transferring that high level of trust. This is the main reason, through the yak vin dosі borrowing such a commemorative place on the market.

On the Ethernet port, FDDI victorious ring structure, de-attachments are united in a large ring and transmit data sequentially one to one. The package can go more, lower through 100 nodes, first lower to the addressee. But do not confuse FDDI from Token Ring! Token Ring wins only one token, which is passed from one machine to another. FDDI wins another idea - so the ranks of the hour marker. The leather machine overpowers the tribute of the offensive stretching of the singing period to the hour, about what kind of stench they are housed behind the back if they are connected to the kiltsya. Stations can send packets one hour, and still allow an hour.

The rest of the machine is not responsible for the check, while the transmission medium is ringing, then the packet size can reach 20000 bytes, if you want more victorious packets with a size of 4500 bytes, or even more for the Ethernet packet. Tim is not smaller, as the assignment package for the work station, connected to the loop for additional Ethernet, is not larger than 1516 bytes.

One of the biggest advantages of FDDI is its high arrogance. Sounds like wine is added up for two more rings. The leather machine can take away that nadsilat and podomlennya to your two vessels. Tsya scheme allows the functioning of the meshes, winding up as if the cable was broken. If the cable is torn, the extensions on both ends are repaired as a plug and the system continues to function as one ring, as if to pass through the skin of the extensions. If the skins of a specific route of one-way directing and extensions transmit data from the appointments of the hour, then such a scheme will basically include collisions. This allows FDDI to achieve practically the theoretical throughput, as in fact, to become 99% of the theoretically possible data transmission speed. The high arrogance of the podvyyny kіltsya for the mind, more than said, zmushuє spozhivachіv prodzhuvat kupuvat obladnannya FDDI.

The principle of diversification of FDDI Merezha FDDI is a fiber-optic marker ring with a data transfer rate of 100 Mbit/s. The FDDI standard was developed by Committee X3T9.5 of the American National Standards Institute (ANSI). Merezhі FDDI are supported by all leading breeders of the fencing system. In this hour, the ANSI X3T9.5 committee renames to X3T12. Vikoristannya, as the middle of the expansion of fiber optics, allows you to expand the amount of cable transmission and increase the distance between the framing outbuildings. The bandwidth of the FDDI and Ethernet network will be equal if it is secured for a lot of short-term access. The permissible level of utilization of the Ethernet network lies at the borders of 35% (3.5 Mbit / s) depending on the maximum throughput capacity (10 Mbit / s), in the other case, the efficiency of the cycle is not high and the throughput capacity of the cable is to decrease. For FDDI merezhes, utilization can reach 90-95% (90-95 Mbps). In this way, the capacity of FDDI is about 25 times greater. The nature of the FDDI protocol is determined (the ability to transfer the maximum delay when transmitting a packet as it is, and the ability to ensure the guaranteed amount of bandwidth for the skin stations) to make it ideal for vikoristannya in the network automated control systems for the real hour and for addendums that are critical for the hour of transmission of information (for example, to transfer video and sound information). FDDI lost a lot of its key powers into the Token Ring (IEEE 802.5 standard). Nasampered - tse kіltseva topology and marker method for access to the middle. Marker - a special signal that wraps around the ring. The station that won the marker can transmit its data. However, FDDI may have low principal powers in Token Ring, so it can work with a larger Swiss protocol. For example, the modulation algorithm has been changed physically. Token Ring uses the Manchester coding scheme, which influences the sub-signal of the signal, which is transmitted whenever the data is transmitted. In FDDI implementations, the "five out of two" coding algorithm is 4V/5V, which ensures the transmission of four information bits and five bits that are transmitted. When transmitting 100 Mb/s of information per second, 125 Mb/s is physically transmitted in the measure, instead of 200 Mb/s, which would have been necessary when using Manchester coding. Optimized that core access control (Medium Access Control - VAC). In Token Ring it is based on a bit-by-bit basis, and in FDDI on a parallel processing of a group of four or eight bits that are transmitted. Tse lowering the power to the code of possession. Physically, the FDDI ring is made up of a fiber-optic cable made of two light-conducting fibers. One of them is established by the primary ring (primary ring), the main one is victorious for the circulation of markers in data. Another fiber is satisfied with the second ring (secondary ring), є reserve and normal mode is not broken. Stations connected to FDDI are divided into two categories. Class A stations can be physically connected to the primary and secondary circuits (Dual Attached Station - a dual-connected station); 2. Class B stations can only be connected to the primary circuit (Single Attached Station - a one-time connected station) and are connected only through special extensions, which are called concentrators. Ports of framing outbuildings that are connected to FDDI tiers are classified into 4 categories: A port, port, M port and S port. Port A is the port that receives data from the primary port and transfers it from the port. A port is a port that receives data from the secondary ring and transfers it from the primary ring. M (Master) and S (Slave) ports transmit and receive data in one and the same ring. The M-port is switched on the hub for connecting the Single Attached Station via the S-port. Standard X3T9.5 can be low. Zagalna dozhina podvіynogo fiber-optic ring - up to 100 km. Up to 500 class A stations can be connected to the ring. Between nodes with a wide-range fiber-optic cable - up to 2 km, and with a wide-range single-mode cable, the main parameters of the fiber are that of the receiving-transmitting power (can reach 60 and more km). Topology Zastosovuvani when prompted by LOM flow control mechanisms are topologically fallow, which makes it impossible to change Ethernet IEEE 802.x, FDDI ANSI, Token Ring IEEE 802.6 and others in the middle of a single medium of expansion. Irrespective of the fact that Fiber Channel can sing the same world to us, this flow control mechanism does not in any way interfere with the topology of the middle of the universe and is based on the same other principles. Kozhza n_port at pidklichenni to ґrat fibre channel pass through the register (log-in) і ilforms about the addresses Prostir unusual universities, at the pirstavi of the same one, it is clear. . Since Fiber Channel's flow control mechanisms are the prerogative of the lattice itself, then it is not important for the node, as the topology lies in its basis. Point-to-point The simplest scheme, based on the last full-duplex connection of two N_ports with mutually acceptable parameters of the physical connection and the same service classes. One of the hubs takes address 0, and the other one - 1. In fact, such a scheme can be seen as an example of a circular topology, since there is no need for interfacing access to arbitration. As a typical example of such a connection, it is possible to make the most common connection between a server and an existing RAID array. Loop with arbitrage access A classic connection scheme for up to 126 ports, from which everything began, as judged by the abbreviations FC-AL. Whether two ports in the country can exchange money for the help of a full-duplex connection, just like a point-to-point type. In this case, the role of passive repeating signals equal to FC-1 with minimal clutter, which, perhaps, is one of the main advantages of FC-AL technology over SSA. On the right, in the fact that addressing in SSA is induced on a known number of intermediate ports between the owner of that controller, the address header of the SSA frame should be hop count. The skin port, which is zestrichaetsya on the frame frame, changes instead of the first lichnik to one and then regenerates the CRC, thereby significantly reducing the delay in transmission between ports. In order to unique this unimportant effect, the FC-AL retailers gave priority to absolute addressing, which, as a result, allowed the frame to be retransmitted with a fixed look and with minimal latency. The word ARB, which is transmitted by the method of arbitration, is not understood and not defeated by the outstanding N_ports, therefore, with such a topology, the node's power additions are designated as NL_port. The main advantage of the loop with arbitrage access is the low co-operation between the number of connected outbuildings, which is why it is most likely to be won for combining a large number of hard disks with a disk controller. It's a pity, let's go to the NL_port, or a happy cable, open a loop and break it in a non-practical way, through which, in a clean look, such a scheme is no longer vvazhaetsya per ...

FDDI technology is rich in why it is based on Token Ring technology, developing those fundamental ideas. The distributors of FDDI technology set themselves the following priorities:

Increase bit rate of transmission up to 100 Mb/s.

Increase stability to higher levels for the standard procedures of installation after different types - cable failure, incorrect operation of the node, concentrator, faulty high line switching to lines, etc.

It is most efficient to win the potential throughput of the building of both asynchronous and synchronous traffic.

The FDDI network will be based on two fiber-optic links, which will establish the main and backup routes for data transmission between the nodes of the network. Vicoristannya dvoh kіlets - tse main way to increase the stability to vіdmov at the edge of FDDI, and the universities, if you want to reach them, must be connected to both kіltsy. In the normal mode, the data is allowed to pass through all the nodes and all the stations of the primary cable (Primary) circuit, which is called the Thru mode - "through" or "transit". The second ring (Secondary) does not win in this mode.

At times, be of any mind, if a part of the primary ring cannot transmit data (for example, by shaving the cable or the top of the knot), the primary ring unites with the secondary one (Fig. 31), reclaiming the unity of the ring. This mode of robotic mesh is called Wrap, so it's "swallowing" or "swallowing" a ring. Swallowing operation is controlled by concentrators and/or FDDI adapters. To simplify the procedure, the data of the primary ring are always transmitted against the year's arrow, and according to the second one - the year's. Therefore, with the establishment of a closed circle of two stations, the transmitting stations, like before, are connected to the receivers of the land stations, which allows the correct transmission and reception of information by the land stations.

The FDDI standards have a lot of respect for different procedures, which allow you to designate the presence of the operator in the enterprise, and that the necessary reconfiguration is required. Merezha FDDI can again reaffirm its practice in several different types of elements. When there are many merezhas, they break up into sprats that do not tie merezhas.

Mal. 31. Reconfiguration of the FDDI cell in different video

Rings in FDDI networks are considered as an important medium for data transfer, which is divided, and a special access method is assigned to it. This method is closer to the Token Ring access method and is called the marker (or token) ring method - token ring (Fig. 32, a).

The station can transmit its own data frames only in that case, as it took a special frame from the front station - an access token (Fig. 32, b). After all, you can transfer your frames, like a stink, for an hour, called the hour of the morning of the token - Token Holding Time (THT). After the end of the THT hour, the station can complete the transfer of its own frame and pass the access token to the next station. Well, at the moment of receiving the token of the station there are no frames for transmission in the future, then it will not broadcast the token of the attacking station. At the FDDI border, the skin station has an upstream neighbor and a downstream neighbor, which are indicated by physical links and direct transmission.

The skin station in the measure constantly receives the frames transferred by the forward court and analyzes the received address. Since the address of recognition is not known from її vlasnoy, it broadcasts the frame to its advancing susіdovі (Fig. 32, c). It is necessary to indicate that, if the station has hoarded a token and is transmitting its own power frames, then for a long period of time it will not broadcast frames that will come, but will see them.

If the frame addresses are changed to the address of the station, then it copies the frame to its internal buffer, checks its correctness (mainly, for the checksum), passes the data field for further processing to the protocol, which should lie higher than FDDI (for example, IP), and then we transmit the exit frame to the border of the advancing station (Fig. 32, d). For a frame that is transmitted in a measure, the station recognizes three signs: recognizing the address, copying the frame and the daytime or presence in a new pardon.

The next frame continues to rise in price with a mesh, translucent with a skin knot. The station, which is a frame for the frame, is viable for those who saw the frame from the frame, after that, like a wine, having made a new turn, I went back to it (Fig. 32, e). When you leave the station, you check the signs on the frame, what happens to the station is recognized and when you don’t get it. The process of updating information frames is not included until the binding to the FDDI protocol, but the protocols of other equals can be taken care of.

Mal. 32. Frame processing by FDDI ring stations

The structure of the protocols in the FDDI technology in the parallel with the seven-layer OSI model is pointed at the little 33. FDDI implements a physical layer protocol and a protocol for driving media access (MAC) of the link layer. Like a lot of other technologies of local networks, FDDI technology uses protocol 802.2 for Data Link Control (LLC), conforms to IEEE 802.2 and ISO 8802.2 standards. FDDI wins the first type of LLC procedures, when nodes are used in datagram mode - without inserting a call and without redoing the use of scrambled frames.

Mal. 33. Protocol structure in FDDI technology

The physical line of division into two drives: the independent medium drive PHY (Physical), and the fallow media drive PMD (Physical Media Dependent). The work of all equal control protocol is carried out by the SMT (Station Management) station.

Riven PMD ensures the necessary data transmission from one station to another via fiber optic. Yoga specifics are:

Optical signal tightness and high-mode fiber optic cable 62.5/125 µm.

Wimogi to optical bypass switches and optical bypass switches.

Parameters of optical connectors MIC (Media Interface Connector), їх marking.

Dovzhina hvili 1300 nanometers, for which practice they are accepted.

Signaling in optical fibers is similar to the NRZI method.

The specification of TP-PMD indicates the possibility of data transfer between torsion pair stations in accordance with the MLT-3 method. The specifications for PMD and TP-PMD have already been reviewed by branches dedicated to Fast Ethernet technology.

The PHY peer encodes and decodes the data that circulates between the MAC peer and the PMD peer, as well as ensures the clocking of information signals. Yoga specifics are:

coding information is consistent up to scheme 4B/5B;

signal timing rules;

help up to the stability of the clock frequency of 125 MHz;

rules for converting information from a parallel form to the last one.

The MAC fee is responsible for maintaining access to the media, as well as for receiving and processing data frames. The new one has the following parameters:

Token transfer protocol.

Rules for hoarding and relaying the token.

Frame molding.

Rules for generating and recognizing an address.

Rules for calculating and rechecking a 32-bit checksum.

The SMT layer overrides all management functions and monitoring of all other layers of the FDDI protocol stack. In the management of the ring, I take the part of the FDDI skin vuzol. Therefore, all universities are exchanged with special SMT frames for managing the network. The SMT specification has the following:

Algorithms for Revealing Pardons and Remembrance after Breaks.

Rules for monitoring the work of the ring and stations.

Management of the ring.

Procedures for the initialization of the ring.

The security of the FDDI barrier is ensured for the control of the SMT line by other lines: for the help of the PHY line, the lines are used for physical reasons, for example, through cable shearing, and for the additional MAC line - the logical lines of the line , for example, spending the necessary internal way to transfer the token and data frames between hub ports

The next table shows the results of matching FDDI technology with Ethernet and Token Ring technologies.

Characteristic		ethernet	token ring
Bitova swidkist
Topology	Podviyne kіltse trees	Tire/Zirka	Zirka/kiltse
access method	Part of the turnover of the token		Priority reservation system
Transmission center	Bagatomodov fiber, unscreened twisted pair	Thin coax, thin coax, twisted pair, optical fiber	Screened and unscreened twisted pair, optical fiber
Maximum length of the fence (without bridges)	200 km (100 km on the ring)
Maximum distance between nodes	2 km (-11 dB between nodes)
Maximum number of knots	500 (1000 CZD)		260 for screened bets, 72 for non-screened bets
Taktuvannya and revival after vіdmov	The implementation of the timing and the renewal of the follow-up	Not assigned	Active monitor

FDDI (Fiber Distributed Data Interface) is the same standard, chi, virnish, a set of merging standards, orienting, transmitting, transmitting data over fiber optic wireless with a speed of 100 Mb/s. An important part of the specification for the FDDI standard was broken up by the XZT9.5 (ANSI) problem group in the other half of the 80s. FDDI has become the powerhouse of the STOCK, which is the medium of transmission for optical fiber.

In this hour, most of the mesh technologies support the fiber optic interface as one of the options for the physical level, but FDDI is overrun by the most widely used high-width technology, the standards for yak have been re-verified by the hour and have settled down, and the possession of different varieties shows the garniy steps of the mind.

When developing FDDI technology, the following methods were put as the most priority:
- Increased bit rate of data transmission up to 100 Mb/s;
- Improvement of the capacity of the truss for the calculation of standard procedures for the installation of the following types of different genus - poor cable, incorrect work of the truss knot, viniknennya of the high level of switching to the line too thin;
— Maximally efficient use of potential throughput capacity for both asynchronous and synchronous graphics.

FDDI technology is rich in why it is based on Token Ring technology, developing those fundamental ideas. The FDDI protocol has the same validity as Token Ring. Values of power of connection with vimogami, yakі nebhіdnі for pіdtrimki great swidkostі transfers of information, great vіdstany and possibility of order for asynchronous transmission of data to conduct synchronous transmission. Two main features in token control protocols for FDDI and IEEE 802.5 Token Ring:
- at Token Ring station, as it transmits frames, removes the dotty marker, the docks do not remove all forwarded packets. In FDDI, the station issues a token immediately after the end of the transmission of the frame (frames);
— FDDI does not prioritize that reserve field, like Token Ring win for viewing system resources.

At the table 6.1. the main characteristics of the FDDI measure are shown.

Table 6.1. Main characteristics of the FDDI measure

Transmission speed
Media access type	markernium
Maximum frame size data
Maximum number of stations
Maximum distance between stations	2 km (bagatomode fiber) 20 km* (single-mode fiber) 100 m (UTP Cat.5 twisted pair) 100 m (screened twisted pair IBM Type 1)
The maximum length of the road bypassing the marker	200 km
The maximum length of the fence with a circular topology (perimeter)	100 km** (under the FDDI ring)
	Optical fiber (multi-mode, single-mode), twisted-pair (UTP Cat.5, IBM Type 1)

* Deyakі robniki let's get the right to the v_dstan transfers up to 50 km.
** If the length of the line is set, then it is correct to save the balance in the event of the appearance of a single opening of the line, or if one of the stations of the line is switched on (WRAP mode) - with this line, the bypass of the marker is not overridden 200 km.

Principle dії

The classic version of the FDDI line will be based on two fiber-optic rings (hanging ring), the light signal is thus expanded in the opposite lines, Fig. 6.1 a. The leather vuzol is connected to the reception and transmission to both kіltsіv. The very same kіltseva physical topology implements the main way to increase the strength to the vіdmovi merezhi. In the normal mode, the robots are given to go from the station to the station only one by one, as it is called the primary (primary). In order to signify directly the flow of data from the primary kіltsi, an anti-year arrow is given. The transmission route reflects the logical topology of the FDDI network, as a rule, the ring. All stations, transmitting and receiving, will rebroadcast data and receive it in the same way. The secondary ring (secondary) is a backup and in normal mode, the robots for data transmission are not victorious, although in a new way, there is an uninterrupted control over the ring's integrity.

Mal. 6.1. FDDI control loop: a) normal operation mode; b) curled ring mode (WRAP)

In times of guilt, be it in the measure, if part of the primary ring is not able to transmit data (for example, shaving the cable, out of tune, or switching on one of the nodes), for data transmission, the second ring is activated, as if adding the primary , reclaiming the same logical transmission ring, fig. 6.1 b. This mode of operation of the fence is called WRAP, so that the “switching” of the ring is carried out. The operation of the throat is carried out by two wired outbuildings, which are on the side of the wrong side of the fault (the wired cable, or the station / hub, which went out of tune). Itself through qі pristroї vіdbuvaєtsya ob'єdnannya primary and secondary cell. In this way, the FDDI merger can again prove its practicality and integrity in different single species of elements. In the event of a failure of the link, it automatically switches to the normal mode of operation with the transfer of data only to the primary ring.

The FDDI standard attaches great importance to various procedures, which allow the separate repair mechanism to detect the presence of a malfunction in 5 measures, and then perform the necessary reconfiguration. When there are multiple lines, the line breaks up into sprats that do not tie the line - microsegmentation of the line occurs.

The work of the FDDI measure runs on a deterministic marker access to a logical loop. In the beginning, the initialization of the ring is sent, in the process of ringing one of the stations, a special shortening package of service data is issued - a marker (token). After the marker has become circulating around the ring, stations can exchange information.

Docks do not transfer data from station to station, circulating only a marker, fig. 6.2 a, with the withdrawal of such a station may be able to transmit information. At the FDDI border, the skin station has an upstream neighbor and a downstream neighbor, which are indicated by physical links and direct transmission. In the classic version, it is designated as the first ring. The transfer of information is organized as packets of data up to 4500 bytes, called frames. If at the moment the marker is taken away, the station does not have data to transmit, then having taken the marker away, it will broadcast it negligently farther along the ring. For the purpose of transmitting, the station, having removed the token, can reduce it and conduct a regular transmission of frames for an hour, which is called the hour of the TNT marker (token holding time) (Fig. 6.2 b). After the end of the TNT hour, the station can complete the transmission of its own frame and transmit (admit) the marker of the attacking station, fig. 6.2 Art. If there was a time to transmit information, there could be only one station, but the same one, as if the marker was hooted.

Mal. 6.2. Transfer of data

The skin station of the border reads the address fields of the rimmed frames. In that case, if the address of the station - MAC addresses - is in the address field of the master, the station simply relays the frame along the ring, fig. 6.2 p. How is it possible that the address of the station is stored with the address field of the owner in the frame, the station copies its internal data buffer to its frame, checks its correctness (for the checksum), transfers the data field for further processing to the protocol of the highest level (for example, IP) and then transmit the exit frame of the border of the offensive station (Fig. 6.2 e), putting three characters in front in the special fields of the frame: recognizing the address, copying the frame and the presence or presence in the new pardon.

They gave frames, broadcasting from the station to the station, turning to the exit station, which was their dzherelom. The station-dzherelo for the skin frame re-verifies the signs of the frame, the number of signs to the station is recognized and there are no signs of damage, and everything is fine, closing the frame (Fig. 6.2 e), changing the resources of the frame, otherwise, in a different case, the health clarification I will repeat transmission. For some reason, the function of the remote frame is assigned to the station, as if it were a dzherel.

Marker access is one of the most effective solutions. For some reason, the real productivity of FDDI circles, with a great engagement, reaches 95%. For example, the productivity of an Ethernet network (near the borders of a colloquial domain) is 30% of the throughput capacity.

The format of the marker and the FDDI frame, the procedure for initialization of the ring, as well as the supply of resources for the distribution of resources in the normal mode of data transmission are discussed in clause 6.7.

Warehouses are equal to the FDDI standard and the main functions that are related to them are shown in fig. 6.3.

Like a lot of other local network technologies, FDDI technology wins protocol 802.2 data link control (LLC), functions in IEEE 802.2 standards, and ISO 8802.2, FDDI wins first type of LLC procedures, with which nodes work in a datagram modes - without installation z'edna that without vodnovlennya vtrachenih or poshkodzhenikh cadres.

Mal. 6.3. Warehouse to FDDI standard

More recently (before 1988) the standards were similar (the names of the most recent ANSI/ISO documents for FDDI are listed in Table 6.2):
- PMD (physical medium dependent) - the lower level of the physical level. These specifications vary from the transmission medium (high-mode fiber optic cable) to the optical receivers (attenuation and operating length of 1300 nm are allowed), the maximum allowable distance between stations (2 km), types of roses, functionality optical bypass jumpers. , as well as signaling in optical fibers.
- PHY (physical) - the upper level of the physical level. You can select the encoding scheme and decoding of data between MAC-equal and equal PMD, the synchronization scheme and special key characters. This specification includes: coding of information up to the scheme 4B/5B; signal timing rules; help up to the stability of the clock frequency of 125 MHz; rules for converting information from a parallel form to the last one.
- MAC (media access control) - control of access to the media. The goal is determined by: marker management processes (transmission protocol, rules for storing and retransmitting the marker); shaping, acceptance and processing of data frames (addressing, displaying pardons and renewals based on reverification of a 32-bit checksum); mechanisms for spreading smog between the nodes
- SMT (station management) - control of the station. Tsey special all-season rіven is signing: protocols of mutual rіvnya

Technology FDDI (Fiber Distributed Data Interface) - The fiber optic interface of the distribution of data is the first technology of local networks, in the medium of data transmission is a fiber optic cable. Works with the creation of technologies and attachments for the use of fiber-optic channels in local networks have been launched in 80 years, not without warning after the beginning of industrial operation of similar channels in territorial networks. The XZT9.5 problem group was researched by ANSI from 1986 to 1988. the original version of the FDDI standard, which ensures the transmission of frames with a speed of 100Mb/s of a floating fiber-optic ring with a length of up to 100km.

Main characteristics of technology

FDDI technology is rich in why it is based on Token Ring technology, developing those fundamental ideas. The distributors of FDDI technology set themselves the following priorities:

increase the bit rate of transmission up to 100Mb/s;

increase the capacity of the wire for the calculation of standard procedures for the installation of a different type of cable, incorrect operation of the node, concentrator, high line shift on the line too thin;

to maximize the efficiency of the capacity building capacity of both asynchronous and synchronous (sensitive to obstruction) graphics.

The FDDI network will be based on two fiber-optic links, which will establish the main and backup data transmission paths between the nodes of the network. kіltsy.

In the normal mode, the data to pass through all the nodes and all the cables to the cable is less than the primary (Primary) circuit, which mode names the mode Thru-"Skrіznim" chi "transit". The second ring (Secondary) does not win in this mode.

At times, be of any mind, if a part of the primary ring cannot transmit data (for example, shaving the cable or the top of the knot), the primary ring unites with the secondary one (Fig. 9.8), re-establishing a single ring. The whole mode of robots is called Wrap, tobto "gortannya" or "gortannya" kіlets. The laryngeal operation is carried out by concentrators and/or FDDI adapters. - at the gate (pictured behind the year's arrow). Therefore, with the establishment of a closed circle of two stations, the transmitting stations, like before, are connected to the receivers of the land stations, which allows the correct transmission and reception of information by the land stations.

The FDDI standards have a lot of respect given to different procedures, which allow you to determine the presence of the change in the measure, and then to generate the necessary reconfiguration. Merezha FDDI can again reaffirm its practice in several different types of elements. The FDDI technology supplements the mechanisms of detection of Token Ring technology with the mechanisms of reconfiguration of the transmission path in the link, based on the presence of redundant links, which are secured by another ring.

Fig.9. 8 Reconfiguration of the FDDI ring in different drivers

Rings in FDDI networks are considered as an important medium for data transfer, which is divided, and a special access method is assigned to it. This method, which is close to the Token Ring access method, is also called the token ring method.

The permissions of the access method depend on the fact that the hour of token deletion in the FDDI pool is not a constant value, as it is in the Token Ring pool. the access method is limited to asynchronous graphics, which is not critical to small delays in the transmission of frames. For a synchronous chart, the marker's hour, like before, is filled with a fixed value.

MAC addresses can be in the IEEE 802 technology standard format.

On fig. 9.9 the consistency of the protocol structure in the FDDI technology of the OSI seven-layer model has been established. FDDI defines a protocol for physical alignment and a protocol for driving media access (MAC) to a channel. Like in many other technologies of local merging, FDDI technology wins over the data link control protocol LLC, which is similar to the IEEE 802.2 standard. In this way, regardless of the fact that FDDI technology was developed and standardized by ANSI, and not by the IEEE committee, it will again fit into the structure of the 802 standards.

Fig.9. 9 Protocol structure in FDDI technology

The main feature of FDDI technology is the cost of station maintenance. Station Management (SMT) , The SMT layer itself takes care of all the functions of managing and monitoring the solution of all the layers of the FDDI protocol stack. In the management of the ring, I take the part of the FDDI skin vuzol. Therefore, all universities are exchanged with special SMT frames to manage the network.

The security of the FDDI measure is secured by the protocols of those other equals: for the additional physical equal, the additional measures are used due to physical reasons, for example, through the cable shedding, a different internal path for transferring the token and data frames between the ports of the concentrator .

10.2. FDDI technology

Technology FDDI (Fiber Distributed Data Interface) - fiber optic interface of the distribution of data - the first technology of local networks, at the same transmission medium there is a fiber optic cable. Works with the creation of technologies and attachments for victorious fiber-optic channels at local barriers began to grow in 80 years, not without delay after the beginning of industrial exploitation of similar channels at territorial barriers. Before the retailers, there was a task: to expand the standard of the local network, based on the fiber optic cable, which would ensure the security of 100 Mbit/s and could reach a length of up to 100 km.
^

Main characteristics of technology

FDDI technology is rich in why it is based on Token Ring technology, developing those fundamental ideas. The retailers of FDDI technology set themselves the most priority offensive tsіlі:

increase the bit rate of transmission up to 100 Mb/s;
increase stability up to the level of wires for the account of standard procedures for installation after the change of type - poor cable, incorrect operation of the node, concentrator, faulty high line switching to the line too thin;
maximize the efficiency of the potential throughput of the building of both asynchronous and synchronous (sensitive to clutter) traffic.

The FDDI network will be based on two fiber-optic links, which will establish the main and backup routes for data transmission between the nodes of the network. The presence of two circles is the main way to increase stability to the FDDI borders, and the universities, if they want to speed up the promotion of the potential of reliability, are due to the connection to both circles.

In the normal mode, the data to pass through all the nodes and all the cables to the cable is less than the primary (Primary) circuit, which mode names the mode Thru- "we will open" chi "transit". The second ring (Secondary) does not win in this mode.

At times, be of any mind, if a part of the primary ring cannot transmit data (for example, by shaving the cable or the top of the knot), the primary ring unites with the secondary one (Fig. 76), reclaiming the single ring. The whole mode of robots is called Wrap, tobto "gortannya" or "gortannya" kіlets. Swallowing operation is controlled by concentrators and/or FDDI adapters. To simplify the procedure, data on the primary ring are always transmitted in one direct way (on the diagrams, which are directly shown against the year's arrow), and on the secondary - at the back (shown behind the year's arrow). Therefore, with the establishment of a closed circle of two stations, the transmitting stations, like before, are connected to the receivers of the land stations, which allows the correct transmission and reception of information by the land stations.

Mal. 76. Reconfiguration of the FDDI cell in different drivers

In FDDI standards, a lot of respect is given to different procedures, which allow you to define the presence of the operator in the system, and that the necessary reconfiguration is required. Merezha FDDI can again reaffirm its practice in several different types of elements. When there are many merezhas, they break up into sprats that do not tie merezhas.

Rings in FDDI networks are considered as an important medium for data transfer, which is divided, and a special access method is assigned to it. This access method is similar to the Token Ring access method and is called the token ring method.

The importance of the access method depends on the fact that the time of token deletion in the FDDI pool is not a constant value, as it is in the Token Ring pool. This time to lie down in the face of the zavantage of the ring - with a small zavantazhennya, it will increase, and with great zavantazhennya, it can change to zero. Changes in the access method cost more than asynchronous traffic, which is not critical to a small delay in the transmission of frames. For synchronous traffic, the marker's hour, like before, is filled with a fixed value. Frame priority mechanism, similar to that adopted in Token Ring technology, in FDDI technology every day. The distributors of the technology were wrong, that they divided the traffic into 8 equal priorities over the world and it was sufficient to divide the traffic into two classes - asynchronous and synchronous, the rest of them are serviced on a regular basis, navit when switching the cycles.

In other cases, the transfer of personnel between the stations of the ring on the MAC level relies on Token Ring technology. Stations FDDI zastosovuyut algorithm early token, as a measure Token Ring with a speed of 16 Mbit / s.

MAC addresses can be in the IEEE 802 technology standard format. The FDDI frame format is close to the Token Ring frame format; Signs of recognizing the address, copying the frame and pardon allow you to save in Token Ring the procedures for processing frames in the control station, intermediate stations and control station.

^ On fig. 77 shows the structure of the protocols in the FDDI technology of the seven-layer OSI model. FDDI implements a physical layer protocol and a protocol for driving media access (MAC) of the link layer. Like in many other technologies of local merging, FDDI technology wins over the LLC data link control protocol, which is similar to the IEEE 802.2 standard. In this way, regardless of the fact that FDDI technology was developed and standardized by ANSI, and not by the IEEE committee, it will again fit into the structure of the 802 standards.

Mal. 77. Protocol structure in FDDI technology

The main feature of FDDI technology is the cost of station maintenance. Station Management (SMT). The SMT layer itself takes care of all the functions of managing and monitoring the solution of all the layers of the FDDI protocol stack. In the management of the ring, I take the part of the FDDI skin vuzol. Therefore, all universities are exchanged with special SMT frames for managing the network.

Vіdmovostіykіstі merezh FDDI zabezpechuєtsya protocols іnshih іvnіv: for the help of a physical equal, the measures of physical reasons are used, for example, through a cable shed, and for the additional level of MAC - logical measures, for example, the input of the necessary internal way to transfer the marker and data frames between the ports of the concentrator.
^

Features of the FDDI access method

For the transmission of synchronous frames, the station may have the right to request a marker for the hour of the due date. At which time the marker can be removed, a fixed value is given.

If the FDDI ring station needs to transmit an asynchronous frame (the type of the frame is determined by the protocols of the upper levels), then the possibility of hoarding the marker when doing yoga The required station can be set to an hour interval, which is past the moment of the marker's early arrival. This interval is called token rotation time (TRT). The TRT interval is equal to the other value - the maximum allowable hour for the turnover of the marker on the ring T_0rg. As for the Token Ring technology, the maximum allowable hour for a token turnover is a fixed value (2.6 for the opening of 260 stations in the ring), then the FDDI technology of the station is based on the value of T_0rg pid hour of the initialization of the ring. The skin station can propagate its own T_0r value, as a result, for the ring, the minimum of the hours proponated by the stations is set. Tse allows you to protect the programs that are used at the stations. Call synchronous programs (additions of the real time) more often to transfer data in small portions, and asynchronous programs should more quickly deprive access to less, but in larger portions. Transmission is hoped for by stations that transmit synchronous traffic.

In this way, when the transfer marker is needed for an asynchronous frame, the actual hour of the turnover of the TRT marker is equal to the maximum possible T_0r. If the ring is not overwhelmed, then the marker arrives earlier, the interval T_0r will end later, then TRT< Т_0рг. В этом случае станции разрешается захватить маркер и передать свой кадр (или кадры) в кольцо. Время удержания маркера ТНТ равно разности T_0pr - TRT, и в течение этого времени станция передает в кольцо столько асинхронных кадров, сколько успеет.

If the ring is overwhelmed and the marker is delayed, then the TRT interval will be larger than T_0r. And here the station does not have the right to request a marker for an asynchronous frame. If all the stations in the measure want to transmit only asynchronous frames, and the marker ending the wrapper on the ring too late is correct, then all stations will skip the marker in the repeat mode, the marker will not be able to quickly turn the turn on the next cycle, but the stations may still have the right to request the marker before take your shots.

The FDDI access method for asynchronous traffic is adaptive and well-adjusted to time traffic.
^

Visibility of FDDI technology

To ensure the water resistance of the FDDI standard, two fiber optic rings were added - the primary and the secondary. The FDDI standard allows two types of connection of stations to the border. One-hour connection to the primary and secondary connections are called sub-connections - Dual Attachment, DA. Connections only up to the primary ring are called single connections - Single Attachment, SA.

^ In the FDDI standard, the presence was transferred to a number of terminal nodes - stations (Station), as well as concentrators (Concentrator). For stations and concentrators, it is acceptable whether there is any type of connection to the border - both single and sub-connected. Such attachments may be named: SAS (Single Attachment Station), DAS (Dual Attachment Station), SAC (Single Attachment Concentrator) and DAC (Dual Attachment Concentrator).

^ Ring the hubs to be connected, and the stations are single, as shown in Mal. 78, hotch tse i not obov'yazkovo. To make it easier to attach it correctly to the border, they are marked with roses. Roses of type A and B are to blame for attachments with sub-wiring, roses M (Master) - for a hub for a single connection of a station, for roses for a wired connection, mother type S (Slave) is to blame.

Mal. 78. Connecting the hubs up to FDDI heels

In case of disposable cable shearing between attachments with FDDI subwire connections, it is possible to continue normal operation for automatic reconfiguration of internal paths in frame transfer between ports of the concentrator (Fig. 79). Two-time shearing of the cable was made up to the adoption of two insulated FDDI sheaths. When shaving the cable, which goes to the station with a single connection, it becomes torn in the middle, and the ring continues to reconfigure the inner path in the concentrator - port M, which was connected to the given station , you will be turned off from the wild way.

Mal. 79. Reconfiguration of the FDDI measure for the hour of shaving

In order to save the cost of service when the power is switched on in stations with sub-wires, so that the DAS stations, the remaining ones, are equipped with optical bypass switches (Optical Bypass Switch), which create a bypass path of light streams when there is a livelihood, like stench from the station.

You can connect up to two ports of one or two hubs, DAS stations or DAC hubs, creating a tree-like structure with main and backup links. For locking, the port supports the main call, and port A is the backup. Such a configuration is called a Dual Homing connection.

Vidmovostіykіst podtremuєєє for rahunі stіyny stієnіn іnіnі іzhnі іnі sіdnіmi SMT concentrators і і stations іn hourly intervals ії circulation ії marker і kadіrі, аnd also for the presence of physical z'іdnannya mіzh sіdnіnіmi mіzh sіdnіmi ports і mеrіzhі. There is no visible active monitor at the FDDI measure - all stations and concentrators are equal, and in case of detected air pollution, they start the process of re-initialization of the measure, and then reconfiguration.

Reconfiguration of internal paths at concentrators and tether adapters is equipped with special optical jumpers, so that they can redirect the light prompt and can achieve a folding structure.
^

Physical level of FDDI technology

In the FDDI technology for transmitting light signals over optical fibers, 4V/5V logical coding is implemented for the same NRZI physical coding. The circuit should be designed before transmission over the line of communication of signals with a clock frequency of 125 MHz.

Since out of 32 combinations of 5-bit symbols, only 16 combinations are needed to encode out of 4-bit symbols, then out of 16, which are left out, a few codes are selected, so they are victorious as services. The most important service symbols are preceded by the Idle symbol - a simple one, which is constantly transmitted between ports with pauses between data frame transmissions. For the work of this station and the concentrators of the FDDI network, they can store permanent information about the camp of the physical facilities of their ports. At the time of the stream of Idle symbols, the physical link is fixed and the reconfiguration of the internal path of the concentrator or station is enabled, as it is possible.

^ When connecting the two nodes with a cable, the port will break the procedure for establishing a physical connection. In this procedure, the succession of service symbols to the code 4B / 5B is won, for the help of which a deak of physical commands is created. These commands allow ports to be assigned one in one port type (A, B, M or S) and vice versa, which is correct (for example, S-S is incorrect, etc.). In order to make sure that the data is correct, we give a test of the channel strength when transmitting symbols in 4V / 5V codes, and then we check the validity of the MAC level of the devices in the way of transmitting MAC frame decimals. If all the tests were successful, then the physical condition is respected as established. The robot of the installation of a physical control protocol for the control of the SMT station.

The physical ratio of division into two sub-drives: the independent medium sub-drive PHY (Physical) and the PMD (Physical Media Dependent) sub-drive, which is to be deposited in the media (div. Fig. 77).

FDDI technology currently introduces two PMD drives: for fiber optic cable and for non-screened twisting bets of category 5. The remaining standard, which appears later than optical, is called TP-PMD.

PMD fiber optic transmission ensures the necessary data transmission from one station to another via optical fiber. Yoga specification is:

vikoristannya as the main physical core of the bugatomode fiber-optic cable 62.5/125 microns;
to the extent of optical signal tightness and maximum extinction between the nodes of the mesh. For a standard multi-mode cable, it can be brought up to a boundary distance between nodes of 2 km, and for a single-mode cable, it can be increased to 10-40 km, depending on the quality of the cable;
help to optical bypass switches and optical bypass switches;
parameters of optical sockets MIC (Media Interface Connector), їх marking;
vikoristannya for the transmission of light with long wind 1300 nm;
signaling in optical fibers is similar to the NRZI method.

The TP-PMD allowance indicates the possibility of transmitting data between stations over torsion pairs up to the MLT-3 physical coding method, which has two equal potentials: +V і -V for the presentation of data on the cable. To remove the equal intensity of the spectrum, the data signal must pass through a scrambler before physical encoding. The maximum distance between nodes is up to TP-PMD standard up to 100 m-code.

The maximum distance of the FDDI circuit will be 100 kilometers, the maximum number of stations with sub-connections at the circuit will be 500.
^

Pairing FDDI with Ethernet and Token Ring technologies

At the table 3.7 shows the results of matching FDDI technology with Ethernet and Token Ring technologies.

Table 3.7. Characteristics of FDDI, Ethernet, Token Ring technologies

The FDDI technology was developed for stosuvannya at large yards of merezha - on the main lines between large merezha, for example, budivel merezha, as well as for connection to the merezha of highly productive servers. Therefore, the main ones for retailers were to ensure the high speed of data transfer, the stability to the level of the protocol and the great distance between the knots of the merezh. All the goals were within reach. As a result, FDDI technology turned out to be more expensive, if not expensive. The emergence of a cheaper option for twisted betting has not cheaply reduced the connection rate of one university to FDDI. Practice has shown that the main area of application of FDDI technology has become the highways, which are formed from many lives, as well as the scale of the great city, tobto the MAN class. For the connection of client computers and the launch of small servers, the technology proved to be too expensive. Oskіlki obladnannya FDDI vypuskaєtsya already close to 10 years, a significant reduction of yogo varnostі ochіkuvat not be brought.

.
^ Merez technology ARCNet
When connected to ARCNet add-on topology "bus" or "star". ARCNet adapters support the Token Bus access method (token bus) and provide a performance of 2.5 Mb/s. This method transfers the following rules:

All attachments, connected to the border, can transmit data, having less than allowed to transmit (marker);

at some point in the hour there is only one station in the city, it may be right;

a frame that is transmitted by one station is simultaneously analyzed by all other stations of the line.

In ARCNet networks, an asynchronous transmission method is used (in Ethernet and Token Ring - a synchronous method), i.e., the transfer of a skin byte for them is performed by the ISU (Information Symbol Unit - one transmission), which consists of three service start / stop bits and eight bits danich.

^ In ARCNet, 5 types of frames are assigned (Fig. 80), the numbers indicate the number of fields of frames in bytes.):

ITT frame (Invitations To Transmit) - requested before transmission. Tsya parcel is transferred from one node to another. The station that received such a frame retains the right to transmit data;

FBE frame (Free Buffer Enquiries) - ask about readiness before receiving data. The readiness of the university to receive data is being checked in the frame;

DATA frame - a data packet is transmitted with this help;

ACK frame (ACKnowledgments) - confirmation of acceptance. Confirmation of readiness to receive data (confirmation on PBE) or confirmation of the received DATA frame without glasses (confirmation on DATA);

NAK frame (Negative ACKnowledgements) - not ready to receive. The unavailability of the node to receive data (advance to RVE) or to receive a frame with a pardon (advance to DATA).

Mal. 80. Types of frames for ARCNet merezh
AB (Alert Burst) – cob splitter (wiring the function of the preamble to the frame); EOT (End Of Transmit) - symbol of the end of transmission; DID (Destination Identification) - addresses of the destination (ID-destination). If the field is entered with the value 00h, then the frame is processed by all stations; ENQ (ENQuiry) - a symbol for asking for readiness before receiving data; SOH (Start Of Header) - the symbol of the header; SID (Source Identification) – addresses of the dzherel (ID-dzherel); COUNT = 512-N, de N-packet length, bytes; CRC - checksum; ASK (ACKnowledgments) - a symbol of readiness to receive data; NAK (Negative ACKnowledgements) - a symbol of unavailability before receiving data
All stations in an ARCNet merger are assigned an 8-bit ID (Identification - the physical address of the merging adapter). Tsya addresses are installed by jumpers on the board. The frequency of transmission is determined by the physical addresses of the stations (ID). The first station is the one with the largest address, then the next station is the one with the smallest address, then the next one is the address in order. The skin station knows the address of the next station (NextID or NID). Tsya addresses are determined every hour after the end of the system reconfiguration procedure. After the end of data transmission, the station transfers the right to transmit data to the next station for an additional ITT frame, with which the NID addresses are set in the DID field. The next station is transmitting data, then the ITT frame is thin. In this manner, the skin station hopes to be able to transmit its data.

To send a packet, the station can take a token back. Having removed the marker, the station sends a frame to the FBE station, which may be transmitted data. If the receiving station is not ready, it will send a NAK frame, otherwise - ASK. After otrimavshi ASK, vuzol, like a marker, start transmitting a DATA frame. The hour of acknowledgment of data collection becomes 75.6 µs. As soon as the ACK was canceled, the transmitter transmits the marker of the offensive station. If the NAK is rejected, the sender retransmits the received DATA frame. Then, irrespective of whether it is clear, the marker is transmitted to the next station.

The skin station starts to receive DATA frames, showing the transmission of the AB splitter. Let's change the value of the DID address with our own address. If the addresses are the same, or if a broadcast frame is needed, the data is written to the station's buffer, if not, the frame is ignored. The frame is considered normally accepted, which means it is accepted again and the control sum is set to the value of the CRC field. Having received a normal DATA frame, the station transmits an ACK. If a pardon is issued upon acceptance, then the NAK is passed on. ACK and NAK frames are not sent to a wide DATA frame.

The reconfiguration of the line will be automatically updated every hour when a new station is added to the marker. The middle adapter starts the reconfiguration if the 840 ms pull is not received by the ITT frame. Tse zdіysnyuєtsya by requesting a special reconfiguration frame (Reconfiguration Burst). Such a frame that has been added for any frame, the marker will be ruined (through the collision) and no station in the border is not allowed by the marker (then the right to transfer). After receiving a reconfiguration frame, the skin station is reconfigured to a refresh station for an hour, which is 146x(256-ID) µs. Even after the end of the transmission timeout, there was no timeout (and this is true only for the station with the highest ID address), the host transmits an ITT frame with the DID address, which is better than the main ID. If the station didn’t send it back, the station changes the DID by one and repeats the transfer to the PT frame, etc. If the station is positive, the token is sent to the station, and the ID address is remembered as the address of the next station (NID). This operation is repeated, the dock marker will not turn to the first node (stations with the maximum address). Under the hour of the configuration of the skin station, in the measure, it is recognized that the station will come after it. In this order, a logical ring is formed, which determines the sequence of the transfer of the marker.
^ Technology of virtual merezh
Technology of virtual networks (Virtual LAN) is one of the most important aspects of switching networks, ensuring the transition from the network to the middle of the switching systems. The main purpose of virtual networks is to surround the area of broadband traffic, so that small wideband domains can be organized. Virtual dimensions ensure segmentation with additional creation of logical, dynamic wide domains.

Similar to wide domains based on routers, virtual LOM wide packets and packets with unknown addresses are removed from the extension, so that such packets resemble those of the same domain (virtual domain). There is nothing new here, the same methods are victorious with traditional networks based on concentrators and routers. However, in traditional networks, traffic is widely used in the middle of the concentrator segment and is routed between concentrators. At different virtual networks, frames become wide in the middle of VLANs and are routed between them. In this manner, virtual merezhi are nothing more than a more flexible version of the traditional SCRAP with much greater possibilities.

^ Virtual CLOSE (and connected to it by commutators) can subtrim different types of physical media. At the fences that are commuted, it is possible to operate a centralized resource (highway) with more high speed, low speed of working stations. For example, Ethernet workstations (10 Mbps) can be used as Fast Ethernet, Gigabit Ethernet or ATM servers.

^ The skin port of the switch is responsible for ensuring the support of more than one virtual LOM. It is important to visit in quiet situations, if non-intermediate working stations are connected to the ports of the switch (one station may need to be present at a number of virtual networks). The LOM switches can override the functions of standard routing on the edge level (IP and IPX), such a capability allows organizing data exchange between virtual LOMs without the need to switch external routers.

In efficient implementations of virtual networks, servers can enter up to a number of VLANs. Traffic at this time is not transmitted through the router on the main line, which reduces the traffic on the main line and changes the blockage.

At rich borders, extensions often move from one month to another in the boundaries of the business territory. The administrator of the fence is guilty of the mother's ability to communicate with the attachments, or to coristuvacha with the virtual fences independently of the roztashuvannya. The choice of commutators sounded due to the need to increase the productivity of the measure with an one-hour decrease in the cost of electricity. The organization of virtual scrap is not to blame for reducing the productivity of the company. In virtual LOMs, a wide domain can be connected to extensions, connected to one or more ports of the switch, or connected to ports of different switches. Since VLANs are organized on the basis of logical groups of coristuvachs, then the separation of the stations of the coristuvach cannot be assigned to the management on the basis of routers and concentrators, de groups of coristuvachivs were simply designated as the mass of the separation of the remaining ones.

A wide domain can replace a computer that is in the same place, or place it on a significant page one in one for the support of virtual LOM with multiple WAN channels. Shards for exchange of data in the middle of a group of routers do not change, exchange between stations is richer.

Today you can get a lot of options for implementing VLAN. Simple VLAN options, a set of switch ports, more flexible implementations allow you to create groups based on other criteria. The capacity of the VLAN organization is closely related to the capacity of the switches.

^ Merezhі z urakhuvannyam portsіv.

The simplest option for organizing virtual scrap. VLANs on the basis of ports provide the greatest level of keratinization and security. Attachments communicate with virtual networks based on the ports of the switch, which are physically connected. VLANs on the basis of ports are static and for making changes, it is necessary to physically switch the extensions.

However, on the basis of the ports, virtual merezhi may be singed out. stink easy to install, but allow only one virtual LOM to be trimmed for the skin port. Also, such a solution is not very pleasant with different concentrators or with hard servers, to which there are a lot of coristuvachiv (the server cannot be turned on in different VLANs). In addition, virtual barriers on the basis of ports do not allow making changes to the net with a simple way, shards in the case of skin changes, the need for physical switching of outbuildings.

^ Merezhi based on the MAC address.

If you want to change the type of virtual networks to the simplest ones, VLAN based on the MAC address should be changed more folded, lower on the basis of physical ports. A virtual network based on the MAC address of the group extension, and software, for example AutoTracker, divide the group with a wide domain (VLAN). Merezhy based on the MAC address is one of the most secure and encrypted types of VLAN. To deny access to a virtual network, attachments are responsible for the MAC address, which is used by the AutoTracker program.

Setting up a virtual network based on the MAC address can take up to an hour. In addition, MAC addresses are "tightly wired" in the possession and may need a lot of time to get the address of the outbuildings at the great, territorially divided border. The OmniVision Xylan tier management program allows you to select addresses in the scale of all tiers automatically, allowing the administrator to perform routine work. For the help of these programs, you can set up virtual networks, vikoristovuyuchi zamіst MAC-address associated with them the names of the stations.

^ VLAN on the border line .

The virtual LOM of the tie line allows the administrator to link traffic for that chirch protocol from the virtual tie line. This is how wide-domains are created in networks based on routers. The protocol can be assigned to the IP subdivision form of the IPX tier number. It is possible, for example, to unite at the virtual LOM of all coristuvachiv pdmerezhi, as the bula was organized to the substation of commutators.

The range of possibilities of the switch, for which VLANs will be arranged, determines the flexibility of virtual networks of this type. A lot of virtual scraps of trim line support systems based on decal commutators, but others can only work with one extension.

^ VLAN with protocol support.

This type of virtual mesh will be adjusted according to the protocol specified in the skin frame type. Such a policy allows the administrator to set criteria for which VLANs should be created. The administrator can independently select the fields in the headers of the frames, for which the belonging to the virtual network is assigned, and to make sure that the rules are prepared for all switches of the network. For example, you can put in one virtual dimension of all coristuvachiv, as if working with the NetBios protocol or IP. For work with this type of virtual networks, the administrator is responsible for thoroughly understanding the headings of wide frames.

In addition, as the rules are added to the commutator, the device is installed to the robot with virtual borders based on the rules set by the administrator.

^ Multicast VLAN .

Rich address (multicast) traffic is considered as a broadcast (broadcast), which is transmitted to the whole extent, that unicast (unicast), which provides a point-to-point call. Rich address traffic is a “speck-three speck” exchange (one s bagatma) or bugatochkovy (bagatto z bagatma) and the rest of the hour becomes more and more popular for different merging supplements. A rich address mode can be selected for videoconferencing, exchange systems, novelties and similar systems, where the information itself is transmitted to numerical subscribers.

Virtual SLOTS from rich traffic are created dynamically by eavesdropping IGMP (Internet Group Management Protocol). If you run the program using the multicast mode, you will dynamically join the virtual network, it will be linked to the target program. After the completion of the work with the program, the coristuvach is seen from the virtual network.

Richly addressed traffic in the wild countryside is a stable stream from a wide swarming area. Also, it is better to fix such traffic in one virtual measure to avoid avalanche routing (flooding).

^ Rule based VLAN .

This is the most difficult implementation of VLAN, which allows the administrator to choose any combination of criteria for the creation of virtual LOM. Uvіmknennya pristroїv vіrtualnі LOM it is possible zdіysnіti vsіma pererahovymi more ways for the mind їх іх міхки vіstanovlenymi іn merezі commutators. In addition, as the rules of engagement for all switches, the stench will secure the organization of the VLAN based on the criteria set by the administrator. Shards in such frames are regularly reviewed according to the given criteria, the belonging of coristuvachs to virtual merezhs can be changed in a fallow manner in line with the in-line activity of coristuvachiv.

Virtual LOM based on the rules win a wide range of criteria for belonging to a merezh, including all other options: MAC addresses, merezhny addresses, protocol type, etc. You can also win or choose a combination of criteria for the creation of rules that most accurately match your tasks.

^ VLAN for upgrading coristuvachіv .

VLANs for upgrading coristuvachiv provide a high level of security in the network and hang more suvori to coristuvachiv for access to servers or other merezhnyh resources. For example, a network of upgrades of coristuvachіv can be created for a financial business, and other employees cannot gain access to the ciєї merezhі, without being able to see the new ones. To support such networks at the switches, activate the functions of the firewalls. The administrator can effectively control the access of the corystute by setting the authentication procedure. If you want other options for VLANs to be safe, then only in the measures of up-gradation of koristuvachiv tse vykonuetsya to dosit to a high equal.

Structured cable system

The cable system (SCS) is structured as the main base for the longest hour of the information system. This is the basis for maintaining the functioning of all programs (Fig. 81). Properly designed, installed and administrated cable system lowers the cost of any organization at all phases of your life.

Mal. 81. Row indicators of the middle hour based on the elements of a separate system for processing information
According to statistics, incomplete cable systems are the cause of up to 70% of all downtime in the information system. Irrespective of those that the cable system, as a rule, is more expensive for the majority of other framing components, it is possible to become less than 5% of the total investment in the information merging. In this way, the choice of a structured cable system is already a reconciliation way of investing in the productivity of either an organization or a company.

The cable system is a component of the measure with the most important hour of life, which is better than any other frame of life. The cable system, created on the basis of standards, guarantees the continued functioning of the system and the support of all numerical additions, ensuring the return of investment in the long run of the network.

Hierarchy of the cable system

Structured cable system (Structured Cabling System, SCS) - the price of a set of switching elements (cables, roses, connectors, cross panels and a closet), as well as the technique of їх spilny vikoristannya, as it allows you to create regular structures of junctions, which can be easily expanded in counting measures.

A structured cable system is a kind of "constructor", for the help of which the designer will need some configuration from standard cables, wired with standard sockets and patched on standard cross panels. You can easily change the call configuration for your needs - add a computer, segment, switch, change the settings, and change the connection between computers and hubs.

When a structured cable system is used, it is possible that the skin working area at the enterprise can be equipped with sockets for connecting a telephone and a computer, it is not necessary to connect it. Tobto well structured cable system will be transcendental. At the future, you can save the money, the shards of change at the connected new outbuildings, you can work for the re-switching after laying the cables.

^ The structured cable system is planned and will be ієrarchіchno, with the main line and numerical services in it (Fig. 82).

Mal. 82.ІІєrarchy of the structured cabling system
This system can be built on the basis of already existing modern telephone cable systems, in such cables, which are a set of twisted pairs, are laid in the skin, run between the tops, on the skin surface there is a special cross coat, like darts in the pipes oh and boxes are brought to the skin room and rozluchayutsya rosettes. It's a pity that our country is far from being near all the days where I'm standing again, telephone lines are laid with twisted pairs, so the stench is unsuitable for the creation of computer networks, and the cable system in such a state will need to be re-invented.

A typical hierarchical structure of a structured cable system (Fig. 83) includes:

horizontal subsystems (no more on top);
vertical subsystems (in the middle of the building);
the subsystem of the campus (in the boundaries of the same territory with the campus).

Mal. 83. Structure of cable subsystems
Horizontal subsystem behind the cross coat on top with rosettes of coristuvachiv. Subsystems of tsgogo vіdpovіdat budіvl_ tops. Vertical subsystem rear cross-sectional coat of the skin on top of the central apparatus room. Coming Croc ієrarchії є campus subsystem , yak zadnuє kіlka budіvel z head equipment of the whole campus. This part of the cable system is called backbone.

The choice of a structured cable system for the replacement of chaotically laid cables gives the business a lot of wins.

Universality . A structured cable system with a well-thought-out organization can become a single medium for transmitting computer data from a local enumeration system, organizing a local telephone network, transmitting video information and navigating signal transmission to sensors in fire safety and security systems . This allows you to automate many processes of control, monitoring and management of government services and systems of life security of business.
Extended term of service . The term of moral antiquity of a well-structured cable system can become 15 years old.
Change of vartostі adding new coristuvachіv and change their location . It seems that the quality of the cable system is important and is important not to the quality of the cable, but to the quality of the cable. For this reason, it is advisable to carry out a one-time work with laying the cable, it is possible, with a larger margin for a long, lower sprat, to lay a gasket, building up a long cable. With this approach, all robots from adding or moving the coristuvach are connected to the computer to the outlet.
Possibility of easy expansion of the mesh . Structured cabling system is modular and easy to expand. For example, it is possible to add a new subdivision to the main line, without interfering with the current subdivision. You can change the type of the cable in the nearest future, regardless of the size. The cable system is structured as the basis for the subdivision of wires on easily cored logical segments, the shards itself are already divided into physical segments.
Providing more efficient service . The cable system is structured to make it easier to maintain and troubleshooting is matched with the bus cable system. When organizing a bus cable system, one of the extensions, or with good elements, should be brought up to the top of all the lines, which is important to localize. In structuring cable systems, one segment is not divided into others, the fragments of the combined segments are built with additional concentrators. The concentrators diagnose and localize the faulty station.
arrogance . The structured cable system is able to increase the reliability, but the shards of such a system guarantee the quality of the four components, and the sum of their sum.

The first structured cabling system available in all of these types of systems was the SYSTIMAX SCS system from Lucent Technologies (formerly AT&T). Today the company Lucent Technologies is the main part of the light market. Many other companies also offer structured cabling systems such as AMP, BICC Brand-Rex, Siemens, Alcatel, MOD-TAP.
^

Choice of cable type for horizontal subsystems

Most of the designers begin the development of a structured cable system from horizontal subsystems, the shards themselves are connected to them by the end of the coristuvachi. With this stink, you can choose between shielded twisted pair, unshielded twisted pair, coaxial cable and fiber optic cable. It is possible to use a dartless line link.

The horizontal subsystem is characterized by a large number of cables (small 84), so it is necessary to conduct it to the skin socket, and in quiet rooms, where the computers are not combined in the measure. To the cable, which is victorious in horizontal conductors, there are advances in the ability to improve the quality of the wiring, as well as the integrity of its laying in the premises. On the version, a cross-connect panel is installed, which allows, for the help of short wired cables equipped with roses, to re-switch the circuit between the corystuvalnicky owners and concentrators/switches.

^ Copper conductor, unscreened cable twisted pair, є shortest core for horizontal cable subsystem Although, as a rule, coristuvachas need a higher bandwidth building, otherwise the cable system is laid in an aggressive environment, for which a fiber-optic cable is installed. Coaxial cable - the technology is outdated, as a trace of uniqueness, as it is no longer widely used in the industry. Bezdrotovy vyaz'azok є new and rich technology, prote through porіvnyalnu novelty and low perishkodostіykіst better than the borders of the scale її vikoristannya nevidpovidnymi areas.

Mal. 84. The structure of the cable system on top of that

When choosing a cable, the following indications are taken to respect: smug transmission, resistance, physical protection, electromagnetic transmissibility, price. In addition, when choosing a cable, it is necessary to repair it, as the cable system has already been installed at the enterprise, as well as the trends and prospects for the market at the moment.

Screened twisted pair, STP, allowing data to be transmitted to a larger station and to receive more nodes, lower unscreened. The presence of the screen robs you dearly and does not allow you to transmit your voice. Screened twisted couple vikoristovuetsya mainly in merzhey, scho based on the products of IBM and Token Ring, and seldom go to other local merzhey.

Unshielded twisted pair UTP due to the characteristics of smog transmission and subtrimming stands is also suitable for the installation of horizontal subsystems. Ale, the shards of it can convey this voice, it will win out more often.

However, i coaxial cable still one of the possible cable options for horizontal subsystems. Especially in the case, if the high rіven elektromagnіchkod do not allow vikoristovuvat torsion bets or small razmіri merezhі do not create great problems with the exploitation of the cable system.

Tovsty Ethernet can be combined with a thin greater smugoyu transmission, more stable to low and transmit data on a large distance, more foldable to come and less fuzzy. It is more convenient to work with Ethernet, and it is not enough for horizontal subsystems. However, it can be used in a vertical subsystem like a backbone, like a fiber optic cable, for no reason at all.

Thin Ethernet - the same cable, which can solve problems caused by thick Ethernet jamming. Prior to the advent of the 10Base-T standard, thin Ethernet was the main cable of horizontal subsystems. Thin Ethernet is easier to install, lower cost. Merezhі on a thin Ethernet can be easily picked up, the shards of the computer are connected without interruption one to one.

The main shortfall of thin Ethernet is the ease of maintenance. The leather end of the cable is to be terminated with a 50 Ohm terminator. For the power of the terminator, or use your working powers (for example, through the power of a contact) stop processing the entire segment of the wire, connecting to the same cable. Analogous consequences may not be known whether it is a working station (what is being done through the T-connector). Faults in the networks on a thin Ethernet are difficult to localize. Often bring the T-connector out of the tether adapter, test the cable segment and then repeat the procedure for all received nodes. Therefore, the variability of operation of the wire on a thin Ethernet will sound significantly higher than the variability of the operation of a similar wire on a twisting pair, if you want to capitalize on the cable system for a thin Ethernet, it will sound lower.

^ The main galuzi zastosuvannya fiber optic cable - vertical subsystem and campus subsystem. However, despite the need for a high level of data security, high throughput building or resistance to electromagnetic transitions, a fiber-optic cable can also be used in horizontal subsystems.

The versatility of the installation of a tether on a fiber optic cable for a horizontal subsystem appears to be even higher. The price is based on the size of the mesh adapters and the size of the installation robots, as in different optical fibers it is thicker, lower when working with other types of cable.

^ An important cable for a horizontal subsystem є non-screened twisted pair of category 5 .

On fig. 85 shows typical switching elements of a structured cable system, which are to be installed on the version of the laying of non-screened twists of the bet. For the shortest number of cables, a 25-pair cable is installed here and it is pink for this type of Telco cable, which can have 50 contacts.

Mal. 85. Switching elements of the horizontal cable subsystem for UTP
^

Type of cable for vertical subsystems

The cable of the vertical (or backbone) subsystem, which goes over the top of the bus, is responsible for transmitting data on a large distance, and with a greater speed, it is parallel with the cable of the horizontal subsystem. In the past, the main type of cable for vertical subsystems is coaxial. Now for whom more and more often fiber optic cable is used.

^ For vertical subsystems, the choice of cable is limited by three options.

Optical fiber - vіdminnі characteristics of throughput capacity, vіdstanі and zahistu danih; resistance to electromagnetic shifts; you can strengthen your voice, video and data. Ale, it’s expensive, it’s hard to make a vіdgaluzhennya.
Tovsty coaxial - good characteristics of throughput capacity, vіdstanі and protection of data; you can send data. And it’s easy to work with him, wanting fakhіvtsіv, yakі mаyut podіbniy dosvіd robi, chimalo.
Wide-range cable, which is victorious in cable television, is a good indicator of bandwidth and capacity; you can transmit voice, video and data. Ale, it’s even more foldable to work and use large windows for an hour of operation.

The congestion of the fiber-optic cable in the vertical subsystem may be low. It transmits data significantly more quickly without the need to regenerate the signal. Vіn may have a core of smaller diameter, so there may be spacers in the upper areas. Scattered signals that are transmitted over a new, light, and not electrical, fiber optic cable. not sensitive to electromagnetic and radio frequency shifts, On the inside of a copper coaxial cable. To make a fiber optic cable an ideal medium for data transmission for industrial enterprises. fiber optic cable no scary glare to that v_n garni for zovnіshnyoї laying. Vіn zabezpechuє more high rіven zakhistu vіd unauthorized access shards of light are easier to see, lower at the drop of the mid cable (when the light is bright, the intensity of the light changes sharply).

Fiber optic cable may be small. Vіn dorogchiy for midny cable, more expensive to manage and yogo laying. Optical fiber cable is smaller, lower coaxial. The tools that need to be installed every hour when laying and testing a fiber optic cable, may be highly versatility and folding in robots. The arrival of connectors to a fiber optic cable takes a great deal of time, and also, pennies.

In order to change the varnosti pobudovi interoverhovoї backbone on fiber optic companies, for example, AMP proponuyutnu cable system with one switching center. Sound the switching center on the skin surface, and in the future, the overhead switching center (div. Fig. 84), which connects the switching centers on the surfaces. For such a traditional scheme, the choice of a fiber-optic cable between the overheads requires a sufficient number of fiber optic cables at the switching centers of the overheads. Since there is only one switching center, then all optical cables diverge from a single cross-connect cable right up to the roses of the endian region - switches, concentrators or network adapters with fiber optic transivers.

Tovst coaxial cable is also acceptable as a trunk line, a prote for new cable systems rationally vikoristovuvat fiber optic cable, scaling wines may be a larger term of service and may be possible in the future support of high-speed cables and multimedia programs. Ale for the already basic systems, a coaxial cable serving as the backbone of the system has a lot of rock, and it needs to be upgraded. The reasons for this ubiquitous congestion were wide smuga transmission, protection from electromagnetic interference and low radio transmission.

Wanting a good coaxial cable and cheaper, lower optical fiber, but with it more foldable pratsyuvati. Vin is especially sensitive to different levels of grounding voltage, which often happens when moving from one top to the other. It is important to solve the problem. To that cable number 1 for the horizontal subsystem is a fiber optic cable.
^

Type of cable for subsystem campus

As a vertical subsystem, a fiber optic cable is the best choice for subsystems of a large number of booths, spreading at a radius of a large number of kilometers. For these subsystems, a coaxial cable is also suitable.

^ When choosing a cable for a campus, it is necessary to secure the core on the cable to the position of the recipient. To avoid the glare, it is better to choose a non-metal fiber optic cable for external wiring. For a variety of reasons, the current cable vibrates at a high-width poly- ethylene sheath. During the underground laying of the cable, the mother is responsible for a special moisture-proof coating (for boards and underground waters), as well as a metal shield for grizzlies and vandals. The vologozahisnyy cable can be prosharok with an inert gas between a dielectric, a screen and an outer shell.

^ The cable for outdoor laying is not suitable for laying in the middle of the day, shards of wine are seen when burning a large amount of smoke.

The cable system is a protocol independent medium. Attachments and functions of the communication setup of other types are important to use depending on the type of protocol used in some implementations. At zv'yazku z tsim a little further pobudova that structurization merezhi rich in what to lie in the type of accepted protocol. Merezhevі adapters, concentrators, bridges and commutators represent the largest mass type of meshing outbuildings, which are used when structuring the meshes.