The gigabit ethernet network is operating at speed. Gigabit Ethernet

Many Russians have already learned the delights of Gigabit Ethernet. "

- Don't have Gigabit Ethernet yet? Then we go to you! We will tell you how to properly build a home network at gigabit speeds, which router to choose, what maximum speed can be achieved with the right equipment, and how much it will cost you.

Just a few years ago, Gigabit Ethernet technology was used only by telecom operators and large companies: in corporate networks, local networks, for transporting traffic over long distances, etc. Home subscribers did not even think about getting such speeds. But in 2012-2013, thanks to the improvement of "software" and "hardware", as well as the widest spread of Internet technologies, gigabit speeds have become more affordable and real for private users. Today, almost every metropolitan resident has the opportunity to build a network with Gigabit Ethernet support at home.

Many will ask: “Why have Internet at home with speeds of the order of 1 Gb / s at all? Is megabit Internet not enough for surfing websites, downloading movies and freezing up on social networks? "

We will answer in detail.

How a home user can use Gigabit Ethernet

Russian Internet users, as well as home Internet consumers around the world, are extremely active in using traffic. The volume of traffic consumed in the world is growing every month (not even a year already). A few years ago, we were happy with 1 Mbps, and even earlier, we were ready to download a movie all night to watch it later. Today, few people download videos at all, most of them watch directly online. Plus, thousands of users want HD quality and are willing to pay for it. And to watch and download videos in high quality, you need high-speed unlimited Internet.

Also, recently, torrent television is gaining popularity, allowing you to watch TV over the Internet, completely free of charge. Some users have already begun to abandon cable and satellite TV, others use torrent TV as a new interesting service and hope for its soon popularization. But in any case, for torrent-TV you need fast Internet, and even unlimited, otherwise this venture will cost more than a regular cable one.

A very important segment of high-speed broadband Internet consumers are gamers who play online. Today there are many online games for which young people (and not only young people) upgrade their PCs, pay for unlimited Internet with high connection speeds. Moreover, at the end of 2013 it is planned to release a new cult game Survarium from the creators of S.T.A.L.K.E.R. It will be an online game with free accounts. Considering how many Russians played the legendary S.T.A.L.K.E.R., Internet providers should prepare for a new influx of subscribers willing to pay for faster and more expensive Internet access. And users can start preparing now - and gigabit Internet can be the first step in this preparation.

In short, it is very easy to find the use of Gigabit Ethernet in a home network if you are an IT-advanced person and use modern technologies to the fullest.

Real Gigabit Ethernet Speed ​​- What's the Catch?

The phrase "gigabit internet" sounds loud, but are you really getting at least 1 Gbps? In fact, such a speed is achieved only under ideal conditions, it is unrealistic to get it at home, even if you install equipment that supports Gigabit Ethernet, configure everything as needed, order a gigabit package from your provider. Of course, you will get a speed 1,000 times higher than with 1 Mbit / s, because the same restrictions apply for the megabit Internet. But let's calculate what your Internet access speed will be.

We will count, using ordinary arithmetic, according to the "standard" approach. In addition, we will round off for simplicity: 1 kilobit = 1000 bits, not 1024 bits. In this case, 1 Gigabit is equal to 1000 megabits. But on a hard disk, information is not stored in bits, but in bytes - larger units. As everyone knows, 1 byte = 8 bits. For convenience, the amount of information and the speed of its transmission are usually considered in different units, and this often confuses the user, forcing him to expect more than it actually is.

Thus, the transfer rate of real files will be 8 times less than the provider says, since providers and speed testing programs count bits. Our 1 Gbps (1,000,000,000 bps) translates to 125,000,000 bytes (divided by 8). It turns out that 1 Gb / s = 125 MB / s.

But the problem is that the home user, due to various circumstances that do not always depend on him, actually gets only about 30% of the ideal 125 MB / s. That is, we already get about 37 MB / s. That's all that remains of 1 Gbps. But if you look at this figure in comparison with 1 Mbit / s, then we will still get 1,000 times faster Internet.

Home network equipment for Gigabit Ethernet

It is quite possible to create the conditions for a Gigabit Ethernet network at home today. Moreover, if you have a modern PC, then you will not need a very big re-equipment, and it will not cost as much as it might seem at first glance. The most important thing is to make sure that all of your primary devices are Gigabit Ethernet capable. After all, if at least one of them is not designed for such speeds, then in the end you will get a maximum of 100 Mbps.

If you want to achieve gigabit speeds, then you need the following equipment with support for 1 Gbps:

• a router that supports Gigabit Ethernet;
• network card (Ethernet adapter, network adapter);
• Network Controller;
• hub / switch;
• HDD;
• cables must be rated for 1 Gbps.

Each of the listed devices is an important link in the network; the final data transfer rate depends on each. So let's take a closer look at each of them.

Wi-Fi router. You need a gigabit router i.e. with Gigabit Ethernet support. These routers are somewhat more expensive than megabit ones, because they are designed for higher speeds. In principle, there are enough offers on the market under the brands Asus, TP-LINK, D-Link, etc. But base your choice on more than feature list, specs, and design. Be sure to check the forums (and at least 5) with reviews from real consumers to make sure that the router will work for a long time and reliably.

Network Card. This device can be integrated into the motherboard or stand-alone. The network adapter for a gigabit network must necessarily support Gigabit Ethernet. If your PC is more than 2-3 years old, then most likely the network card is outdated and does not support such high speeds. If you recently purchased a computer, then it is quite possible that you will not need to upgrade your network adapter. But in any case, check the characteristics of your specific network card for compatibility with the Gigabit Ethernet network.

Network Controller. If you are building a home network, then it is important that every computer on that network has a gigabit controller. Otherwise, only those PCs that have one will get sufficient speed. Like a network card, a network controller can be separate or integrated into the motherboard. Usually modern PCs have controllers that support 1 Gbps by default. So it is possible that you do not need to modify anything for Gigabit Ethernet.

Hub / Switch. It is one of the most expensive components in a home network. Often, it is already in the router. But check if it supports gigabit speeds. Important! A switch is more efficient than a hub because it routes data to only one specific port, and a hub to all of them. Using the switch, you can significantly save resource without spraying it over unnecessary ports.

HDD. It may seem strange to some, but the hard drive seriously affects the speed of Internet access. The fact is that it is the hard drive that sends data to the network controller, and how quickly you can transmit and receive data depends on their quality connection. It is desirable that the controller has a PCI Express (PCIe) interface, not a PCI one. And the hard drive must have a SATA connector, not IDE, since the latter supports too low speeds.

Network cable. Naturally, cable is an essential part of a home gigabit network. You can choose twisted pair Cat 5 and Cat 5e cables (used for laying telephone lines and local networks - they are enough for Gigabit Ethernet), or you can overpay a little and take Cat 6 cable (specially designed for Gigabit Ethernet and Fast Ethernet). The length of the twisted pair should be no more than 100 m, otherwise the signal begins to fade and the required speed of the Internet connection cannot be achieved. In addition, when placing cables in an apartment, pay attention to the fact that it is undesirable to lay them next to the power supply wires (read more about the reasons).

And the last important factor for organizing a home Gigabit Ethernet network is software. The operating system on the PC must be fresher. If it is Windows, then not earlier than Windows 2000 (and even then you have to dig into the settings). XP, Vista, Windows 7 versions support Gigabit Internet by default, so there shouldn't be any problems. With other operating systems, additional configuration may be necessary.

Top 5 Best Home Wi-Fi Routers
supporting Gigabit Ethernet, 2013

1. ASUS RT-N66U- an excellent model, powerful and reliable. Works simultaneously in two frequency bands - 2.4 and 5 GHz. The high speed of data transfer pleases - 900 Mbit / s is declared. Great for building a home Gigabit Ethernet network. But you need to reflash to improve performance and get rid of a number of problems that arise on native firmware. However, most routers require flashing immediately or shortly after purchase. The cost is about 4.5-5 thousand rubles.

2. D-Link DIR-825 - not a bad choice. This is a 2-band router, quite "stuffed". Working frequencies: 2.4 and 5 GHz; simultaneous use of both is available. This router has the best price-quality ratio on the market. Among the advantages is a wide distribution channel Wi-Fi (can pull up to 50 subscribers). From the point of view of users, the most noticeable disadvantage is the bright LED indication of the device, but this is more a matter of taste than the quality of the device. As for the firmware, you can leave the native one, but it is recommended to reflash to improve performance. Router price: about 3 thousand rubles.

3. TP-LINK TL-WDR4300 Is a very fast router, great for home networks. The manufacturer claims a maximum data transfer rate of 750 Mbps. One of the important advantages of this model over many others is the ability to simultaneously use two frequency bands: 2.4 and 5 GHz. Thanks to this, users can simultaneously connect to the Internet from phones, smartphones, and from a laptop, PC or tablet. Another plus of this model is that it comes with powerful enough antennas that allow you to distribute the Internet via Wi-Fi for more than 200 m. But in order for all this to function normally, it is better to change the firmware from the factory. Through a series of software manipulations, the device will perform much better. Model price: about 3 thousand rubles.

4. Zyxel Keenetic Giga is a decent router with several useful features. Its main disadvantage is that the router works only in one frequency range - 2.4 GHz. But at the same time, the speed is sufficient to watch IP-TV, use torrent networks (there is a built-in torrent client) and other "gluttonous" services. The Zyxel Keenetic Giga is equipped with powerful antennas, which allows you to create Wi-Fi networks (by the way, the device supports all Wi-Fi standards) with a long range. The router is quite simple to set up, but the firmware, like for most routers, will have to be changed. Another plus is that the device is relatively inexpensive - from 3 to 4 thousand rubles.

5. TP-LINK TL-WR1043ND - a fairly powerful and cheap gigabit router. However, it has several disadvantages. Firstly, it works only in the 2.4 GHz band, which is not very convenient. Secondly, it is more suitable for experienced users, since the native firmware, as in many cases, is not very good, and it can be difficult to reflash this model. But all this is more than offset by the reliability and power of this router. The maximum data transfer rate is 300 Mbps. The device works out its money, since the price of the model is only 2 thousand rubles.

I was in no rush to move my home network from 100 Mbps to 1 Gbps, which is rather strange to me since I am transferring a large amount of files over the network. However, when I spend money on upgrading my computer or infrastructure, I believe that I should immediately get a performance boost in the applications and games I run. Many users like to amuse themselves with a new video card, central processor and some kind of gadget. However, for some reason, networking equipment does not attract such enthusiasm. Indeed, it is difficult to invest the money earned in the network infrastructure instead of another technological birthday present.

However, my bandwidth requirements are very high, and at one point I realized that the infrastructure for 100 Mbps was no longer enough. All my home computers already have 1 Gbps integrated adapters (on motherboards), so I decided to take the price list of the nearest computer company and see what I would need to transfer my entire network infrastructure to 1 Gbps.

No, a home gigabit network is not that complicated at all.

I bought and installed all the hardware. I remember that it used to take about a minute and a half to copy a large file over a 100 Mbps network. After upgrading to 1 Gbps, the same file was copied in 40 seconds. The performance gains were nice, but I still didn't get the tenfold superiority that one would expect from comparing the 100 Mbps versus 1 Gbps bandwidth of the old and new networks.

What is the reason?

For a gigabit network, all parts of it must support 1 Gbps. For example, if you have gigabit network cards and corresponding cables installed, but the hub / switch only supports 100 Mbps, then the entire network will operate at 100 Mbps.

The first requirement is a network controller. It is best if each computer on the network is equipped with a gigabit network adapter (separate or integrated on the motherboard). This requirement is the easiest to meet, since most motherboard manufacturers have been integrating gigabit network controllers over the past couple of years.

The second requirement is that the network card must also support 1 Gbps. There is a common misconception that gigabit networks require Category 5e cable, but in fact even older Cat 5 cables support 1 Gbps. However, Cat 5e cables are superior in performance, so they are better suited for gigabit networks, especially if the cables are long enough. However, Cat 5e cables are still the cheapest today because the old Cat 5 standard is outdated. Newer and more expensive Cat 6 cables offer even better performance for gigabit networks. We'll compare the performance of Cat 5e vs Cat 6 cables later in this article.

The third and probably most expensive component in a gigabit network is a 1 Gbps hub / switch. Of course, it is better to use a switch (possibly paired with a router), since a hub or hub is not the most intelligent device that simply broadcasts all network data to all available ports, which leads to a large number of collisions and slows down network performance. If you need high performance, a gigabit switch is essential because it only redirects network data to the correct port, effectively increasing the speed of your network in comparison to a hub. A router usually contains a built-in switch (with multiple LAN ports) and also allows you to connect your home network to the Internet. Most home users understand the benefits of a router, so a gigabit router is an attractive option.

CONTENT

The modern world is increasingly becoming dependent on the volume and flow of information going in various directions via wires and without them. It all started a long time ago and with more primitive means than today's achievements of the digital world. But we do not intend to describe all the types and methods by which one person brought the necessary information to the consciousness of another. In this article, I would like to offer the reader a story about the not so long ago created and now successfully developing standard for transmitting digital information, which is called Ethernet.

The birth of the very idea and the Ethernet technology took place within the walls of the Xerox PARC corporation, along with other early developments in the same direction. The official date for the invention of Ethernet was May 22, 1973, when Robert Metcalfe wrote a memo for the head of PARC on the potential of Ethernet technology. However, it was patented only a few years later.

In 1979, Metcalfe left Xerox and founded 3Com, whose main focus was to promote computers and local area networks (LANs). With the support of such renowned companies as DEC, Intel and Xerox, the Ethernet standard (DIX) was developed. After its official publication on September 30, 1980, it began a rivalry with two large patented technologies - token ring and ARCNET, which were subsequently completely replaced, due to their lower efficiency and higher cost than Ethernet products.

Initially, according to the proposed standards (Ethernet v1.0 and Ethernet v2.0), they were going to use coaxial cable as a transmission medium, but later they had to abandon this technology and switch to using optical cables and twisted pair.

The main advantage in the early development of Ethernet technology was the method of access control. It implies multiple connections with carrier sense and collision detection (CSMA / CD, Carrier Sense Multiple Access with Collision Detection), the data transfer rate is 10 Mbps, the packet size is from 72 to 1526 bytes, it also describes the data encoding methods ... The limit value of workstations in one shared network segment is limited to 1024, but other smaller values ​​are possible if you set more stringent limits for the thin coaxial segment. But such a construction very soon became ineffective and was replaced in 1995 by the IEEE 802.3u Fast Ethernet standard with a speed of 100 Mbps, and later the IEEE 802.3z Gigabit Ethernet standard with a speed of 1000 Mbps was adopted. At the moment, 10 Gigabit Ethernet IEEE 802.3ae is already in full use, with a speed of 10,000 Mbit / s. In addition, we already have developments aimed at achieving a speed of 100,000 Mbit / s 100 Gigabit Ethernet, but first things first.

A very important position underlying the Ethernet standard is its frame format. However, there are quite a few options for it. Here is some of them:

Variant I is the firstborn and already out of use.

Ethernet Version 2 or Ethernet frame II, also called DIX (abbreviation of the first letters of the developers of DEC, Intel, Xerox) is the most common and is used to this day. Often used directly by the Internet Protocol.

Novell is an internal modification of IEEE 802.3 without LLC (Logical Link Control).

IEEE 802.2 LLC frame.

IEEE 802.2 LLC / SNAP frame.

In addition, an Ethernet frame can contain an IEEE 802.1Q tag to identify the VLAN to which it is addressed and an IEEE 802.1p tag to indicate priority.

Some Hewlett-Packard Ethernet cards used an IEEE 802.12 frame that conforms to the 100VG-AnyLAN standard.

For different frame types, there are also different formats and MTU values.

Functional elements of technologyGigabit Ethernet

Note that manufacturers of Ethernet cards and other devices mainly include support for several previous baud rate standards in their products. By default, using autosensing of speed and duplex, the card drivers themselves determine the optimal mode of operation for the connection between the two devices, but usually there is also a manual choice. So, buying a device with 10/100/1000 Ethernet port, we get the opportunity to work with 10BASE-T, 100BASE-TX, and 1000BASE-T technologies.

Here is the chronology of modifications Ethernet by dividing them by transmission rates.

First decisions:

Xerox Ethernet is the original technology, the speed of 3 Mbps, existed in two versions, Version 1 and Version 2, the frame format of the latest version is still widely used.

10BROAD36 - not widespread. One of the first standards to allow long distance work. Used broadband modulation technology similar to that used in cable modems. A coaxial cable was used as a data transmission medium.

1BASE5 - also known as StarLAN, was the first modification of Ethernet technology to use twisted pair cables. It worked at a speed of 1 Mbit / s, but did not find commercial use.

The more common and optimized for its time modifications of 10 Mbit / s Ethernet:

10BASE5, IEEE 802.3 (also called "Thick Ethernet") was the original development of a technology with a data transfer rate of 10 Mbps. The IEEE uses a 50 ohm coaxial cable (RG-8) with a maximum segment length of 500 meters.

10BASE2, IEEE 802.3a (called "Thin Ethernet") - uses RG-58 cable, with a maximum segment length of 200 meters. To connect computers to each other and connect the cable to the network card, you need a T-connector, and the cable must have a BNC connector. Terminators are required at each end. For many years this standard has been the main standard for Ethernet technology.

StarLAN 10 - The first design to use twisted pair cable for data transmission at 10 Mbps. Later, it evolved into the 10BASE-T standard.

10BASE-T, IEEE 802.3i - 4 twisted pair cables (two twisted pairs) of Category 3 or Category 5 are used for data transmission. The maximum segment length is 100 meters.

FOIRL - (acronym for Fiber-optic inter-repeater link). Basic standard for Ethernet technology using optical cable for data transmission. The maximum data transmission distance without repeater is 1 km.

10BASE-F, IEEE 802.3j - The main term for the 10 Mbit / s family of Eethernet standards using fiber optic cables up to 2 kilometers away: 10BASE-FL, 10BASE-FB, and 10BASE-FP. Of the above, only 10BASE-FL is widely used.

10BASE-FL (Fiber Link) - An improved version of the FOIRL standard. The improvement concerned an increase in the segment length up to 2 km.

10BASE-FB (Fiber Backbone) - Now an unused standard, it was intended for combining repeaters into a backbone.

• 10BASE-FP (Fiber Passive) - Passive star topology that does not require repeaters - developed but never implemented.

The most common and inexpensive choice at the time of writing Fast Ethernet (100 Mbps) ( Fast Ethernet):

100BASE-T - The main term for one of the three standards of 100 Mbit / s Ethernet, using twisted pair as the data transmission medium. Segment length up to 100 meters. Includes 100BASE-TX, 100BASE-T4 and 100BASE-T2.

100BASE-TX, IEEE 802.3u - The development of 10BASE-T technology, a star topology is used, a twisted pair cable of category 5 is used, which actually uses 2 pairs of conductors, the maximum data transfer rate is 100 Mbps.

100BASE-T4 - 100 Mbps Ethernet over Category 3 cable. All 4 pairs are used. Now it is practically not used. Data transmission is in half duplex mode.

100BASE-T2 - Not used. 100 Mbps Ethernet over Category 3 cable. Only 2 pairs are used. Full duplex transmission mode is supported, when signals propagate in opposite directions on each pair. The transmission speed in one direction is 50 Mbit / s.

100BASE-FX - 100 Mbps Ethernet over fiber optic cable. The maximum segment length is 400 meters in half duplex mode (for guaranteed collision detection) or 2 kilometers in full duplex mode over multimode fiber.

100BASE-LX - 100 Mbps Ethernet over fiber optic cable. The maximum segment length is 15 kilometers in full duplex mode over a pair of single-mode optical fibers at a wavelength of 1310 nm.

100BASE-LX WDM - 100 Mbps Ethernet over fiber optic cable. The maximum segment length is 15 kilometers in full duplex mode over one single-mode optical fiber at a wavelength of 1310 nm and 1550 nm. Interfaces are of two types, differ in the transmitter wavelength and are marked with either numbers (wavelength) or one Latin letter A (1310) or B (1550). Only paired interfaces can work in pairs, on the one hand a transmitter at 1310 nm, and on the other at 1550 nm.

Gigabit Ethernet

1000BASE-T, IEEE 802.3ab - 1 Gbps Ethernet standard. A twisted pair of category 5e or category 6 is used. All 4 pairs are involved in data transmission. The data transfer rate is 250 Mbps over one pair.

1000BASE-TX, - 1 Gbps Ethernet standard using only Category 6 twisted pair. Transmitting and receiving pairs are physically separated by two pairs in each direction, which greatly simplifies the design of transceiver devices. The data transfer rate is 500 Mbps over one pair. Practically not used.

1000Base-X is a generic term for Gigabit Ethernet technology with pluggable GBIC or SFP transceivers.

1000BASE-SX, IEEE 802.3z - 1 Gbps Ethernet technology uses lasers with an allowable radiation length within the range of 770-860 nm, transmitter radiation power in the range from -10 to 0 dBm with an ON / OFF ratio (signal / no signal) not less than 9 dB. Receiver sensitivity 17 dBm, receiver saturation 0 dBm. Using multimode fiber, the signal transmission range without repeater is up to 550 meters.

1000BASE-LX, IEEE 802.3z - 1 Gbps Ethernet technology uses lasers with an allowable radiation length within the range of 1270-1355 nm, transmitter radiation power in the range from 13.5 to 3 dBm, with an ON / OFF ratio (there is a signal / no signal) not less than 9 dB. Receiver sensitivity 19 dBm, receiver saturation 3 dBm. When using multimode fiber, the signal transmission range without a repeater is up to 550 meters. Optimized for long distance using single mode fiber (up to 40 km).

1000BASE-CX - Gigabit Ethernet technology for short distances (up to 25 meters), uses a special copper cable (Shielded Twisted Pair (STP)) with a characteristic impedance of 150 ohms. Replaced by 1000BASE-T standard, and is not used now.

1000BASE-LH (Long Haul) - 1 Gbps Ethernet technology, uses a single-mode optical cable, the signal transmission range without a repeater is up to 100 kilometers.

Standard	Cable type	Bandwidth (not worse), MHz * Km	Max. distance, m *
1000BASE-LX (1300 nm laser diode)	Singlemode fiber (9μm)
	Multimode fiber (50 μm)
	Multimode fiber (62.5 μm)
1000BASE-SX (850nm laser diode)	Multimode fiber (50 μm)
	Multimode fiber (62.5 μm)
	Multimode fiber (62.5 μm)
	Shielded Twisted Pair STP (150 OM)
* 1000BASE-SX and 1000BASE-LX standards assume full duplex mode ** Equipment of some manufacturers can provide a greater distance, optical segments without intermediate repeaters / amplifiers can reach 100 km.

Specifications of 1000Base-X standards

10 Gigabit Ethernet

Still quite expensive, but quite popular, the new 10 Gigabit Ethernet standard includes seven physical media standards for LAN, MAN and WAN. It is currently covered by the IEEE 802.3a amendment and should be included in the next revision of the IEEE 802.3 standard.

10GBASE-CX4 - 10 Gigabit Ethernet technology for short distances (up to 15 meters) using CX4 copper cable and InfiniBand connectors.

10GBASE-SR - 10 Gigabit Ethernet technology for short distances (up to 26 or 82 meters, depending on the cable type) using multimode fiber. It also supports distances up to 300 meters using new multimode fiber (2000 MHz / km).

10GBASE-LX4 - Uses wavelength division multiplexing to support distances from 240 to 300 meters over multimode fiber. Also supports distances up to 10 kilometers when using single-mode fiber.

10GBASE-LR and 10GBASE-ER - these standards support distances up to 10 and 40 kilometers, respectively.

10GBASE-SW, 10GBASE-LW, and 10GBASE-EW - These standards use a physical interface that is speed and data format compatible with the OC-192 / STM-64 SONET / SDH interface. They are similar to the 10GBASE-SR, 10GBASE-LR and 10GBASE-ER standards respectively, as they use the same cable types and transmission distances.

10GBASE-T, IEEE 802.3an-2006 - adopted in June 2006 after 4 years of development. Uses shielded twisted pair cable. Distances - up to 100 meters.

And finally, what do we know about 100-Gigabit Ethernet(100-GE), still a fairly crude, but quite popular technology.

In April 2007, after the meeting of the IEEE 802.3 committee in Ottawa, the Higher Speed ​​Study Group (HSSG) took an opinion on the technical approaches in the formation of optical and copper 100-GE channels. At this time, the 802.3ba working group has been finally formed to develop the 100-GE specification.

As in previous developments, the 100-GE standard will take into account not only the economic and technical feasibility of its implementation, but also their backward compatibility with existing systems. At this time, the need for such speeds has been undeniably proven by leading companies. Constantly growing volumes of personalized content, including when delivering videos from portals such as YouTube and other resources using IPTV and HDTV technologies. We should also mention video on demand. All this determines the need for 100 Gigabit Ethernet operators and service providers.

But against the background of a large selection of old and promising new technological approaches within the Ethernet group, we want to dwell in more detail on the technology, which today is only acquiring full-fledged mass use due to the decrease in the cost of its components. Gigabit Ethernet can fully support applications such as video streaming, video conferencing, and complex image transmission with increased bandwidth requirements. The benefits of higher transmission speeds in corporate and home networks are becoming more and more indisputable, with falling prices for equipment of this class.

Now the IEEE standard has received the maximum popularity. Adopted in June 1998, it was approved as IEEE 802.3z. But at first, only an optical cable was used as a transmission medium. With the approval of the addition of the 802.3ab standard during the following year, Category 5 unshielded twisted pair became the transmission medium.

Gigabit Ethernet is a direct descendant of Ethernet and Fast Ethernet, which have proven themselves well over nearly twenty years of history, maintaining their reliability and future-proofing. Along with the foreseen backward compatibility with previous solutions (the cable structure remains unchanged), it provides a theoretical throughput of 1000 Mbps, which is approximately equal to 120 Mb per second. It should be noted that such capabilities are practically equal to the speed of a 32-bit 33 MHz PCI bus. That is why gigabit adapters are available both for 32-bit PCI (33 and 66 MHz) and for 64-bit bus. Along with this increase in speed, Gigabit Ethernet inherited all previous Ethernet features such as frame format, CSMA / CD (Transmission Sensitive Collision Detection Multiple Access) technology, full duplex, etc. Although high speeds have made their own innovations, it is precisely in the inheritance of old standards that the huge advantage and popularity of Gigabit Ethernet lies. Of course, other solutions are now proposed, such as ATM and Fiber Channel, but here the main advantage for the end user is immediately lost. The transition to a different technology leads to a massive rework and re-equipment of enterprise networks, while Gigabit Ethernet will allow for a smooth increase in speed and not change the cabling. This approach allowed Ethernet technology to take a dominant place in the field of network technologies and conquer more than 80 percent of the world information transmission market.

The structure of building an Ethernet network with smooth transitions to higher data rates.

Initially, all Ethernet standards were developed using only an optical cable as a transmission medium - so Gigabit Ethernet received a 1000BASE-X interface. It is based on the Fiber Channel physical layer standard (a technology for interworking workstations, storage devices, and edge nodes). Since this technology had already been approved earlier, this borrowing greatly reduced the development time for the Gigabit Ethernet standard. 1000BASE-X

We, as well as a common man in the street, were more interested in 1000Base-CX in view of its operation on shielded twisted pair (STP "twinax") for short distances and 1000BASE-T for unshielded twisted pair of category 5. The main difference between 1000BASE-T and Fast Ethernet 100BASE- TX became that all four pairs were used (in 100BASE-TX only two were used). At the same time, each pair can transmit data at a speed of 250 Mbps. The standard provides full duplex transmission, with the flow on each pair being provided in two directions simultaneously. Due to strong interference during such transmission, it was technically much more difficult to implement gigabit transmission over twisted pair than in 100BASE-TX, which required the development of a special scrambled noise-immune transmission, as well as an intelligent node for recognizing and recovering a signal at reception. As a coding method in the 1000BASE-T standard, 5-level pulse-amplitude coding PAM-5 was used.

The criteria for choosing a cable have also become more stringent. To reduce interference, unidirectional transmission, return loss, delay and phase shift, Category 5e for unshielded twisted pair has been adopted.

Crimping cable for 1000BASE-T is performed according to one of the following schemes:

Straight-through cable.

Crossover cable.

Crimping diagrams of a cable for 1000BASE-T

The innovations also affected the level of the MAC-standard 1000BASE-T. In Ethernet networks, the maximum distance between stations (collision domain) is determined based on the minimum frame size (in the Ethernet IEEE 802.3 standard it was 64 bytes). The maximum segment length must be such that the transmitting station can detect a collision before the end of the frame transmission (the signal must have time to pass to the other end of the segment and return back). Accordingly, with an increase in the transmission rate, it is necessary either to increase the frame size, thereby increasing the minimum time for transmitting a frame, or to decrease the diameter of the collision domain.

When switching to Fast Ethernet, they used the second option and reduced the segment diameter. In Gigabit Ethernet, this was not acceptable. Indeed, in this case, the standard that inherited such components of Fast Ethernet as the minimum frame size, CSMA / CD and the time slot for collision detection will be able to work in collision domains with a diameter of no more than 20 meters. Therefore, it was proposed to increase the time for transmitting the minimum frame. Considering that for compatibility with previous Ethernet, the minimum frame size was left the same - 64 bytes, and an additional carrier extension field was added to the frame, which complements the frame to 512 bytes, but the field is not added in the case when the frame size is greater than 512 byte. Thus, the resulting minimum frame size turned out to be 512 bytes, the time for collision detection increased, and the segment diameter increased to the same 200 meters (in the case of 1000BASE-T). Symbols in the carrier extension field have no semantic meaning, the checksum is not calculated for them. When a frame is received, this field is discarded even at the MAC layer, so the higher layers continue to work with minimum frames of 64 bytes long.

But here too there were pitfalls. While the media expansion allowed for compatibility with previous standards, it wasted bandwidth. Loss can be as high as 448 bytes (512-64) per frame for short frames. Therefore, the 1000BASE-T standard was modernized - the concept of Packet Bursting was introduced. It allows you to use the expansion field much more effectively. And it works as follows: if the adapter or switch has several small frames that need to be sent, then the first of them is sent in the standard way, with the addition of an extension field up to 512 bytes. And all subsequent ones are sent in their original form (without the extension field), with a minimum interval of 96 bits between them. And, most importantly, this interframe gap is filled with media spread symbols. This happens until the total size of frames sent reaches the limit of 1518 bytes. Thus, the medium does not fall silent throughout the transmission of small frames, so a collision can occur only at the first stage, when transmitting the first correct small frame with a carrier expansion field (512 bytes in size). This mechanism can significantly improve network performance, especially under heavy loads, by reducing the likelihood of collisions.

But this was not enough. At first, Gigabit Ethernet only supported standard Ethernet frame sizes, from a minimum of 64 (padded to 512) to a maximum of 1518 bytes. Of these, 18 bytes are occupied by the standard service header, and for data there are from 46 to 1500 bytes, respectively. But even a 1500 byte data packet is too small in the case of a gigabit network. Especially for servers transferring large amounts of data. Let's count a little. To transfer a 1 gigabyte file over an unloaded Fast Ethernet network, the server processes 8200 packets / sec and takes at least 11 seconds to do this. In this case, it will take about 10 percent of the time for a 200 MIPS computer to handle interrupts alone. After all, the central processor must process (calculate the checksum, transfer data to memory) each packet that arrives.

Speed	10 Mbps		100 Mbps		1000 Mbps
Frame size
Frames / sec
Data transfer rate, Mbps
Interval between frames, μs

Ethernet transmission characteristics.

In gigabit networks, the situation is even worse - the load on the processor increases by about an order of magnitude due to the reduction in the time interval between frames and, accordingly, interrupt requests to the processor. Table 1 shows that even under the best conditions (using frames of the maximum size), the frames are spaced from each other by a time interval not exceeding 12 μs. In the case of using smaller frames, this time interval only decreases. Therefore, in gigabit networks, the bottleneck, oddly enough, was the stage of processing frames by the processor. Therefore, at the dawn of the formation of Gigabit Ethernet, the actual transfer rates were far from the theoretical maximum - the processors simply could not cope with the load.

The obvious way out of this situation is the following:

increasing the time interval between frames;

shifting part of the load of processing frames from the central processor to the network adapter itself.

Both methods are currently implemented. In 1999, it was proposed to increase the packet size. Such packets were called Jumbo Frames, and their size could be from 1518 to 9018 bytes (currently, equipment from some manufacturers also supports large giga frame sizes). Jumbo Frames allowed to reduce the load on the central processor up to 6 times (proportional to its size) and, thus, significantly increase performance. For example, the maximum Jumbo Frame packet of 9018 bytes, in addition to the 18-byte header, contains 9000 bytes for data, which corresponds to six standard maximum Ethernet frames. The gain in performance is achieved not due to getting rid of several service headers (the traffic from their transmission does not exceed several percent of the total bandwidth), but due to the reduction in the time spent on processing such a frame. More precisely, the time to process a frame remains the same, but instead of several small frames, each of which would require N processor cycles and one interrupt, we process only one, larger frame.

The rather rapidly developing world of information processing speed provides faster and more inexpensive solutions for the use of special hardware to remove part of the traffic processing load from the central processor. Buffering technology is also used to interrupt the processor to process multiple frames at once. At this time, Gigabit Ethernet technology is becoming more and more available for use at home, which will directly interest the common user. Faster access to home resources will provide high-quality viewing of high-definition video, take less time to redistribute information and, finally, will allow live encoding of video streams to network drives.

In the preparation of the article, resource materials were used http://www.ixbt.com/ andhttp://www.wikipedia.org/.

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Gigabit Ethernet

Now there is a lot of talk about the time to massively switch to gigabit speeds when connecting end users of local networks, and again the question is raised about the justification and progressiveness of solutions "fiber to the workplace", "fiber to home", etc. In this regard, this article, describing the standards not only for copper, but also mainly for fiber-optic GigE interfaces, will be quite appropriate and timely.

Gigabit Ethernet architecture

Figure 1 shows the structure of the Gigabit Ethernet layers. As in the Fast Ethernet standard, in Gigabit Ethernet there is no universal signal coding scheme that would be ideal for all physical interfaces - so, on the one hand, 1000Base-LX / SX / CX standards use 8B / 10B coding, and on the other On the other hand, for the 1000Base-T standard, a special extended line code TX / T2 is used. The encoding function is performed by the PCS encoding sublayer located below the independent GMII interface.

Rice. 1. Layer structure of Gigabit Ethernet standard, GII interface and Gigabit Ethernet transceiver

GMII interface. The Gigabit Media Independent Interface (GMII) provides interoperability between the MAC layer and the physical layer. The GMII interface is an extension of the MII interface and can support speeds of 10, 100 and 1000 Mbps. It has a separate 8-bit receiver and transmitter, and can support both half-duplex and full-duplex modes. In addition, the GMII interface carries one clock signal, and two line status signals - the first (in the ON state) indicates the presence of a carrier, and the second (in the ON state) indicates the absence of collisions - and several other signal channels. and food. The transceiver module, covering the physical layer and providing one of the physical media-dependent interfaces, can connect, for example, to a Gigabit Ethernet switch via a GMII interface.

PCS physical coding sublayer. When connecting 1000Base-X interfaces, the PCS sublayer uses 8B10B block redundant coding, borrowed from the ANSI X3T11 Fiber Channel standard. Similar to the considered FDDI standard, only on the basis of a more complex code table, every 8 input bits intended for transmission to a remote node are converted into 10-bit symbols (code groups). In addition, there are special 10-bit control characters in the output serial stream. An example of control characters are characters used to expand media (padding a Gigabit Ethernet frame to its minimum size of 512 bytes). When connecting the 1000Base-T interface, the PCS sublayer implements a special noise-immune coding to ensure transmission over UTP Cat.5 twisted pair at a distance of up to 100 meters - the TX / T2 line code developed by Level One Communications.

Two line status signals - carrier presence signal and collision absence signal - are generated by this sublevel.

Sublevels PMA and PMD. The physical layer of Gigabit Ethernet uses multiple interfaces, including traditional Category 5 twisted pair, multimode and singlemode fiber. The PMA sublayer converts the parallel character stream from the PCS to a serial stream, and also converts (parallelizes) the incoming serial stream from the PMD. The PMD sublayer defines the optical / electrical characteristics of physical signals for different environments. In total, 4 different types of physical media interfaces are defined, which are reflected in the specification of the 802.3z (1000Base-X) and 802.3ab (1000Base-T) standards, (Fig. 2).

Rice. 2. Physical interfaces of the Gigabit Ethernet standard

1000Base-X interface

The 1000Base-X interface is based on the Fiber Channel physical layer standard. Fiber Channel is a technology that interconnects workstations, supercomputers, storage devices, and edge nodes. Fiber Channel has a 4-tier architecture. The two lower layers FC-0 (interfaces and media) and FC-1 (encode / decode) have been moved to Gigabit Ethernet. Since Fiber Channel is an approved technology, this move has greatly reduced the development time for the original Gigabit Ethernet standard.

The 8B / 10B block code is similar to the 4B / 5B code used in the FDDI standard. However, the 4B / 5B code was rejected in Fiber Channel because the code does not provide DC balance. The imbalance can potentially lead to data-dependent heating of the laser diodes, as the transmitter can transmit more "1" (radiation) bits than "0" (no radiation), which can cause additional errors at high baud rates.

1000Base-X is subdivided into three physical interfaces, the main characteristics of which are as follows:

The 1000Base-SX interface detects lasers with an allowable radiation length within the range of 770-860 nm, the transmitter radiation power in the range from -10 to 0 dBm, with an ON / OFF ratio (signal / no signal) not less than 9 dB. Receiver sensitivity -17 dBm, receiver saturation 0 dBm;

The 1000Base-LX interface detects lasers with an allowable radiation length within the 1270-1355 nm range, the transmitter radiation power in the range from -13.5 to -3 dBm, with an ON / OFF ratio (there is a signal / no signal) not less than 9 dB. Receiver sensitivity -19 dBm, receiver saturation -3 dBm;

1000Base-CX shielded twisted pair (STP "twinax") over short distances.

For reference, Table 1 shows the main characteristics of optical transceiver modules manufactured by Hewlett Packard for standard interfaces 1000Base-SX (model HFBR-5305, = 850 nm) and 1000Base-LX (model HFCT-5305, = 1300 nm).

Table 1. Technical characteristics of optical Gigabit Ethernet transceivers

The supported distances for 1000Base-X standards are shown in Table 2.

Table 2. Technical characteristics of optical Gigabit Ethernet transceivers

When encoding 8B / 10B, the bit rate in the optical line is 1250 bps. This means that the bandwidth of the allowed cable length must be greater than 625 MHz. From table. 2 shows that this criterion is met for lines 2-6. Due to the high transmission speed of Gigabit Ethernet, care should be taken when constructing long segments. Single-mode fiber is clearly preferred. In this case, the characteristics of optical transceivers can be significantly higher. For example, NBase manufactures switches with Gigabit Ethernet ports that provide distances up to 40 km over single-mode fiber without retransmission (narrow-spectrum DFB lasers operating at 1550 nm are used).

features of using multimode fiber

There are a huge number of corporate networks in the world based on multimode fiber-optic cable, with 62.5 / 125 and 50/125 fibers. Therefore, it is natural that even at the stage of the formation of the Gigabit Ethernet standard, the problem arose of adapting this technology for use in existing multimode cable systems. In the course of research on the development of the 1000Base-SX and 1000Base-LX specifications, one very interesting anomaly was revealed associated with the use of laser transmitters in conjunction with multimode fiber.

The multimode fiber was designed to be used together with light emitting diodes (emission spectrum 30-50 ns). Incoherent radiation from such LEDs enters the fiber over the entire area of ​​the light-carrying core. As a result, a huge number of mode groups are excited in the fiber. The propagating signal lends itself well to description in the language of intermode dispersion. The efficiency of using such LEDs as transmitters in the Gigabit Ethernet standard is low due to the very high modulation frequency - the bit rate in the optical line is 1250 Mbaud, and the duration of one pulse is 0.8 ns. The maximum speed, when LEDs are still used for signal transmission over multimode fiber, is 622.08 Mbps (STM-4, taking into account the redundancy of the 8B / 10B code, the bit rate in the optical line is 777.6 Mbaud). Therefore, Gigabit Ethernet became the first standard to regulate the use of optical laser transmitters in conjunction with multimode fiber. The area of ​​input of radiation into the fiber from the laser is much smaller than the size of the core of a multimode fiber. This fact in itself does not yet lead to a problem. At the same time, in the technological process of manufacturing standard commercial multimode fibers, some defects (deviations within the allowable range) that are not critical for traditional use of the fiber are allowed, which are most concentrated near the axis of the fiber core. Although such a multimode fiber fully meets the requirements of the standard, coherent laser light introduced into the center of such a fiber, passing through regions of inhomogeneity of the refractive index, is able to split into a small number of modes, which then propagate along the fiber by different optical paths and at different speeds. This phenomenon is known as differential mode delay DMD. As a result, a phase shift appears between the modes, leading to unwanted interference on the receiving side and to a significant increase in the number of errors (Fig. 3a). Note that the effect manifests itself only under the simultaneous combination of a number of circumstances: a less successful fiber, a less successful laser transmitter (of course, meeting the standard) and less successful radiation input into the fiber. On the physical side, the DMD effect is associated with the fact that the energy from a coherent source is distributed within a small number of modes, while an incoherent source uniformly excites a huge number of modes. Research shows that the effect is stronger when using long wavelength lasers (transparency window 1300 nm).

Fig. 3. Propagation of coherent radiation in a multimode fiber: a) Manifestation of the effect of differential mode delay (DMD) at axial coupling of radiation; b) Off-axis coupling of coherent radiation into a multimode fiber.

This anomaly in the worst case can lead to a decrease in the maximum segment length based on the multimode FOC. Since the standard is supposed to provide a 100% performance guarantee, the maximum segment length should be regulated taking into account the possible manifestation of the DMD effect.

1000Base-LX interface... In order to maintain a greater distance and avoid the unpredictability of the behavior of the Gigabit Ethernet link due to anomaly, it is proposed to inject radiation into the off-center part of the multimode fiber core. Due to aperture divergence, radiation has time to be evenly distributed over the entire fiber core, greatly weakening the manifestation of the effect, although the maximum segment length remains limited after that (Table 2). MCP (mode conditioning patch-cords) single-mode transitional optical cords are specially designed, in which one of the connectors (namely, the one that is planned to be mated with multimode fiber) has a slight offset from the fiber core axis. An optical cord with one connector being a Duplex SC with an offset core and the other with a regular Duplex SC may be referred to as MCP Duplex SC - Duplex SC. Of course, such a cable is not suitable for use in traditional networks, for example, in Fast Ethernet, due to the high insertion loss at the interface with the MCP Duplex SC. The transient MCP can be a combined single-mode and multi-mode fiber and contain an inter-fiber bias element internally. Then, with a single-mode end, it is connected to a laser transmitter. As for the receiver, a standard multimode patch cord can be connected to it. The use of transitional MCP cords makes it possible to feed radiation into a multimode fiber through a region offset by 10-15 microns from the axis (Fig. 3b). Thus, it remains possible to use 1000Base-LX interface ports with single-mode FOCs, since there radiation will be injected strictly in the center of the fiber core.

1000Base-SX interface... Since the 1000Base-SX interface is standardized only for use with multimode fiber, the displacement of the radiation input area from the central axis of the fiber can be implemented inside the device itself, thereby eliminating the need to use an optical matching cord.

1000Base-T interface

1000Base-T is a standard Gigabit Ethernet interface for transmission over unshielded twisted pair Category 5 and higher over distances up to 100 meters. For transmission, all four pairs of copper cable are used, the transmission rate for one pair is 250 Mbit / s. It is assumed that the standard will provide full-duplex transmission, and data on each pair will be transmitted simultaneously in two directions at once - dual duplex. 1000Base-T. Technically, it turned out to be quite difficult to implement 1 Gbps duplex transmission over UTP cat.5 twisted pair, much more difficult than in the 100Base-TX standard. The influence of near and far crosstalk from three adjacent twisted pairs on a given pair in a four-pair cable requires the development of a special scrambled noise-immune transmission, and an intelligent signal recognition and restoration unit at reception. Several coding methods were initially considered as candidates for approval in the 1000Base-T standard, including: 5-level pulse-amplitude coding PAM-5; quadrature amplitude modulation QAM-25, etc. Below are brief ideas of PAM-5, finally approved as a standard.

Why 5-level coding. Common 4-level coding processes incoming bits in pairs. In total, there are 4 different combinations - 00, 01, 10, 11. The transmitter can set its own voltage level of the transmitted signal for each pair of bits, which halves the modulation frequency of the four-level signal, 125 MHz instead of 250 MHz, (Fig. 4), and therefore radiation frequency. A fifth level has been added to create code redundancy. As a result, it becomes possible to correct errors at the reception. This gives an additional 6 dB signal-to-noise ratio.

Fig. 4. PAM-4 4-level coding scheme

MAC level

The Gigabit Ethernet MAC layer uses the same CSMA / CD transfer protocol as its Ethernet and Fast Ethernet ancestors. The main restrictions on the maximum length of a segment (or collision domain) are determined by this protocol.

The Ethernet IEEE 802.3 standard has a minimum frame size of 64 bytes. It is the value of the minimum frame size that determines the maximum allowable distance between stations (diameter of the collision domain). The time that the station transmits such a frame - channel time - is 512 BT or 51.2 μs. The maximum length of the Ethernet network is determined from the collision resolution condition, namely, the time it takes for the signal to reach the remote node and return RDT back should not exceed 512 BT (excluding the preamble).

When switching from Ethernet to Fast Ethernet, the transmission speed increases, and the translation time of a 64-byte frame is correspondingly reduced - it is equal to 512 BT or 5.12 μs (in Fast Ethernet 1 BT = 0.01 μs). In order to be able to detect all collisions until the end of the frame transmission, as before, one of the conditions must be met:

Fast Ethernet kept the same minimum frame size as Ethernet. This retained compatibility, but resulted in a significant reduction in the collision domain diameter.

Again, by virtue of its continuity, the Gigabit Ethernet standard must support the same minimum and maximum frame sizes that are accepted in Ethernet and Fast Ethernet. But as the transmission speed increases, the transmission time for a packet of the same length decreases accordingly. While maintaining the same minimum frame length, this would lead to a decrease in the network diameter, which would not exceed 20 meters, which could be of little use. Therefore, when developing the Gigabit Ethernet standard, it was decided to increase the channel time. In Gigabit Ethernet, it is 4096 BT and is 8 times faster than Ethernet and Fast Ethernet. However, to maintain compatibility with the Ethernet and Fast Ethernet standards, the minimum frame size was not increased, but an additional field was added to the frame, called "media extension".

carrier extension

The symbols in the additional field usually do not carry service information, but they fill the channel and increase the "collision window". As a result, the collision will be recorded by all stations with a larger collision domain diameter.

If the station wishes to transmit a short (less than 512 bytes) frame, this field is added to the transmission - a carrier extension that complements the frame to 512 bytes. The checksum field is calculated only for the original frame and does not apply to the extension field. When a frame is received, the extension field is discarded. Therefore, the LLC layer does not even know about the presence of the extension field. If the frame size is equal to or greater than 512 bytes, then there is no media extension field. Figure 5 shows the Gigabit Ethernet frame format when using media expansion.

Fig. 5. Gigabit Ethernet frame with media extension field.

packet bursting

Media expansion is the most natural solution to maintain Fast Ethernet compatibility and the same collision domain diameter. But it wasted bandwidth. Up to 448 bytes (512-64) can be wasted when transmitting a short frame. During the development stage of the Gigabit Ethernet standard, NBase Communications made a proposal to upgrade the standard. This upgrade, called batch congestion, allows for more efficient use of the extension field. If the station / switch has several small frames to send, then the first frame is padded with a carrier expansion field to 512 bytes and sent. The rest of the frames are sent after a minimum interframe interval of 96 bits, with one important exception - the interframe gap is filled with extension symbols (Fig. 6a). Thus, the medium does not become silent between the sending of short original frames, and no other device on the network can interfere with the transmission. Such frame alignment can occur until the total number of transmitted bytes exceeds 1518. Packet congestion reduces the likelihood of collisions, since an overloaded frame can collide only at the stage of transmission of its first original frame, including media expansion, which certainly increases network performance. especially at heavy loads (Fig. 6-b).

Fig. 6. Packet congestion: a) frame transmission; b) bandwidth behavior.

According to the materials of the company "Telecom Transport"