Fast ethernet 100 Mbps. Technology "Fast Ethernet". Field values ​​DSAP and SSAP

Testing laboratory of "ComputerPress" carried out testing of applications for 10/100 Mbit/s interfacing cards in workstations to the Fast Ethernet standard for the PCI bus. We chose the widest cards for a given hour with a bandwidth of 10/100 Mbit / s, shards of stink can vikoristovuvatisya in Ethernet networks, fast ethernet And in different ways, and, in a different way, the promising Gigabit Ethernet technology (capacity up to 1000 Mb/s) is still mostly for connecting hard servers to the possession of the core of the network. Superimportantly important are those, which are passively owned by the fence (cables, sockets, thinly) are victorious in the fence. Well, as for the Ethernet network, a cable for torsion pairs of category 3 is sufficient, but for Fast Ethernet, category 5 is required. Rozsіyuvannya signal, filthy protection from noise can significantly reduce the throughput of the buildings of the city.

The method of testing was to assign us to the index of effective productivity (Performance / Efficiency Index Ratio - nadal P / E-index), and only then - the absolute value bandwidth. The P/E-index is calculated as a ratio of the throughput capacity of the tethered card in Mbit/s up to the degree of CPU utilization in HDCs. This index is the Galuzev standard for determining the productivity of treadmill adapters. Vіn buv introductions in order to recover the selection of resource maps of the central processor. On the right, in the fact that several adapters are used to achieve maximum productivity by using the way to achieve the most efficient operation of a large number of cycles of the computer processor. The minimum processor load and a remarkably high throughput can be of great importance for the development of a critically important business of multimedia applications, as well as tasks of a real hour.

Were protested cards, as they are most often won for work stations at corporate and local networks:

1. D-Link DFE-538TX
2. SMC EtherPower II 10/100 9432TX/MP
3. 3Com Fast EtherLink XL 3C905B-TX-NM
4. Compex RL 100ATX
5. Intel EtherExpress PRO/100+ Management
6. CNet PRO-120
7. NetGear FA 310TX
8. Allied Telesyn AT 2500TX
9. Surecom EP-320X-R

The main characteristics of testing mesh adapters are shown in Table. one . Let's explain the deakі terms, like vikoristani at the tables. Automatic appointment The speed of the lock means that the adapter itself determines the maximum possible security of the function. In addition, at the time of automatic change of speed, there is no additional adjustment when switching from Ethernet to Fast Ethernet and back is not required. Therefore, as a system administrator, it is not necessary to reconfigure the adapter and reconfigure the drivers.

Support for the Bus Master mode allows you to transfer data without intermediary between the memory card and computer memory. This is the central processor waiting until the end of other operations. Tsya vlastivist became the de facto standard. No wonder all the different cards support the Bus Master mode.

Remote Awareness (Wake on LAN) allows you to wake up your PC as needed. Tobto, blames the ability to service a PC during a non-working hour. For this purpose, there are three-contact roses on the system board and to the adapter, which are connected with a special cable (included before the delivery kit). In addition, it is necessary special keruyuche PZ. Wake on LAN technology has been expanded by the Intel-IBM alliance.

Full duplex mode allows you to transmit data at the same time in both directions, full duplex - only in one. Thus, the maximum possible throughput for the full-duplex mode is 200 Mb/s.

The DMI interface (Desktop Management Interface) gives you the ability to capture information about the configuration and resources of the PC for additional management software.

WfM (Wired for Management) specification support ensures the interoperability of the wire adapter with wire management software and administration.

For distant capture of the OS of the computer through the mesh mesh adapters take care of the special BootROM memory. This allows you to effectively hack a number of diskless workstations. Most of the tested cards had only a socket for installing BootROM; the BootROM chip itself sounds like an option, which can be fixed.

The ACPI (Advanced Configuration Power Interface) subtrip allows you to change the power supply. ACPI is a price new technology that ensures the operation of the life care system. Won go out of vikoristanny as hardware, and software zasobіv. Basically, Wake on LAN is warehouse ACPI.

The company's ability to improve productivity can give you the opportunity to increase the efficiency of the work of the treadmill. The most prominent of them are Parallel Tasking II by 3Com and Adaptive Technology by Intel. Qi cats sound buvayut patented.

Support of the main operating systems is provided by many adapters. The main operating systems can be seen: Windows, Windows NT, NetWare, Linux, SCO UNIX, LAN Manager and others.

The service life of support is evaluated by the presence of documentation, diskettes with drivers and the possibility of obtaining the remaining versions of drivers from the company's website. Chi will not leave the role played by packaging. From the point of view, the best, in our opinion, are the D-Link, Allied Telesyn and Surecom adapters. Ale, with a halo, the rіven pіdtrimki appeared for all the cards to be happy.

Call the warranty extended for the entire hour of operation of the lace adapter (pre-warranty). Sometimes they are intermingled with 1-3 fates.

Testing technique

In all tests, the remaining versions of the drivers for the integrated cards were defeated, as they were taken from the Internet servers of the respective drivers. As soon as the driver of the tiling card, allowing for some tweaking of that optimization, the installations for the merging (the cream of the Intel merging adapter) were overridden. Significantly, 3Com and Intel cards are equipped with the richest additional capabilities and functions.

Productivity vimirovannya was carried out with the help of Novell's Perform3 utility. The principle of this utility is based on the fact that a file of small size is copied from the working station to the server's partition disk, which is divided, after which the VIN is left at the server's file cache and after a specified time interval, the sound is read. Tse allows you to reach the type of memory-merezha and use the infusion of zatrimok associated with disk operations. The parameters of the utility include the initial expansion of the file, the end expansion of the file, the short change of the expansion and the hour of the test. The Novell Perform3 utility displays productivity values ​​for files of various sizes, average and maximum productivity (KB/s). To install the utility, the following parameters were set:

• Cob rozmir file - 4095 bytes
• Final size of the file - 65 535 bytes
• Croc file extension - 8192 bytes

The hour of testing with the skin file was set to 20 seconds.

In the skin experiment, a pair of the same mesh cards were tested, one of which was processed on the server, and the other - on the working station. It turns out that we are expanding our practice, the shards at the servers start to sound like specialized mesh adapters, ensuring the assignment of additional functions. And just like that - one and the same cards are installed on the server, and on the working stations - testing is carried out by all test laboratories in the world (KeyLabs, Tolly Group, etc.). The results seem to be somewhat lower, but the experiment seems to be clean, the shards on all computers are less likely to analyze the mesh maps.

Compaq DeskPro EN client configuration:

• processor Pentium II 450 MHz
• 512 KB cache
• RAM 128 MB
• hard drive 10 GB
• operating room Microsoft system Windows NT Server 4.0 w 6a SP
• TCP/IP protocol.

Compaq DeskPro EP server configuration:

• Celeron 400 MHz processor
• RAM 64 MB
• hard drive 4.3 GB
• operating system Microsoft Windows NT Workstation 4.0 c 6 a SP
• TCP/IP protocol.

Testing was carried out in the brain, if the computers were connected with a UTP Category 5 crossover cable. For an hour of testing, the cards were tested in 100Base-TX Full Duplex mode. In this mode, the throughput of buildings is seen as a thing for the account of the fact that part of the service information (for example, confirmation of the reception) is transmitted at the same time with the basic information, which is assessed. At the minds, it was possible to fix the high value of the throughput building; for example, for the 3Com Fast EtherLink XL 3C905B-TX-NM adapter, the average is 79.23 Mbps.

The processor's occupancy was killed on the server for help Windows utilities NT Performance Monitor; data was written to a log file. The Perform3 utility was run on the client, so as not to interfere with the server processor's involvement. As the processor of the server computer was beaten by Intel Celeron, the productivity of such a processor is much lower than the productivity of Pentium II and III processors. Intel Celeron wins over in a different way: it is worth noting that the fragments of the processor's vanity are shown to have a great absolute loss, in times of great absolute values, the noteworthy loss is less.

After a skin test, the Perform3 utility places the results of its work in a text file that looks like a set of data in an offensive form:

65535 bytes. 10491.49 KBps. 10491.49 Aggregate KBps. 57343 bytes. 10844.03 KBps. 10844.03 Aggregate KBps. 49151 bytes. 10737.95 KBps. 10737.95 Aggregate KBps. 40959 bytes. 10603.04 KBps. 10603.04 Aggregate KBps. 32767 bytes. 10497.73 KBps. 10497.73 Aggregate KBps. 24575 bytes. 10220.29 KBps. 10220.29 Aggregate KBps. 16383 bytes. 9573.00 KBps. 9573.00 Aggregate KBps. 8191 bytes. 8195.50 KBps. 8195.50 Aggregate KBps. 10844.03 Maximum KBps. 10145.38 Average KBp.

Display the file size, the allowed bandwidth for the selected client and for all clients (for to this particular type there is only one client), as well as the maximum average throughput of the building for the entire test. The subtracted average values ​​for the skin test were converted from Kb/s Mbit/s using the formula:
(KB x 8)/1024,
That value of the P/E index was calculated as a ratio of the throughput to the processor utilization in hundreds of cells. The average value of the P/E index was calculated based on the results of three surveys.

There is a problem with using Perform3 utility on Windows NT Workstation: when a file is written to a partitioned disk, the file is also written to the local file cache, the stars are read easily every year. The results were hostile, if not unrealistic, and there were no transfers of data like this through the mesh. In order for the programs to be able to split the partitioned disks as the primary local disks, the operating system uses a special partitioning component - the redirector, which redirects input-output requests to the array. The best minds of the robot in the process of writing a file to a partitioned disk, which is divided, redirector uses the Windows NT cache algorithm. Also, when writing to the server, a record is made in the local file cache of the client machine. And for the testing to be carried out, it is necessary that the cache was carried out only on the server. In order to avoid caching on the computer-client, the Windows NT registry had a parameter value changed, which allowed the caching to be disabled, as if the redirector was disabled. Axis yak tse bulo zrobleno:

1. Way at the Registry:

   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Rdr\Parameters

   Parameter name:

   UseWriteBehind allows write-behind optimization for writing files

   Type: REG_DWORD

   Value: 0 (per lock: 1)

2. Way at the Registry:

   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Lanmanworkstation\parameters

   Parameter name:

   UtilizeNTCaching specifies whether the redirector will override the Windows NT cache manager to cache files instead.

   Type: REG_DWORD Value: 0 (per lock: 1)

Merezhevy Intel EtherExpress PRO/100+Management adapter

The throughput of the cards and the number of processors turned out to be practically the same as those of 3Com. Below is shown how to fix the map.

new Intel controller 82559, installed on this card, ensures high productivity, especially in Fast Ethernet networks.

The technology that Intel has won in its Intel EtherExpress PRO/100+ card is called Adaptive Technology. The essence of the method is in the automatic change of hourly intervals between Ethernet packets depending on the cost of the measure. With an increase in the availability of the network between the same Ethernet packets, it dynamically increases, which allows you to change the number of calls and increase the capacity of the building. With a small amount of vanity, if the number of calls is small, the hours between packets are reduced, which also leads to an increase in productivity. The world's greatest success of this method is due to the great col- lisions of Ethernet segments, that is, to the vices, if hubs rather than commutators prevail in the topology of the network.

The new Intel technology, called Priority Packet, allows you to regulate traffic that can pass through a mesh card up to the priorities of four packets. Tse gives the opportunity to improve the speed of transmission for critically important additions.

Support for virtual local VLAN merging (IEEE 802.1Q standard).

There are only two indicators on the board - robot / day, speed 100.

www.intel.com

SMC EtherPower II 10/100 SMC9432TX/MP Intermediate Adapter

In the architecture of the map, there are two promising technologies SMC SimulTasking and Programmable InterPacket Gap. The first technology is similar to 3Com Parallel Tasking technology. Having given the results of testing for the maps of these two virobniks, it is possible to generate some notes about the effectiveness of the implementation of these technologies. It is also significant that this mesh card showed the third result in terms of productivity and P / E index, outperforming all cards, cream 3Com and Intel.

Chotiri on the map light indicator Cabin: speed 100, transfer, pull-out, duplex.

Addresses of the main Web site of the company: www.smc.com

Ethernet, don't be surprised
for the whole yogo success was by no means elegant.
Merezhevі pay may be less rudimentary
The concept of intelligence. The stench is true
send a package back to back, but we don’t
marvel at passing on data to anyone else
one of them at once. Let's fix the Ethernet
suspіlstvo, in which people can collude
one with one, only if everyone screams
overnight.

Yak i yoga
front end, Fast Ethernet vicorist method
data transmission CSMACD (Carrier Sense Multiple Access with
Collision Detection - Multiple access to the middle
control of carriers and manifestations of coli).
Behind this ancient and unreasonable acronym
hovaєtsya even simple technology. If
the Ethernet board is responsible for the notification, then
back to back, check for silence, sweat
send the package and hear it at the same time, do not
chi sent htos povіdomlennya
one hour from it. As it happened, then
offending packets do not reach the addressee. Yakscho
kolіzії not bulo, but the fee can be continued
pass the data, get out all the same check
kіlka microseconds, persh nizh new
try to send a new portion. Tse
broken in order to pay more
could work and no one could take
channel monopoly. In times of kolіzії, resentment
attach to a small
time interval, generations
vipadkovy rank, and then shy
try again to send the data.

Through the colonies
Ethernet, nor Fast Ethernet can never be reached
his maximum productivity 10
or 100 Mb/s. How only begin
increase the traffic of the city, timchasov
hustle and bustle between parcels full of packages
rush, and a lot of kolіzіy
get bigger. Real
Ethernet performance cannot be overstated
70% of the potential throughput
zdіbnosti, and maybe lower, like a line
seriously overwhelmed.

Ethernet Wicorist
rozmir package 1516 bytes, what a miracle
came up, if the wines were less created.
Today it is worth a short time, if
Ethernet wins for interoperability
servers, shards of the server and that line call
may sound great
a bunch of small bags, what
revantazhu merezhu. In addition, Fast Ethernet
imposing an exchange on the border between
outbuildings that are connected - no more than 100
meters and tse zmushue
dodatkovu oberezhnіst
designing such measures.

Cob ethernet buw
designing on the basis of bus topology,
if all the outbuildings were connected to the sleeping
cable, thin chitovstomu. Zastosuvannya
torsion bet seldom changed the protocol.
With alternative coaxial cable
the colony began at once all
stations. At vipadku with a twisted pair
vikoristovuetsya "jam" signal, like only
the station signifies the collision, then out
sends a signal to the hub, stop
rozsilaya "jam" usim
connected to a new outbuilding.

In order to
reduce re-wiring, merge with the Ethernet standard
break into segments, yaki
unite for help bridges that
routers. Tse allow to transfer
between segments there is no more necessary traffic.
Information about what is being passed between two people
stations in one segment, will not
transferred to another and cannot be called in another
vanity.

Today at
pobudovі central highway,
unite servers and vicorist
Ethernet switching. Ethernet switches can
to look like a high-shed
bagatoport bridges, yakі can
independently signify, in yakіy yoga
packet addressing ports. Switch
look at the packet headers and
rank to become a table that signifies,
where to know the next subscriber with this
physical address. Tse allow
surround the area of ​​roses all day of the package
and reduce the possibility of overflowing,
posilyuchi yogo less at the required port. Tilki
wide packs are distributed according to
all ports.

100BaseT
- big brother 10BaseT

Idea of ​​technology
Fast Ethernet was born in 1992. In sickle
offensive rock group of virobniki
united to the Fast Ethernet Alliance (FEA).
Metoyu FEA bulo yaknaishvidshe otrimati
formally honoring Fast Ethernet to the Committee
802.3 Institute of Electrical Engineers and
radio electronics (Institute of Electrical and Electronic
Engineers, IEEE)
dealing with Ethernet standards. Success
suprojuwala new technologiesі
alliance that supports: Cherry 1995 rock
all formal procedures have been completed, and
Fast Ethernet technologies have been given a name
802.3u.

From the light hand of the IEEE
Fast Ethernet is called 100BaseT. Explained
simple: 100BaseT with extensions
10BaseT standard with throughput
10 Mb/s up to 100 Mb/s. 100BaseT standard included
I have a multiple processing protocol
access to the recognition of carriers and
detection of CSMA/CD conflicts (Carrier Sense Multiple
Access with Collision Detection)
10BaseT. In addition, Fast Ethernet can be used
cables of many types, including
twisted couple. Offenses against the power of the new
standard is more important for potential
buyers, and the very heart of їm 100BaseT
appear in the distance as a path of migration
based on 10BaseT.

Golovnym
a commercial argument against the greed of 100BaseT
є those that Fast Ethernet is based on
downgraded technology. So like Fast Ethernet
the same transfer protocol
be aware that older versions of Ethernet, and
cable systems and standards
sum to switch up to 100BaseT to 10BaseT
need

less
capital investment, lower for installation
other types of high-quality meshes. Crimea
Moreover, 100BaseT shards are
continuation of the old Ethernet standard, all
instrumental procedures
analysis of work and measure, as well as
software security that works on
old Ethernet networks are to blame for this standard
save the practice.
Otzhe, the environment 100BaseT will be known
to the administrators of the measure, yak
with Ethernet. Otzhe, navchannya staff loan
less than an hour
cheaper.

SAVE
PROTOCOL

mabooth,
the most practical advantage of the new
technology has brought solutions to denial
transfer protocol is updated without change.
Transfer Protocol
CSMA/CD, whichever way you choose
are transmitted by measure from one node to another
through the cable system. For ISO/OSI model
CSMA/CD protocol є partial equal
keruvannya access to the medium (Media Access Control, MAC).
On what level is the format determined,
to whom the information is transmitted by the measure, that
way
access to the fence (or keruvannya to the fence) for
data transmission.

Name CSMA/CD
can be divided into two parts: Carrier Sense Multiple Access
and Collision Detection. From the first part of the name you can
lay down, with a rank of vuzol
the adapter detects the moment when youmu
next to send a message. Valid until
CSMA protocol
merezhu, schob signify, chi is not transmitted to
for the moment, be-yaké іnshe pov_domlennya.
How to listen to the signal that you are carrying (carrier tone),
also at the moment the fence is occupied by others
podomlennyam - merezhy vuzol switch to mode
ochіkuvannya and perebuvaє in the new, the docks of the border are not
sing. When it's in the measure
movchannya, vuzol is starting the transmission.
In fact, the data is enforced by all universities
merezhi or segment, but priymayutsya less tim
the node to which the stench is addressed.

Collision Detection-
another part of the name - to serve the permission
situation, if two or more knots are affected
nadsilat povіdomlennya overnight.
Designed with CSMA protocol, leather ready to
the transmission of the vuzol is to blame for the ear of hearing,
schob vyznachiti, chi won free. prote,
like two woozles hear at the same time,
resentment stench virishat, scho merezha is free, and sleep
transfer your packages at once. In tsіy
situations of the transferred data
superimposed one on one (merezhevі
engineers call it a conflict), and sometimes
іz pomіdomlen not to reach the item
recognition. Collision Detection
having listened to the merezh so and after the transfer
package. If there is a conflict, then
vuzol repeat transmission through vipadkovim
the rank of vibranium is an hour that
I am reconsidering that there is no conflict.

THREE TYPES OF FAST ETHERNET

Order h
saving CSMA/CD protocol, otherwise important
solutions were to design 100BaseT in such a way
rank, so that newcomer can bulo
cables of different types - like ty, scho
vikoristovuyutsya in older versions of Ethernet, so i
new models. The standard is three
modifications for the safety of robots
different types of Fast Ethernet cables: 100BaseTX, 100BaseT4
and 100BaseFX. Modifications 100BaseTX and 100BaseT4 are covered
on the twisted couple, and 100BaseFX will be split for
optical cable.

Standard 100BaseTX
Vimagaє zastosuvannya two pairs of UTP and STP. One
a couple to serve as transfers, insha - for
I will accept. Tsim vimogam vіdpovіdat two
Major Cable Standards: EIA/TIA-568 UTP
Category 5 and STP Type 1 by IBM. 100BaseTX
private security
full duplex mode when working
intermediary servers, as well as vikoristannya
a total of two out of four eight-core pairs
cable - two more bets are lost
are free and can be victorious in
nadali for expansion of possibilities
merezhі.

Vtim, yakscho vy
100BaseTX is chosen to work with vicorist for
tsy carried out Category 5, then you should
know about yoga nedolіki. Tsey cable
more expensive for other eight-core cables (for example
Categories 3). In addition, for work with him
need more punchdown blocks (punchdown
blocks), roses and switching panels,
yakі dpovіdat vimog Category 5.
It is necessary to add what for the support
full duplex mode follows
install full duplex switches.

100BaseT4 standard
wind up with more mild vimogami to
cable that is victorious. The reason for this
the furnishing that 100BaseT4 has vico
all chotiri pari for an eight-core cable: one
for transmission, otherwise for reception, and
dvі, scho lost, pratsyyut like a transfer,
so i at the reception. In this order, 100BaseT4 and reception,
that transfer of data may be subject to
three pairs. Spreading 100 Mbit/s for three bets,
100BaseT4 changes the frequency of the signal
for yoga transfer, do it less
high-yield cable. For implementation
100BaseT4 cable pass UTP Category 3 cables
5, just like UTP Category 5 and STP Type 1.

Perevaga
100BaseT4 Poles in smaller hard
help before the event. Cables Category 3 and
4 more wide, and, moreover, stinks
much cheaper, lower cables
Category 5, which should not be forgotten until
on the cob of assembly work
rely on the fact that 100BaseT4 needs all the choices
bet i scho full duplex cim
not supported by the protocol.

Fast Ethernet included
also standard for robots with bagatomodovim
optical fiber with 62.5-micron core and 125-micron
shell. 100BaseFX standard for targeting
the best on the highway - on the day
repeaters Fast Ethernet between one
budіvlі. Traditional perevagi
optical cable to standard
100BaseFX: resistance to electromagnetic
shumіv, pokrashcheny zahist danih and great
Vіdstanі mizh mirezhnymi outbuildings.

BIGUN
ON A SHORT DISTANCE

Want Fast Ethernet
є continuation of the Ethernet standard,
transition between 10BaseT and 100BaseT lines is not possible
look like a mechanical change
possession - for whom they can
you need changes in the topology of the dimension.

theoretical
inter-segment diameter Fast Ethernet mesh
warehouse 250 meters; total more than 10
vіdsotkіv theoretical mezhі razmіru
Ethernet lines (2500 meters). Tse obmezhennya
depends on the nature of the CSMA/CD protocol and
transfer rate 100Mb/s.

Yak already
it was scheduled earlier that the data is transferred
the working station is obliged to listen to the measure in
for a stretch of an hour, which allows you to perekonatisya in
those who have reached the recognition station.
Ethernet network with bandwidth 10
Mbit/s (for example 10Base5) hourly,
required work station for
eavesdropping measures like a conflict,
vynachaetsya vіdstannyu, like 512-bit
frame (frame size for tasks in the Ethernet standard)
take an hour to process one frame on
working station. For an Ethernet network from a throughput
building 10 Mb/s
2500 meters.

From the other side,
the same 512-bit frame (standard 802.3u
selects a frame of the same size as 802.3, then
є in 512 bits), which is transmitted by robot
station in the Fast Ethernet area, walk a total of 250 m,
first work station to complete yoga
processing. Yakby receiving station bula
away from the transmission station on
stand over 250 m, then the frame is instant bi
enter into conflict with the smaller frame
the lines are far away, but transmitting
station, having completed the transmission, is no longer
took down this conflict. Tom
the maximum diameter of the line is 100BaseT
250 meters.

shob
beat the allowable distance,
need two repeaters for the day
all nodes. Vidpovidno to the standard,
maximum distance between node and
repeating to become 100 meters; at Fast Ethernet,
yak i in 10BaseT, vіdstan mіzh
concentrator and work station
can revisit 100 meters. Oskilki
back-up buildings (repeat)
make dodatkovі zatrimki, really
working between the nodes can
appear even less. Tom
є wisely take everything
Vіdstanі іz deakim stock.

For robotic
great victories come to visit
optical cable. For example, possession
100BaseFX allows full duplex mode
connect a switch with another switch
or the end station, which is located on
up to 450 meters one per one.
By installing 100BaseFX full duplex, you can
z'єdnati two merezhі annex on
within two kilometers.

YAK
INSERT 100BASET

Crimea cables,
as we have already discussed, for the installation of Fast
Ethernet adapters are required for
workstations and servers, concentrators
100BaseT i, possibly, sprat
100BaseT switches.

adapters,
necessary for organizing 100BaseT events,
bear a name Ethernet adapters 10/100 Mbps.
These building adapters
100BaseT standard) independently 10
Mb/s up to 100 Mb/s. To serve a group
servers and working stations, transferred to
100BaseT, also requires a 100BaseT hub.

When enabled
server or personal computer h
adapter 10/100 remaining view signal,
what can you tell us about those who can help you
I will pass the building 100Mb/s. Yakscho
receiving station (more for everything, tse
will be a concentrator) can be covered by
robot with 100BaseT, you can see the signal,
i hub, i PC chi server
automatically switch to 100BaseT mode. Yakscho
concentrator works only with 10BaseT, no
sends a signal to the vidpovid, i PC or server
automatically switch to 10BaseT mode.

In times
small-scale 100BaseT configurations are possible
zasosuvati mist or commutator 10/100, yaki
secure the call of the part of the merezhі that works
100BaseT, with already existing mesh
10BaseT.

DECEIVED
SHVIDKIST

Summing up everything
vyshcheskazan, respectfully, scho, how do we get it,
Fast Ethernet is the best way to solve problems
high peaks. For example, like
xtos іz koristuvachіv pratsyuє z CAD аbo
image processing programs
require an upgrade of the pass
Please note that Fast Ethernet may appear
garnimoy exit from the camp. However, always
viklikana problems over the number
koristuvachіv merezhi, then 100BaseT start
galvanized exchange of information at approximately 50-hundred
zavantazhennya merezhі - in other words, on the same
equal, scho and 10BaseT. Ale zreshtoyu, tse
even no more than lower expansion.

Fast Ethernet - specification IEEE 802.3 and officially adopted on 26 June 1995 is the standard for a channel layer protocol for networks operating with both a medium and a fiber optic cable with a speed of 100 Mb / s. New specification to reduce the Ethernet IEEE 802.3 standard, adopting such a frame format, a CSMA/CD media access mechanism and a star topology. The evolution came up with a number of elements in the configuration of the physical level, which made it possible to increase the capacity of the building, including the type of cable, the length of the segments and the number of concentrators.

Physical Riven

The Fast Ethernet standard defines three types of Ethernet signal transmission media with a speed of 100 Mbps.

· 100Base-TX - two twisted pairs of wires. The transmission is up to the data transmission standard for a twisted physical medium, rozroblenny ANSI (American National Standards Institute - American National Standards Institute). The torsion transmission cable may or may not be shielded. Vikoristovu 4V/5V data coding algorithm and MLT-3 physical coding method.

· 100Base-FX - two lived, fiber-optic cable. The transmission is also up to the data transmission standard of the fiber optic medium, as decoded by ANSI. Vikoristovu 4V/5V data coding algorithm and NRZI physical coding method.

· 100Base-T4 - this is a special specification, broken down by the IEEE 802.3u committee. Depending on the specification, data transmission is based on twisted-pair telephone cable, which is called a category 3 UTP cable. The 8V/6T data encoding algorithm is based on the NRZI physical encoding method.

Bagatomode cable

A fiber-optic cable of this type has a fiber with a core diameter of 50 or 62.5 micrometers and an outer sheath of 125 micrometers. Such a cable is called a multimodal optical cable with 50/125 (62.5/125) micrometer fibers. To transmit a light signal over a multi-mode cable, a light receiver with a long wind of 850 (820) nanometers is installed. Like a multi-modal cable, it connects two ports of jumpers, which work in full duplex mode, up to 2000 meters.

Single mode cable

A single-mode fiber-optic cable is smaller, lower for a multi-mode fiber, the diameter of the core is 10 micrometers, and for transmission over a single-mode cable, a laser receiver is used, which in total ensures safety efficient transmission great distances. The length of the light signal that is being transmitted is close to the diameter of the core, which is 1300 nanometers. This number seems to be a long time of zero variance. In a single-mode cable, the dispersion and loss of the signal are even insignificant, which allows the transmission of light signals of great width, lower than the time of multimode fiber.

38. Technology Gigabit Ethernet, the main characteristic of the specification of the physical medium, the main understanding.
3.7.1. Zahalna characteristic to the standard

Finish quickly after the appearance on the market of Fast Ethernet products, mesh integrators and administrators, led the way for the facilitation of corporate meshing. In a variety of configurations, the servers, connected by a 100-megabit channel, were switched over the backbones of the network, which also work on the speed of 100 Mbps - the backbone of FDDI and Fast Ethernet. There was a need for a equal hierarchy of shvidkos. In 1995, the founding of the RIVENSKOSTII could have been the Licha Romutator atm, and for the same time at that hour of the vigorous post -migration technology in the local grace (I did the specify emulation - Lane is the fact of the rosya, practical realizes, practical realiza. mezhe mayzhe no one cares. In addition, ATM technology vyrіznyalas even higher level vartosі.

To this, it is logical to look at the upcoming crack, the destruction of the IEEE - 5 months after the residual adoption of the Fast Ethernet standard in Cherry 1995, the year of the last group of development of high-speed technologies of the IEEE was punished to look at the possibility of the development of a high-speed Ethernet standard with a larger version.

In the spring of 1996, the creation of the 802.3z group was announced to develop a protocol that was most similar to Ethernet, but with a 1000 Mbps bit rate. As a matter of fact, Fast Ethernet has been adopted by Ethernet adapters with great enthusiasm.

The main reason for the enthusiasm was the prospect of such a smooth transfer of the merging backbones to Gigabit Ethernet, similarly to the fact that the Ethernet segments were transferred to Fast Ethernet, roztashovani on the lower levels of the tiers. Until then, data transmission on gigabit ports is already used, both in territorial networks (SDH technology), and in local ones - Fiber Channel technology, as it is mainly used for connecting high-speed peripherals to large computers and transmitting data via fiber-optic cable. speed, close to gigabit, for the help of the superfluous code 8V / 10V.

The first version of the standard was reviewed in September 1997, and the rest of the 802.3z standard was adopted on March 29, 1998 at a meeting of the IEEE 802.3 committee. Robots for the implementation of Gigabit Ethernet on torsion pairs of category 5 were transferred to a special committee 802.3ab, which had already considered some options for the draft standard, moreover, from the fall of 1998, the project began to achieve a stable character. Remaining praise for the 802.3ab standard is cleared in the spring of 1999.

Despite the adoption of the standard, the companies released the first Gigabit Ethernet on fiber optic cable before the summer of 1997.

The main idea of ​​the distribution of the Gigabit Ethernet standard is based on the maximum savings of the ideas of the classic Ethernet technology with a bit rate of 1000 Mb/s.

So, as with the development of new technology, it is natural to recognize some technical innovations that go in the wild for the development of merging technologies, it is important to note that Gigabit Ethernet, as well as smaller swidkish brothers, on a par with the protocol won't subtly:

• service quality;
• superfluous links;
• testing the availability of nodes and having it (in the rest of the case - testing the connection between a port and a port, as it should be done for Ethernet 10Base-T and 10Base-F and Fast Ethernet).

All three titles of authority are considered even more promising and similar to the modern fences, and especially to the fences of the nearest future. Why are the authors of Gigabit Ethernet talking about them?

The main idea of ​​the retailer of Gigabit Ethernet technology lies in the fact that it will be used and will be high speed backbones and the ability to assign priority packages to commutators will be sufficient to ensure the quality of transport services for all customers in the network. And only in quiet rare weather, if the main line is busy, and if the service level is too hard, it is necessary to stop the ATM technology, as it is effectively for the high complexity of the day, we guarantee the quality of the service for all the basics.

39. Structural cable system, which zastosovuetsya in fencing technologies.
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 are 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. If necessary, the configuration of the calls can be easily changed - add a computer, segment, switch, more inappropriately equipped, and also 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. So a 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.

A typical hierarchical structure of a structured cabling system includes:

• horizontal subsystems (at the boundary on top);
• vertical subsystems (in the middle of the building);
• subsystem of the campus (between the same territory and kіlkom booths).

Horizontal subsystem behind the cross coat on top with rosettes of coristuvachiv. Subsystems of this type can be applied to the tops of everyday life. 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 entire campus. This part of the cable system is called backbone.

The choice of a structured cable system and the replacement of chaotically laid cables gives the enterprise a lot of advantages.

· Universality. A structured cable system with a thoughtful organization can become a single medium for the transfer of computer data from a local billing system, a local organization telephone line, transmitting video information and navigating the transmission of signals to sensors in fire safety or security systems. This allows you to automate many processes of control, monitoring and management of government services and systems of life security of business.

· Improved term of service. The term of moral antiquity of a well-structured cable system can become 10-15 years old.

· Changing the vartosti adding new coristuvachiv and changing their place of placement. 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 a basis for subdivision on easy keratinization of logical segments, to that it is already divided into physical segments.

· Providing efficient service. The cable system was structured to make it easier to maintain and check for faults at 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.

· Hopefulness. 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.

40. Hubs and mesh adapters, principles, vikoristannya, basic concepts.
The concentrators at the same time with meshing adapters, as well as the cable system, represent the minimum possession, for the help of which you can create a local mesh. Such a mesh will be a blazing middle ground that is divided.

Merezhevy adapter (Network Interface Card, NIC) Together with its driver, it implements another, channel version of the model of critical systems at the end node of the network - a computer. More precisely, in the operating system, the adapter and driver pair only functions of the physical and MAC-level, at that time, the LLC-level is implemented by the operating system module, which is the same for all drivers and network adapters. It is not so easy and may be compatible with the IEEE 802 protocol stack model. For example, in Windows NT operating system Rivene LLC is implemented in the NDIS module, which is common for all drivers and network adapters, regardless of whether the technology supports the driver.

Merezhevy adapter is connected to the driver in two operations: transmission and reception of a frame.

For adapters for client computers, a significant part of the work is transferred to the driver, the cim adapter is simpler and cheaper. The shortfall of such an approach is the high cost of the central processor of the computer by routine robots transferring frames from the computer's operational memory in the measure. The central processor of disturbances will be engaged in the work of the vice-president of applied tasks of the coristuvach.

Before installing the computer, it is necessary to configure the media adapter. When configuring the adapter, the number and reset of the IRQ assigned by the adapter are set, the number of the direct access channel to the DMA memory (thus the adapter supports DMA mode) and the base address of the input/output ports.

Almost all modern technologies local borders were assigned attachments, which may be a sprat of equal names concentrator(Concentrator), hub (hub), repeater (repeater). Fallow in the area of ​​zastosuvannya of which I will add a significant world, the warehouse of its functions and constructive vikonannia is changing. The main function is lost forever - ce frame repetition or on all ports (as designated by the Ethernet standard), or only on other ports, depending on the algorithm designated by the standard.

The concentrator sounds a lot of ports, which, for the help of okremyh physical segments, are connected to the cable to the terminal nodes of the network - computers. The concentrator combines two physical segments of a network in a single medium that is divided, access to which is possible is dependent on one of the examined protocols in local networks - Ethernet, Token Ring, etc. technologies, then for the skin type of technology, their own hubs are produced - Ethernet; token ring; FDDI and 100VG-AnyLAN. For a specific protocol, it has its own, highly specialized name, which more accurately mimics its function, or it is traditionally won, for example, for Token Ring concentrators, the name MSAU is typical.

The skin concentrator vikonu the main function, assigned to the advanced protocol of technology, as a violin support. If this function is specified in detail in the technology standard, the implementation of the concentrators of various types can be adjusted with such details as the number of ports, the number of cables and the number of cable types.

For the main functions, the concentrator can include a number of additional functions, which are either not specified in the standard, or are optional. For example, a Token Ring concentrator can enable the port-on function, which is incorrectly handled, and transferred to the backup ring, although this capability is not described in the standard. The concentrator appears as a handy extension for additional functions, which makes it easier to control and operate the device.

41. Vykoristannya bridges and commutators, principles, features, applications
Structurization behind auxiliary bridges and commutators

The mesh can be divided into logical segments behind an additional extension of two types - bridges (bridge) and / or commutators (switch, switching hub).

Mist and commutator - tse functional twins. Offended by the attachments, they put the frames on the stands of the algorithms themselves. Bridges and commutators use two types of algorithms: the algorithm transparent bridge (transparent bridge), described in the IEEE 802.1D standard or the algorithm bridge from routing to Dzherel (source routing bridge) IBM for Token Ring Merez. These standards were expanded long before the appearance of the first commutator, so the term "bridge" stinks. If the first industrial switch model for Ethernet technology appeared in the world, it won the same algorithm for pushing frames IEEE 802.ID, which was a dozen decades of bridges of local and global networks

The main function of the commutator is in the bridge for the one that processes the frame sequentially, and the commutator in parallel. This situation is due to the fact that the bridges appeared at that hour, if the line was divided into a small number of segments, and the inter-segment traffic was small (when the order was 80 by 20%).

Today, bridges, like before, work at the treadmills, but only to achieve more global connections between two distant local treadmills. Such bridges are called remote bridges, the algorithm of their work does not comply with the 802.1D standard or Source Routing.

Transparency at the same time, frame transmission at the borders of the same technology, translating the protocols of local networks, for example Ethernet at Token Ring, FDDI at Ethernet is just that. The power of transparent bridges is described in the IEEE 802.1H standard.

Nadali are called attachments, which put frames behind the bridge algorithm and work in the local area, the current term "switch". When describing the algorithms themselves 802.1D and Source Routing in the offensive division, we will traditionally call attachments a bridge, as well as it is called in these standards.

42. Switchboards for local merezh, protocols, modes of work, applications.
A skin of 8 10Base-T ports is served by one Ethernet packet processor - EPP (Ethernet Packet Processor). In addition, the switcher is a system module that coordinates the work of all EPP processors. The system module maintains the address table of the switch and manages the switch using the SNMP protocol. For the transfer of frames between ports, a switching matrix is ​​used, similar to those used in telephone switches or multiprocessor computers, linking several processors with several memory modules.

The switching matrix is ​​based on the principle of switching channels. For 8 ports, the matrix can provide 8 one-hour internal channels in full-duplex mode and 16 in full-duplex mode, if the skin port transmits and receives independently one to one.

When a frame is needed before any port, the EPP processor buffers some of the first bytes of the frame in order to read the destination address. After accepting the address, the processor immediately accepts a decision about the transmission of the packet, not checking the arrival of other bytes in the frame.

If the frame needs to be transferred to another port, the processor will go to the switching matrix and try to install it in it, which calls port to port, through some route to the destination address. The switching matrix can only work if the port of the address is recognized at the moment is not allowed to connect to another port. As a port of employment, then, as in the case of an extension with switching channels, the matrix is ​​in the control room. In this case, the frame is buffered again by the processor of the input port, after which the processor checks the signal of the output port and the switching matrix of the input port is approved. Just as the processor of the outgoing port denies access to the Ethernet segment connected to the new one using the CSMA / CD algorithm, bytes of the frame are immediately started to be transmitted to the media. Descriptions of the method of transmitting a frame without any re-buffering, omitting the name of the commutation "on-the-fly" or "cut-through". The main reason for the increase in the productivity of the measure is the hour of the switching of the commutator parallel processing of a few shots. The effect is illustrated in Fig. 4.26. The little picture shows an ideal way to increase the productivity of the situation, if two or more ports from eight transmit data with a maximum speed for the Ethernet protocol of 10 Mb / s, moreover, the stench transmits data to the port of which the ports of the switch do not conflict - the data flows were so similar to the nodes skin receiving frame port є svіy vyhіdny port. If the switcher is able to process the input traffic for the maximum intensity of the need for frames on the input ports, then the total productivity of the switcher at the pointed butt becomes 4x10 = 40 Mbit/s, and when the butt is assigned N ports - (N/2)xlO Mbit/s. It seems that the switch is giving a skin station, or the segment connected to this port has seen the throughput of the protocol. Naturally, in a measure, such a situation does not always develop, as shown in Fig. 4.26. Like two stations, for example, stations connected to ports 3 і 4, one hour it is necessary to write data to the same server, connections to the port 8, then the switch can see the skin station streaming data at 10 Mb/s, while port 5 is unable to transmit data at 20 Mb/s. Personnel of the stations are checked at the inner doors of the entrance ports 3 і 4, when the port calls 8 transfer of the draft frame. Obviously, solutions for such a distribution of data flows, it would be necessary to connect the server to a larger high-speed port, for example, Fast Ethernet. non-blocking switcher models

43. Robotic transparent bridge algorithm.
The gaps are unfamiliar for smaller adapters of terminal nodes, as they will independently create a special address table, on the basis of which it is possible to view, it is necessary to transmit a frame, which has arrived, to any other segment of the world. Merezhevі adapters with vikoristannye prozorikh bridges work the same way, like at different times of daytime, so as not to shy away the daily supplementary work, so that the frame passes through the city. The transparent bridge algorithm cannot be found in the technology of a local network, in which place it is installed, Ethernet transparency is treated the same way as FDDI transparency.

Prozory will place its address table on the basis of a passive watch for traffic that circulates in connected to the first port segments. At the same place, the address of the cadres of the data, who should be on the bridge, was sent. Behind the address of the dzherel frame, there is a place to make a visnovok about the relevance of this knot to that other segment of the chain.

Let's take a look at the process of automatic creation of the address table on the bridge and on the butt of a simple fence, shown in fig. 4.18.

Rice. 4.18. The principle of robotic transparent bridge

Place over two logical segments. Segment 1 is composed of computers, connected with the help of one additional coaxial cable to bridge port 1, and segment 2 - computers, connected with the help of another coaxial cable to bridge port 2.

The leather port to the bridge works like the last node of its segment for one fault - the port to the bridge does not have a valid MAC address. The port of the bridge works at the so-called indistinct (promisquous) packet hopping mode, if all packets arriving at the port are stored in the buffer memory. For the help of such a regime, there is a place to follow all the traffic that is transmitted in the arriving to the new segments, and vicorist packets that go through the new one, for the storage of goods. Since all packets are written to the buffer, then the bridge does not need addresses for the port.

AT outside station Mist knows nothing about those computers with some MAC addresses connected to the skin port. To that, in this way, the mist is simply passed on, whether it’s a blockage or a buffering frame for all its spoils, for the blame of what kind of frame was taken. Our butt of the bridge has less than two ports, to that port it sends frames from port 1 to port 2, and on the other hand. If the place is chosen to transmit a frame from segment to segment, for example, from segment 1 to segment 2, then again it is possible to take access to segment 2 as the final rule for the access algorithm, this butt- Behind the rules of the CSMA/CD algorithm.

At the same time, with the transfer of the frame to all ports of the city, the address of the dzherel frame is to be robbed new entry about its existence in its address table, as it is called a filtering table or a routing table.

In addition, as the place of the first stage of training, you can practice more rationally. When you take a frame, directly, for example, from computer 1 to computer 3, you look at the address table for the purpose of finding the address with the address assigned 3. yuteri with dzherel addresses (in our case - tse address 1) and the address assigned (address 3) in one segment. Since our butt has stench in different segments, then the place of operation forwarding frame – transmitting a frame to another port, prioritizing access to another segment.

If the address of recognition is unknown, then the place transmits the frame in all its damages, to the Crimean port - dzherela the frame, as in the first stage of the process of starting.

44. Bridges with dzherel routing.
Bridges with routing from the dzherel are installed for the connection of Token Ring and FDDI, although for these purposes they can be victorious and clear. Source Routing (SR) is based on the fact that the source routing station puts in the frame, which is used in another country, all the address information about the area and the country, if it is guilty to go through the frame before it, how to spend it in the country, until otrimuvach station is connected.

Let's take a look at the principles of the work of Source Routing bridges (nadal, SR-bridges) from the butt of the mesh shown in fig. 4.21. Merezha is built up from three villages, connected by three bridges. For zavdannya route kіltsya that bridges may іdentifіkatori. SR-bridges do not have an address table, and when passing frames, they display information that is in the data frame's data fields.

Rice. 4.21.Bridges to type Source Routing

When retrieving the skin packet, the SR-bridge needs to look at the routing information field (the Routing Information Field, RIF, in the Token Ring or FDDI frame) to make it clear in the new identifier. If it is present there and is accompanied by a ring identifier, if it is connected to this bridge, then in this way there is a copy of the frame that is supposed to be in the designated ring. In a different way, a frame in a different ring is not copied. If the copy of the frame is rotated according to the output ring of the station-director, and if the number of transmissions in the other ring, then bit A (recognition addresses) and bit C (copy frame) of the status field of the frame are set to 1, so that the station will to the official, that the frame was taken by the recognition station (at times of transmission by the bridge in another ring).

Since the routing information in the frame is not required, but only for transmitting the frame between stations connected to different circuits, the presence of the RIF field in the frame is indicated by setting the individual / group address (I / G) to 1 bit acknowledgment, oskіlki address dzherel zavzhdi іndivіdualna).

The RIF field is a small subfield that is made up of three parts.

• frame type Specifies the type of the RIF field. Іsnuyut different types fields of RIF, which are chosen for the direction of the route and for correcting the frame behind the route.
• Maximum frame length field vikoristovuetsya bridge zv'yazku kіlets, yakim installed different MTU values. For the help of this field, the city informs the station about the maximum possible frame length (to ensure the minimum MTU value for the shortest warehouse route).
• Dovzhina RIF field it is necessary, oscillki zazdalegіd nevіdoma kіlkіst opisnіkіnіn route, scho to set іdidentificatorі kіletsі і bridges, scho intertwined.

For the operation of the router routing algorithm, two additional frame types are used - a single-route wide frame-last SRBF (single-route broadcast frame) and a multiple-route wide frame-last ARBF (all-route broadcast frame).

The SR-bridges must be manually set by the administrator in order to transmit ARBF frames to all ports, the port-dzherela frame, and for SRBF frames, it is necessary to block the bridges, so that there are no loops on the bridge.

Advantages and shortcomings of bridges from routing to Dzherel

45. Switchers: technical implementation, functions, indicators, what to add to the robot.
Features of the technical implementation of commutators. A lot of switches of the first generation were similar to routers, so they were grounded on central processor vulgar recognition, connected with the interface ports of the internal swedish bus. The main shortcoming of such commutators was their low speed. The universal processor could not immediately come into contact with a great deal of special operations from the transfer of personnel between interface modules. The cream of processor microcircuits for successful non-blocking robots and the switcher needs a mother swidcode vuzol for transferring frames between processor microcircuits of ports. In this hour, the commutator will switch as a basic one of three schemes, for which there will be such an exchange vuzol:

• switching matrix;
• rich memory that is divided;
• hot tire.

The widest range of standard Ethernet tethers is the Ethernet tether. First it appeared in 1972 (Xerox was the retailer). Merezha seemed to finish off in the distance, and after that, in 1980, such largest companies, like DEC and Intel, were promoted (the association of these companies was called DIX after the first letters of their names). With efforts in 1985, Ethernet became an international standard, її accepted by the largest international organizations for standards: Committee 802 IEEE (Institute of Electrical and Electronic Engineers) and ECMA (European Computer Manufacturers Association).

The standard is called IEEE 802.3 (it reads eight oh two dot three in English). Vіn assigns multiple access to a monochannel to the bus type with conflict detection and transmission control, that is with the CSMA / CD access method, which is already a guess. This standard was satisfied with deyakі іnshі merezhi, oskolki rivenі yogo detalіzatsії not high. As a result, measures to the IEEE 802.3 standard were often inconsistent between themselves, both for constructive and electrical characteristics. However, for the rest of the hour, the IEEE 802.3 standard is respected by the Ethernet network standard.

The main characteristics of the cob standard IEEE 802.3:

• topology - bus;
• transmission medium - coaxial cable;
• speed of transmission - 10 Mbit / s;
• the maximum length of the merezhі is 5 km;
• maximum number of subscribers - up to 1024;
• valley of the merezhі segment - up to 500 m;
• number of subscribers per segment – ​​up to 100;
• access method - CSMA/CD;
• Vuzkosmugov transmission, without modulation (monochannel).

Strictly seeming, between IEEE 802.3 and Ethernet standards, there are some insignificant details, but you should not guess about them.

The Ethernet network is currently the most popular in the world (more than 90% of the market), it is possible that such a won and be lost in the nearest future. What a significant world was taken by those who, from the very beginning of the characteristics, parameters, protocols of the measures, were recognized, after which the great number of virobniks in the world began to launch Ethernet equipment, as I will sum up among myself.

The classic Ethernet cable has a 50-ohm coaxial cable of two types (thin and thin). However, in the last hour (since the beginning of the 90s) the largest version of Ethernet appeared, as a victorious as the medium of transmission of twisted bets. A standard has also been drawn up for laying in a fiber optic cable. For vakhuvannya tsikh zmin to cob standard IEEE 802.3 was zrobleno vіdpovіdnі dаvannya. In 1995, a new standard appeared for a larger version of Ethernet, which works on a speed of 100 Mbit / s (the so-called Fast Ethernet, IEEE 802.3u standard), which is twisted like a transmission medium, or a fiber optic cable. In 1997, a 1000 Mbit/s version was released (Gigabit Ethernet, IEEE 802.3z standard).

Crimean standard bus topology is becoming more and more popular with passive star topology and passive tree topologies. At the same time, the number of repeaters and repeater concentrators are transmitted, which can be obtained among themselves by different parts (segments) of the merezhi. As a result, a tree-like structure can be formed on segments of various types (Fig. 7.1).

Rice. 7.1. Classic Ethernet network topology

Like a segment (parts of a merezhі) can be a classic bus or a single subscriber. For bus segments, a coaxial cable is used, and for changing a passive mirror (for connecting to a single computer hub), a pair of fiber optic cables is twisted. The main thing is to take away topology from the beginning - sob it has closed paths (loops). In fact, to get out, that all subscribers are connected to the physical bus, so the signal from the skin to them expands on all sides and does not turn back (like in the ring).

The maximum length of the cable as a whole (the maximum road for the signal) theoretically can reach 6.5 kilometers, but practically does not exceed 3.5 kilometers.

At the Fast Ethernet network, the physical topology of the bus is not transferred, only a passive star or a passive tree is chosen. Before that, Fast Ethernet has a lot of zhorstkіshі vomogi to the boundary line of the border. Even with a 10-fold increase in the speed of transmission and saving the format of the package, the minimal cost becomes ten times shorter. In this way, the value of the subway hour of the signal passing by the measure changes for 10 times (5.12 µs versus 51.2 µs Ethernet).

For transmission in an Ethernet network, the standard Manchester code is used.

Access to the Ethernet network is controlled by the CSMA/CD vipadkovym method, which ensures the equality of subscribers. At mezhі vikoristovuyut packages zminnoї dozhini zі structure, presented in fig. 7.2. (numbers show the number of bytes)

Rice. 7.2. Structure of an Ethernet network packet

The length of an Ethernet frame (tobto a packet without a preamble) can be no less than 512 bit intervals or 51.2 μs (the same limit value of the transit time in the network). Transferred to individual, group and wide addressing.

An Ethernet packet has the following fields:

• The preamble is composed of 8 bytes, the first symbol is the code 10101010, and the remaining byte is the code 10101011. In the IEEE 802.3 standard, eight bytes are called the Start of Frame Delimiter sign (SFD - Start of Frame Delimiter) and set the packet field.
• The addresses of the owner (receiver) and the sender (transmitter) include 6 bytes each and will follow the standard described in the section. Addressing the packets in the lecture 4. The number of address fields are processed by the subscribers' equipment.
• Control field (L/T - Length/Type) to retrieve information about the length of the data field. It can also designate the type of protocol to win. It is accepted that if the value of this field is not more than 1500, it indicates the value of the data field. Any value greater than 1500 will determine the frame type. The field of keruvannya is processed programmatically.
• The data field can include 46 to 1500 bytes of data. If the packet is guilty of storing less than 46 bytes of data, the data field is padded with the bytes of the data. Applies to the IEEE 802.3 standard, the packet structure has a special padding field (pad data - insignificant data), as well as a zero value, if there is enough data (more than 46 bytes).
• The checksum field (FCS - Frame Check Sequence) contains a 32-bit cyclic checksum of the packet (CRC) and serves to verify the correctness of the packet transmission.

Thus, the minimum length of a frame (packet without a preamble) is 64 bytes (512 bits). The value itself defines the maximum allowable latency of a constant signal over 512 bit intervals (51.2 µs for Ethernet or 5.12 µs for Fast Ethernet). The transmission standard, that the preamble can change when the packet passes through different buildings, is not guaranteed. The maximum frame length is 1518 bytes (12144 bits, which is 1214.4 µs for Ethernet, 121.44 µs for Fast Ethernet). It is important for the choice of the buffer memory of the merezhny possession and the assessment of the global interest of the merezh.

The choice of the preamble format is not customary. On the right, in the fact that the sequence of ones and zeros (101010 ... 10), which are drawn, in the Manchester code is characterized by time, which can only pass in the middle of bit intervals (div. section 2.6.3), then only informational transitions. Insanely, priymachevi just nalashtuvatsya (synchronization) for such a sequence, navіt as if there is a reason for a short bit. The rest of the two single bits of the preamble (11) are currently suspended in sequence 101010…10 (they are transitional between bit intervals). For this reason, even after the acquisition, you can easily see and detect the cob of brown information (the cob of the frame).

For an Ethernet network, which operates at a speed of 10 Mb/s, the standard defines the following main types of segments in the network, oriented to different media of transmission of information:

• 10BASE5 (common coaxial cable);
• 10BASE2 (thin coaxial cable);
• 10BASE-T (twisted pair);
• 10BASE-FL (fiber optic cable).

The name of the segment includes three elements: the number 10 means the speed of transmission of 10 Mb/s, the word BASE - transmission to the main frequency mix (so without modulation of the high-frequency signal), and the remaining element - the allowable length of the segment: 5 - 500 meters, 2 - 200 meters ( more precisely, 185 meters) or the type of the link line: T - twisted pair (English twisted-pair), F - fiber optic cable (English fiber optic).

So for the Ethernet network itself, which works on the speed of 100 Mbit / s (Fast Ethernet), the standard defines three types of segments, which are considered by the types of transmission medium:

• 100BASE-T4 (quad twisted pair);
• 100BASE-TX (double twisted pair);
• 100BASE-FX (fiber optic cable).

Here the number 100 means the speed of transmission of 100 Mbit / s, the letter T - twisted pair, the letter F - fiber optic cable. Types 100BASE-TX and 100BASE-FX can sometimes be combined under the names of 100BASE-X, and 100BASE-T4 and 100BASE-TX - under the names of 100BASE-T.

The report on the features of the Ethernet equipment, as well as the algorithm for managing the CSMA/CD exchange and the algorithm for calculating the cyclic checksum (CRC) will be reviewed further in the special sections of the course. Here, only those who do not rely on record-breaking characteristics or optimal algorithms should be considered, only those that are not supported by a number of parameters in other standard networks. Ale zavdyaki potuzhnіy pіdtrimtsi, the most equal of standardization, majestic obligations of release technical aids, Ethernet can be seen in the middle of other standard measures, and so be it else mesh technology taken over by itself with Ethernet.

The development of Ethernet technology is moving towards an ever-larger entry into the cob standard. Zastosuvannya new transmission mediums and commutators allow the suttєvo zbіshiti rozmіr mezhі. Vіdmova vіd Manchester code (for Fast Ethernet and Gigabit Ethernet systems) ensures more data transmission security and lowers the cable. The control method CSMA/CD (with full-duplex exchange mode) gives you the ability to dramatically increase the efficiency of the work of taking the exchange from the house. Prote, all new types of networks are also called Ethernet networks.

Merezha Token-Ring

The Token-Ring (marker ring) was propagated by IBM in 1985 (the first version appeared in 1980). The won was assigned to the union of all types of IBM computers. Even though the fact that I support IBM, the largest manufacturer of computer technology, to talk about those who need to add special respect. But not less important are those that Token-Ring is in Denmark the international standard IEEE 802.5 (although Token-Ring and IEEE 802.5 are insignificant). Tse put given merezh for one price per status from Ethernet.

The development of Token-Ring is a great alternative to Ethernet. If you want Ethernet to close the network at once, Token-Ring cannot be used hopelessly old. Over 10 million computers in the whole world are united by a network.

The IBM company worked hard to expand its capabilities to the maximum extent possible: the report documentation was issued right up to important schemes adapters. As a result, a lot of companies, for example, 3COM, Novell, Western Digital, Proteon and others have started to develop adapters. Prior to speech, especially for the company, as well as for other companies of the IBM PC Network, the concept of NetBIOS was expanded. While the NetBIOS software was saved from the built-in resident memory adapter in the earlier creation of the PC Network, the NetBIOS program was already stuck in the Token-Ring system. This made it possible to react more strongly to the peculiarities of the equipment and to enhance the summation of the programs of the highest level.

Merezha Token-Ring may be a ring, wanting to call it out more guess the sky. The reason is that some subscribers (computers) are connected to the measure without intermediary, and through special concentrators or rich station access units (MSAU or MAU - Multistation Access Unit). Physically, the mesh establishes the mirror-kilts topology (Fig. 7.3). In fact, the subscribers are united all the same in the ring, so that from them they transmit information to one land subscriber, and receive information from another.

Rice. 7.3. Zirkovo-kiltseva topology of the Token-Ring network

The concentrator (MAU) allows its centralization of the configuration, the inclusion of faulty subscribers, and the control of the operation of the network. (Fig. 7.4). Any data processing is not processed.

Rice. 7.4. Calling up subscribers in the Token-Ring network at the back of the auxiliary concentrator (MAU)

For a skin subscriber, a special unit for connecting to the trunk (TCU - Trunk Coupling Unit) is installed at the concentrator warehouse, which ensures auto-on the subscriber in the ring, yakscho vin connections to the concentrator and reference. If the subscriber is connected to the concentrator or the fault is not correct, then the TCU automatically checks the integrity of the ring without the participation of the subscriber. Ask the TCU for the signal fast strumu(So ​​the titles of phantom strum), which come from the subscriber, which is supposed to turn on in the ring. The subscriber can also choose to perform a self-test procedure (the rightmost subscriber in Fig. 7.4). The phantom strum does not flow into the informational signal, the shards of the signal are not at the warehouse.

Structurally, the hub is an autonomous block with ten sockets on the front panel (Fig. 7.5).

Rice. 7.5. Token-Ring Hub (8228 MAU)

Vіsіm central nests (1...8) are designated for connecting subscribers (computers) for additional adapter cables (Adapter cable) or radial cables. Two extreme roses: input RI (Ring In) and output RO (Ring Out) serve to connect to other concentrators for additional special backbone cables (Path cable). Proponuyutsya real and floor options of the concentrator.

Use both passive and active MAU concentrators. An active hub sends a signal to the subscriber (it works like an Ethernet hub). A passive concentrator does not pick up the signal, it just changes the line connection.

The concentrator at the merezhі can be single (as in Fig. 7.4), in which case in the ring there are less subscribers who are connected to the new one. Such a topology looks like a star. If it is necessary to connect up to a number of more than eight subscribers, then the concentrators are connected by main cables and establish a mirror-kilts topology.

As it was intended, the ring topology is more sensitive to the ears of the ring cable. To improve the survivability of the thread, Token-Ring transfers the mode of the so-called ringing of the ring, which allows you to get around the place of shaving.

In normal mode, the concentrators are connected in the ring with two parallel cables, but the transfer of information is carried out only by one of them (Fig. 7.6).

Rice. 7.6. Combining MAU concentrators in normal mode

At the time of a single shave (shaving) to the cable of the merging, transmission is carried out along both cables, obminating the sim of the squished parcel. For whom to navigate, the procedure for bypassing subscribers connected to concentrators is selected (Fig. 7.7). Truth is, the sumarna dozhina of the hoop is getting bigger.

In times of multiple cable lengths, the merging cable breaks up into sprats of parts (segments), as they do not connect with each other, but they save the same practice (Fig. 7.8). The maximum part of the string is overwhelmed when it is tied, like before. Obviously, it doesn’t measure the whole network, but allows for the correct distribution of subscribers by concentrators to save a significant part of the functions of the poor network.

Dekіlka concentrators can be constructively combined into a group, cluster (cluster), in the middle of which subscribers are also connected in the ring. Clustering allows you to increase the number of subscribers connected to one center, for example, up to 16 (for example, a cluster includes two hubs).

Rice. 7.7. Zgortannya kіltsya with poshkodzhennі cable

Rice. 7.8. Collapse of the ring with multiple cable failures

As the medium of transmission in the IBM Token-Ring line, a twisted pair of unscreened (UTP) and screened (STP) pairs were interlocked, and then there were options for equipment for a coaxial cable, as well as for a fiber optic cable in the FDDI standard.

Main technical characteristics classic version of Token-Ring:

• maximum number of hubs type IBM 8228 MAU - 12;
• the maximum number of subscribers at the Merezha is 96;
• the maximum length of the cable between the subscriber and the concentrator is 45 meters;
• maximum cable length between concentrators - 45 m;
• the maximum length of the cable, which is connected to the concentrators - 120 meters;
• speed of data transmission – 4 Mb/s and 16 Mb/s.

The necessary characteristics can be seen up to the point where the odds of non-screened twists of the bet are reversed. Even though the middle of the transmission is victorious, the characteristics of the border can be changed. For example, with a different screened twisted bet (STP), the number of subscribers can be increased to 260 (replacement 96), the length of the cable - up to 100 meters (replacement 45), the number of concentrators - up to 33, and the total number of concentrators - up to 20 concentrators meters Fiber optic cable allows you to extend the length of the cable up to two kilometers.

For transmission in the Token-Ring, a biphasic code is required (more precisely, this option with a binding transition at the center of the bit interval). As in the be-yakіy zirkopodіbnіbnіy topologii, zhdnih dodatkovyh zahodo elektricheskogo uzhodzhennia that zіrkopodіbnіy zemlіnії іn't nebіbіl. Uzgodzhennya vykonuetsya equipment mesh adapters and concentrators.

For the connection of Token-Ring cables, RJ-45 roses are used (for non-screened twisted bets), as well as MIC and DB9P. Conducting at the cable, one-time contacts of roses are connected (so that straight cables are called).

Merezha Token-Ring in the classic version comes with Ethernet merezha both for the allowable size and for the maximum number of subscribers. Depending on the speed of transmission, then in Denmark there are versions of Token-Ring for 100 Mb/s (High Speed ​​Token-Ring, HSTR) and 1000 Mb/s (Gigabit Token-Ring). Companies that promote Token-Ring (among them IBM, Olicom, Madge) should not try to think of us as their own, looking at it as a good competitor to Ethernet.

In pairs with Ethernet equipment, Token-Ring equipment is much more expensive, because the folding method of managing the exchange is victorious, and Token-Ring does not have such a wide width.

However, on the Ethernet interface, Token-Ring networks are much more likely to have a high profitability rate (more than 30-40%) and guarantee an hour of access. It is necessary, for example, at the borders of a common confession, in some obscurity, the reaction to the outward weather can lead to serious accidents.

The Token-Ring network uses a classic token access method, so that a token constantly circulates around the ring, so that subscribers can receive their data packets (div. Fig. 7.8). It is important to note the importance of the number of links, as the number of conflicts, but also the shortcomings, the need to control the integrity of the marker and the staleness of the function of the link to the skin subscriber (in case of malfunctions, the subscriber is switched on).

Token-Ring packet transmission time limit 10 ms. For the maximum number of subscribers 260, the last cycle of the warehouse operation is 260 x 10 ms = 2.6 s. In one hour, 260 subscribers will be able to transfer their packets (so, obviously, they can transfer). For tsey hour vіlny marker obov'yazkovo didde to the skin subscriber. This interval is the upper time limit for Token-Ring access.

Leather subscriber of the wire (yogo wire adapter) can be installed upcoming functions:

• the manifestation of pardons of the transfer;
• control of change of measures (renewal of measures at the exit from the operation of that subscriber, which is transferred to him in the country);
• control of the number of timchasovyh spіvvіdnoshen, adopted by the merezhі.

The number of functions is great, and it makes the equipment of the lace adapter more expensive.

To control the integrity of the marker in the measure, one of the subscribers is victorious (the so-called active monitor). When this is done, the equipment is not disturbed by anything in the decision, but yoga software follow timchasovym spіvvіdnoshnymi at merezhі i form a marker at different times.

The active monitor has the following functions:

• launches a marker on the cob of the robot in the ring when it is signed;
• regularly (every 7 s) inform about your presence with a special key package (AMP - Active Monitor Present);
• see a package from the ring, which is not seen by the subscriber, which he sent;
• follow the allowable hour of packet transmission.

The active monitor is selected at the initialization of the link, it can be a computer of the link, and then the subscriber will sound the first inclusion in the link. The subscriber, having become an active monitor, includes his buffer (existing register) in the measure, which guarantees that the marker will be placed in the ring at the minimum limit of the ring. The size of the buffer is 24 bits for a speed of 4 Mb/s and 32 bits for a speed of 16 Mb/s.

The skin of the subscriber is constantly stitched, like an active monitor, he is watching his own shoes. If the active monitor needs to go out of tune, then a special mechanism is activated, for which all other subscribers (spare, backup monitors) accept decisions about the recognition of a new active monitor. For this subscriber, having detected an active monitor failure, transmits a packet along the ring, which manages (token request packet) with his MAC address. The skin of the next subscriber is equal to the MAC address from the packet with the control. As a rule, the address is changed, the vin is transferred to the package, it was given without change. If it's more, then I'll put the vin in the packet with my MAC address. The active monitor will be the subscriber, which value of the MAC address is higher, lower for the others (it is the responsibility of three people to take back the packet with their MAC address). A sign of the exit from the operation of the active monitor є nevykonnannya him one of the overridden functions.

The token-ring marker is a packet that contains a total of three bytes (Fig. 7.9): the start delimiter byte (SD - Start Delimiter), the access control byte (AC - Access Control) and the end delimiter byte (ED - End Delimiter). All three bytes also enter the warehouse of the information package, but the truth is, the functions in the marker and in the package are little different.

Pochatkovy and last splitters are not just a sequence of zeros and ones, but signals of a special kind. The price was broken so that the distributors could not confuse with the smaller bytes of the packets.

Rice. 7.9. Token-Ring merge marker format

Cob splitter SD should be replaced with non-standard bit intervals (Fig. 7.10). Two, which are denoted by J, is a low value for a signal with a long bit interval. The other two bits that are designated are the highest value of the signal with the duration of the entire bit interval. Understandably, such failures in synchronization are easily detected by a trick. The battles J and K can by no means be shared among the battles of core information.

Rice. 7.10. Cob (SD) and end (ED) formats

Kіntsevy rasdіlnik ED is also a place for chotiri bits of a special type (two bits J and two bits K), as well as two single bits. Ale, moreover, before the new one enters and two informational bits, which may be more sensible at the warehouse of the information package:

• Bit I (Intermediate) is a sign of an intermediate package (1 is given to the first one in a lancet or an intermediate package, 0 - to the rest in a lancet or a single package).
• Bit E (Error) is a sign of a pronounced pardon (0 if pardons are valid, 1 - if they are).

Access control byte (AC - Access Control) divided into four fields (Fig. 7.11): priority field (three bits), marker bit, monitor bit, and reservation field (three bits).

Rice. 7.11. Byte format

The priority bit (field) allows the subscriber to give priority to his packets or to the marker (priority can be from 0 to 7, with 7 being the highest priority, and 0 being the lowest). The subscriber can come to the marker with his own package only if his own priority (priority of his packages) is the same as the priority of the marker.

The bit of the marker determines the number of times a packet arrives to the marker (one matches the marker without a packet, zero - to the marker with a packet). Monitor bit, set to one, check that the token is transmitted by the active monitor.

Reservation bits (field) allow the subscriber to reserve his right to bury the land far away in order to take up the service. If the priority of the subscriber (priority of one packet) is greater, the lower the value of the reservation field is, you can write down your own priority instead. After bypassing the ring, the reservation field will record the highest priority for all subscribers. Instead of a reservation field similar to that of a priority field, let's talk about future priority.

As a result, choosing the priority of the reservation ensures that less subscribers can access the media, as they can send transmission packets with the highest priority. Lesser priority packages will be served only after the selection of more priority packages.

The format of the information package (frame) Token-Ring is shown in fig. 7.12. The number of mail and end distributors, as well as the access control byte for which package is also included in the package control byte, the address of the receiving machine and the transmission, data, the checksum and the bytes of the package.

Rice. 7.12. Packet (frame) format of Token-Ring (more than one field is given in bytes)

Assignment of the field of the packet (frame).

• Cob splitter (SD) is a sign of the ear of the package, the format is the same as in the marker.
• The byte passed by access (AC) has the same format as the token.
• Byte keruvannya packet (FC - Frame Control) determines the type of packet (frame).
• The six-byte MAC address of the master and the host of the packet may have a standard format, descriptions in Lecture 4.
• Data field (Data) includes data that is transmitted (in the information package) or information for managing the exchange (in the same package).
• The checksum field (FCS - Frame Check Sequence) is a 32-bit cyclic checksum package (CRC).
• Ending retailer (ED), as and markers indicating the end of the package. In addition, we will determine whether this package is interim or concluded with the sequence of packages that are being transmitted, and also to avenge the sign of the pardon of the package (Div. Fig. 7.10).
• The byte of the packet (FS - Frame Status) will talk about those that were received with this packet: what will be accepted by the receiver (tobto, what is the receiver from the given address) and copied to the riddle of the receiver. The official of the package recognizes that the package is recognized for recognition and without pardon, otherwise it is required to transfer it again.

It should be noted that a larger allowable amount of data in one packet in a paired Ethernet network can become a critical factor for increasing the productivity of the network. Theoretically, for transfer speeds of 16 Mb/s and 100 Mb/s, the data field size can reach 18 KB, which is when transferring large data data. In addition, the 4 Mb/s security of the Token-Ring token access method often provides more actual transmission security than the Ethernet (10 Mb/s). Particularly noteworthy is the success of Token-Ring with great adventures(more than 30-40%), because in this case the CSMA/CD method has a lot of time to eliminate repeated conflicts.

The subscriber, who wants to send a packet, checks for the arrival of a valid marker and sips it. The zahopleniy marker turns into a frame of the information package. Then the subscriber sends an information package at the end of the bank and checks for the next turn. After the next wine, the marker is changed and I send it again to the border.

Token-Ring Merge In Token-Ring Merge, a special packet can be transmitted, as required, to abort the transmission (Abort). Vіn may be inscriptions at some time and in some place of the flow of data. The package is made up of two one-byte fields - a mail (SD) and an end (ED) distribution in the described format.

Well, the current version of Token-Ring (16 Mb/s and more) has the title of the method of early token formation (ETR - Early Token Release). Vіn allows the unproductive vineyard to vanish, until the package of data turns around the ring to its owner.

The ETR method is built up to the fact that immediately after the transmission of a packet received to the marker, whether any subscriber sees a new marker in the boundary. Other subscribers can start transferring their packets once the packet of the forward subscriber is finished, without checking until they complete the round trip of the whole chain. As a result, you can have a bunch of bags in one hour, but always there will be no more than one free marker. This conveyor is especially effective for long lines, which can mean a lot of delay.

When the subscriber is connected to the concentrator, the VIN is connected to the autonomous self-testing procedure and the cable is tested (at the end of the VIN, the VIN is still not turned on, because there is no signal from the phantom stream). The subscriber sends himself a series of packets and checks the correctness of their passage (going in without intermediary connection with the going out by the TCU, as shown in Fig. 7.4). After that, the subscriber turns on himself in the ring, overpowering the phantom strum. At the moment of inclusion, the package, which is being transferred across the ring, may be zipped. Let the subscriber set up synchronization and check the presence of the active monitor. Since there is no active monitor, the subscriber is rewarded for the right to become one. Then the subscriber checks the uniqueness of his/her address in the country and collects information about other subscribers. If you become a full-fledged participant in the exchange through the fence.

At the process of exchanging the skin, the subscriber is followed for the reference of the forward subscriber (according to the bill). As soon as the vin suspects the identity of the forward subscriber, the vin starts the procedure for automatic renewal of the ring. A special package (buoy) to tell the forward subscriber about the need to conduct a self-test and, possibly, turn it on in the ring.

The Token-Ring Merezha has also transferred a variety of bridges and commutators. The stench zastosovutsya for the subdivision of the great kіltsya on the kіlka of the kіltsev segments, like you may be able to exchange packages between yourself. This allows you to reduce the pressure on the skin segment and increase the hour that the skin subscriber hopes.

As a result, it is possible to form a separate ring, so that the connection of several ring segments in one great main ring (Fig. 7.13) or a mirror-ring structure with a central commutator, up to a connection of ring segments (Fig. 7.14).

Rice. 7.13. Consolidation of segments in the main ring behind additional bridges

Rice. 7.14. Consolidation of segments with a central switch

Merezha Arcnet (or ARCnet in English Attached Resource Computer Net, merezha computer z'ednah resursiv) is one of the oldest merezh. Vaughn was broken up by the Datapoint Corporation back in 1977. International standards on the borders of the day, although she herself is vvazhaetsya as the ancestor of the method of marker access. Regardless of the current standards, until recently (1980 - 1990) the Arcnet network was popular, and seriously competed with Ethernet. A large number of companies (for example, Datapoint, Standard Microsystems, Xircom, etc.) have manufactured equipment for this type of merchandise. But at the same time, the versatility of the Arcnet hardware is practically pinned down.

Among the main advantages of Arcnet and Ethernet pairing are the low access time, the high reliability of the connection, the ease of diagnostics, and also the low availability of adapters. To the most small amounts, one can see the low speed of transmission of information (2.5 Mb/s), the addressing system and the format of the packet.

For transmission in Arcnet measure, it is necessary to complete a logical code, for which a logical unit has two pulses over a bit interval, and a logical zero has one pulse. Obviously, this code, which is self-synchronizing, which means more cable bandwidth, lower Manchester.

As the medium of transmission of the wire, a coaxial cable with a flexible support of 93 Ohm is used, for example, brand RG-62A/U. Variants with a twisted pair (screened and non-screened) did not have a wide width. There were proponations and options on fiber optic cable, but the stench also did not turn Arcnet.

Like the topology of the Arcnet network, the classic bus (Arcnet-BUS), as well as the passive star (Arcnet-STAR). Concentrators (habi) are found at the vicory. It is possible to connect for additional concentrators of bus and mirror segments in a tree-like topology (like in Ethernet). The smut is free-flowing - the topology is not guilty of closed stakes (depends). One more exchange: the number of segments, joined by the last lancet for additional concentrators, is not guilty of revisiting the three.

Hubs are of two types:

• Active concentrators (inspire the shape of the signals and strengthen them). The number of ports - from 4 to 64. Active concentrators can be connected to each other (cascade).
• Passive concentrators (simply suppress signals that come without power). The number of ports is 4. Passive concentrators are not able to connect with each other. The stench may cause more active hubs and/or lesser adapters.

Bus segments can only be connected to active hubs.

Merezhev adapters are also available in two types:

• High-impedance (Bus), recognized for higher power in bus segments:
• Low impedance (Star), recognized for vikoristannya in a passive star.

Low-impedance adapters are designed for high-impedance types, so that the stench can be removed from your warehouse with a narrow 93-ohm terminator. With їх zastosuvanni zovnіshnє uzgodzhennia is not needed. In low-impedance bus segments, adapters can be used as the end of the bus. High-impedance adapters will interfere with older 93-ohm terminators. Deyakі merezhі adapters may be able to switch from a high-impedance mill to a low-impedance one, stinks can work both in tires and in the air.

In this way, the topology of the Arcnet network can look like this (Figure 7.15).

Rice. 7.15. Topology of an Arcnet network to a bus type (B - adapters for robotic bus, S - adapters for robotic mirror)

The main technical characteristics of the Arcnet mesh are offensive.

• Transmission medium - coaxial cable, twisted pair.
• The maximum length of the fence is 6 kilometers.
• The maximum cable length from the subscriber to the passive hub is 30 meters.
• The maximum cable length from the subscriber to the active hub is 600 meters.
• The maximum cable length between active and passive hubs is 30 meters.
• The maximum cable length between active hubs is 600 meters.
• Maximum number Merezha subscribers - 255.
• The maximum number of subscribers on the bus segment is 8.
• The minimum distance between subscribers at the bus is 1 meter.
• The maximum length of the tire segment is 300 meters.
• Transmission speed - 2.5 Mbit / s.

When folding folding topologies, it is necessary to make sure that the faucet of rozpovsyudzhennya signals at the border between subscribers does not exceed 30 μs. The maximum attenuation of the signal in the cable at a frequency of 5 MHz cannot exceed 11 dB.

In the Arcnet measure, the token access method (method of transfer of rights) is distinguished, but in some cases it is similar in the Token-Ring measure. The closest method to that, which is the transfer of the IEEE 802.4 standard. The sequence of subscribers for this method:

1. The subscriber, who wants to transmit, checks for the arrival of the marker.

2. Having removed the token, you will be asked to send information to the receiving subscriber (requesting whether to accept this packet).

3. Receptionist, after taking the request, overpowered (confirming his readiness).

4. After confirming readiness, the subscriber-transmitter overrides his package.

5. After rejecting the package, accept the force to confirm the receipt of the package.

6. The transmitter, having acknowledged the receipt of the packet, terminates its call session. The next token is transferred to the next subscriber in the order in which the address is changed.

In this manner, at each moment the package is transferred only to one, if there is a sense of readiness to accept yoga. This is a signifi- cant increase in the reliability of the transmission.

So, just like the Token-Ring option, Arcnet conflicts are turned off for the most part. As if it were a marker on a link, Arcnet does a good job of guaranteeing the value of an hour for access to a link (to Ethernet). The last hour of bypassing all subscribers becomes 840 ms as a marker. Obviously, this very interval sets the upper time interval for access to the border.

The marker is formed by a special subscriber - the controller of the measure. It is a subscriber with a minimum (zero) address.

If the subscriber does not remove the selected marker with a stretch of 840 ms, he sends a long bit sequence in the measure (for a guaranteed reduction of the zipped old marker). After that, a procedure for monitoring the recognition of a new controller (if necessary) is carried out.

Expand the Arcnet package to 0.5 KB. This data field also includes 8-bit send and receive addresses and a 16-bit cyclic checksum (CRC). Such a small size of the package does not seem to be worthwhile due to the high exchange rate in the measure.

Arcnet tier adapters are modified as adapters in other tiers, which are necessary for additional jumpers, or you can set the jumper at the same tier address (all of them can be 255, so the rest, 256 addresses are locked in the tier for wide traffic mode). The control over the uniqueness of the skin address of the merezha is imposed on the koristuvachіv merezhі. The connection of new subscribers is becoming when we do it foldable, it is necessary to set the keys to that address, as it has not yet been victorious. Selecting an 8-bit address format between the allowable number of subscribers in the merezhі - 255, which may be insufficient great companies.

As a result, everything has been brought to a practical new level of Arcnet. We based the options for the Arcnet network, the security of the transfer rate of 20 Mb/s, but the stench took a wide width.

Articles before reading:

Lecture 6: Standard Ethernet/Fast Ethernet Network Segments