Научная статья на тему 'Gigabit Ethernet in standard telecommunications networks'

Gigabit Ethernet in standard telecommunications networks Текст научной статьи по специальности «Строительство и архитектура»

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Ключевые слова
COMMUNICATION CHANNELS / HIGH SPEED / BANDWIDTH / FIBER OPTIC CABLE / TWISTED PAIR

Аннотация научной статьи по строительству и архитектуре, автор научной работы — Lojichevskaya V.Y., Svetlichnaya N.O.

The work deals with the technical possibilities of the standard telecommunications networks for mass introducing high-speed Ethernet, as well as prospects of the Ethernet technology development.

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Текст научной работы на тему «Gigabit Ethernet in standard telecommunications networks»

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Gigabit ethernet in standard telecommunications networks

The work deals with the technical possibilities of the standard telecommunications networks for mass introducing high-speed Ethernet, as well as prospects of the Ethernet technology development.

Keywords: Communication channels, high speed, bandwidth, fiber optic cable, twisted pair.

Lojichevskaya V.Y., SveHichnaya N.O.,

North-Caucasian branch

of the Moscow technical university

relationship and informatics

In the modern telecommunications networks various advanced technologies find their wide application, among them Ethernet, Token Ring, FDDI and others. The most popular network technology is Ethernet. Today the number of networks based on this technology is about 5 millions, and the number of computers with built-in network adapters is more than 50 millions. The first experimental Ethernet network was realized by the company Xerox in 1975. The Ethernet technology based on coaxial cable was adopted as a standard by DEC, Intel and Xerox in 1980. This version was called Ethernet DIX. The IEEE 802.3 standard was developed and in spite of some improvements it is much alike the first one.

FastEthernet Alliance, a non-profit organization established in 1992, was in charge to develop new high-speed standards for the technology. Its further works resulted in development of several complementary standards in the few following years. The appearance of the IEEE 802.3ab standard has become a stimulus for mass integration of gigabit Ethernet in the local area networks, as it did not need any changes in the cable infrastructure of the network. Besides the optical solution for gigabit Ethernet is rather costly and it is only used to build trunks and to connect remote local networks.

The first problem in realizing the 1Gb/s speed consists in providing a suitable diameter of the network (distance between two remotest computers) when working in a half-duplex mode. The reason is that the maximum diameter of the network must not exceed 25 meters in order to handle collisions successively. Besides the change of MAC- level, the achievement of gigabit speed has become possible due to substantial modification of the data presentation (coding) technology while transferring data along a twisted pair. To obtain a gigabit communication speed it is necessary to transfer data through four pairs simultaneously. To obtain a general trans-

mission speed of 1Gb/s, it is necessary to have a 250 MB/s speed for each pair. Taking into account that the maximum modulation speed for a 5-category cable is of 125 MHz (baud speed), information speed of 250 Mb/s can only be achieved under the condition that at each discrete state of a signal two information bits are to be coded.

Speaking about construction of gigabit communication channels, one should remember a number of essential limits. First of all, a server, which is supposed to include a gigabit network adapter, must have a 64-bit and 66-MHz PCI bus. As the bandwidth of the common 32-bit/33-MHz PCI bus is not enough to realize the whole potential of the gigabit network adapter. That is why the majority of the server gigabit network adapters has a 64-bit/66-MHz PCI-interface. However, even with the satisfied first condition a server with a very high performance is required. Otherwise the server would not be able to handle the gigabit traffic and the weak part of the network would be a processor subsystem of the server itself. If using a file-server, it will also need a powerful subsystem disk. If the possibilities of the disk and network subsystems are not balanced the server disk subsystem will become a weak part of the network. That is why high-performance disk RAID-massives are used in the fileservers.

While developing gigabit Ethernet and due to the appearance of entirely gigabit local networks the problem of networks balancing will inevitably arise. To settle this problem will be possible only if server connection channels and communication channels of network segments have a higher bandwidth, than connection channels of network nodes do. Another important condition is a higher speed, that is 10-gigabit Ethernet. But today it is too early to speak about a wide spreading of 10 Gigabit Ethernet. As the IEEE 802.3ae standard supposes

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the use of fiber optic communication channels while the use of copper pair was not planned at all. Several methods of transmitting through different types of fiber optic cables are specified. This enables to have a maximum distance of from 26 meters to 40 kilometers (depending on length of the laser beam and type of the used cable).

One can suppose that at least at first stage 10 Gigabit Ethernet will be employed to connect the groups of users and devices, and it will replace the fiber optic Gigabit Ethernet. First of all this includes wide area networks (WAN) and metropolitan area networks (MAN). In the local networks the new technology can find its application to connect data storage devices (NAS and SAN), as well as to organize the high-performance trunks. Connection of storages and their groups to the 10

Gigabit Ethernet network opens up wide possibilities to introduce the iSCSI protocol (SCSI over the Internet), as its bandwidth is two times higher than the maximum available through the Ultra320 SCSI interface. This is profitable not only for the carrying capacity of the interface, but also enables users to locate their storages outside an office, in some safety place.

Though the use of fiber optic cable to connect servers in local networks is rather seldom and possibilities of the processor and disk subsystems are not enough yet to realize the potential of 10 Gigabit Ethernet, we expect everything to change in the nearest future. And 10 Gigabit Ethernet technology will be in demand. That is why today 10 Gigabit Ethernet standard to work over twisted pair-based cable (10GBase-T) is being developed on base of IEEE. The IEEE research group has to estimate the

potentials to develop a standard permitting the data transmission at the speed of 10 GB/s through unshielded twisted pair (UTP) over distances up to 100 meters.

References

1 . Noise immunity and efficiency of transmission systems of information / under the editorship of A.G.Zyuko. M.: Radio and communication, 1985. 272 p.

2 . YarlikovM.S. Application of the Markov theory of non-linear filtering in the radio technician. M.: Sov.Radio, 1980. 360 p.

3. Hutortsev VV Metod of spline and gaussian approximation in the task of the adaptive filtration.//Radio engineering and electronics. 1990. T.35. No. 6. Pp.1217-1225.

Наукоёмкие технологии в космических исследованиях Земли № 2-2011

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