Appearance of the classic adapter
Physically, the adapter is a board with microcircuits and connectors. Despite the fact that many modern models of these devices are integrated into the motherboard and, in fact, are a set of microcircuits and a connector brought out to a convenient place, they still continue to be called cards. There are also names such as network adapter and network card. The device is able to convert an electrical signal coming from a connected cable into data that a computer can understand.
How network cards work
The adapter is located at the second, link layer of the OSI model. For the operating system to know how to interact with the network card, a driver must be installed. Usually they are supplied with the device or are available on the manufacturer's official website. Many versions of Windows are able to pick up adapters installed in the system without installing additional drivers. As for Linux distributions, almost all of them are capable of working with an adapter out of the box.
What is a network card in a computer for, and how does it work? When receiving data, the card receives a set of signals, as a result of the conversion of which it receives a certain sequence of bits. Then the checksum of this piece of data is checked. If it matches, then they are placed in RAM. If not, they are discarded and an error is signaled. When transferring data to a cable, all steps are performed in reverse order. It should be noted that manufacturers of network adapters, in order to make them less expensive, shift many tasks onto the shoulders of drivers. In server solutions, network cards can have their own processor, which itself is responsible for processing, encrypting and converting signals.
A little educational program: OSI is a generally accepted model and an international standard by which protocols and devices are developed. It has 7 levels, each of which implements its own task. A short list of them looks like this: physical (cables, radio channels), channel (network cards, DSL), network (routers), transport (TCP, UDP), session (exchange and maintenance of information flows), presentation (data transformation), applied (protocols HTTP, FTP, bitTorrent).
Basic characteristics of network cards
The adapters have a lot of characteristics. But for home use, most of them are useless. Therefore, we will consider those moments that, in one way or another, significantly affect the price and scope of use:
- baud rate... Almost all modern devices, even those for 500 rubles, can support a transmission speed of 1 Gigabit. Therefore, there is no significant difference here. However, it is worth paying attention to this parameter;
- interface or connection type. This is how the network card will connect to your computer. Now the market is dominated by three types of connection: USB, PCI and PCI-E;
- number of RJ-45 connectors... If you plan to use a computer to transmit the Internet over the next link in the network, or you just need a local network, then you should take a closer look at the models that have 2 or more connectors on board;
- card profile. There is a misconception that a low profile card, or Low Profile, means that it only takes up one slot. This is not true. Low profile in network as well as video cards means board width. In simple terms, this is the height of the card above the motherboard. Although almost all network cards are low-profile, if there is not enough space inside the system unit, you need to stop at a device marked with Low Profile.
All other characteristics are not so important, and in most cases they can be neglected.
Types of network cards by connection method
Earlier we touched upon the topic of connecting adapters a little. Let's analyze it in more detail. All such devices can be divided into three large types: integrated, internal and external.
Integrated or embedded
Probably the most common type. They are chips mounted on the motherboard. Accordingly, all the necessary connectors are displayed on the rear panel. Most modern motherboards come with this type of network adapter. It is worth noting that Wi-Fi modules are also network cards for a computer, however, they are usually called that - "Wi-Fi module", of course, if it is not integrated.
Internal PCI and PCI-E NICs
These devices are separate boards that are mounted in specific connectors or buses. The most common ones are PCI and PCI-E. The first form factor is gradually becoming obsolete and giving way to PCI-E. Nevertheless, such cards can still be found on the market. PCI-E can be of various lengths. But when specifying characteristics, this parameter is usually discarded, since it is standardized.
PCI and PCI-E are easy to distinguish
It is worth mentioning the PCMCIA standard separately. This specification was developed as an add-on module and was very widely used in laptops of the past. With its help, it was possible to connect not only network cards, but also many types of other equipment. Today this standard is practically not supported.
External USB Network Cards
A relatively new trend in the adapter market. It is an external device connected to the USB port. Outwardly it looks like a USB flash drive. All microcircuits are hidden in a neat case. In the simplest case, it can have one RJ-45 connector. A very convenient and compact form of a network card.
What it looks like and where is the network card in the computer
Finding the built-in network card in your computer is not that difficult. The card that has an RJ-45 connector, a standard connector for almost all Internet providers, will be a network board. In addition, many devices are equipped with LED indicators for operation.
How to find out the network card of the computer, if it is integrated? It also has an RJ-45 connector on the back of the system unit, however, the chip itself can be soldered anywhere on the motherboard. To find it, you have to refer to the schematic map that usually comes with the motherboard.
What is a network card in a laptop? In most cases, this is a separate Wi-Fi chip and a separate Ethernet. If the first one stands out noticeably, then the second one can be a very tiny chip somewhere in the backyard of the motherboard.
How to set up a computer's network card
You need to configure the adapter based on your needs. So, in most cases, after installing and connecting the cable, it should work out of the box. Quite often, you have to change the settings for obtaining an IP address. There are two types: obtaining an address automatically and specifying manually. In most cases, the automatic option is sufficient. You can check which mode is set or change it by going to the Start Menu Control Panel.
Here you need to find the "Network and Sharing Center" and click on the link "Local Area Connection".
Current connection status window
A status window will appear, in which we are interested in the "Properties" button. In the new window that opens, select the "Internet Protocol version 4" item and click on the "Properties" button again.
Protocols require TCP / IP version 4 or 6
The next window will offer to choose the option of obtaining an IP address by setting the switch to the desired mode.
In most cases, the IP address is given automatically, so you hardly need to configure it
In a special publication, we will tell you about Wi-Fi routers. You will find out which Wi-Fi router is better, their technical characteristics, how to connect it yourself and check the prices.
What to do if the computer does not see the network card
Quite a common problem. It can be solved in different ways, depending on the situation. Let's consider solutions for integrated and internal cards. The situation when the computer does not see the card can arise for several reasons:
- the device is disabled in the BIOS;
- drivers are not installed;
- physical malfunction.
In all other situations, the card should appear in the device manager at least as an unidentified device, which will allow installing the drivers. The Onboard H / W LAN item is responsible for disabling the network card in the BIOS. It must be in Enabled mode. It is interesting that here, in the BIOS, the disconnection of the Green LAN item sometimes helps to detect the card. This is not a universal approach, since these items may be completely absent in different models of motherboards.
BIOS standard for most motherboard cards
As such, the absence of drivers will usually still detect the network adapter in Device Manager. If the card is built-in, then you will need to install the motherboard drivers for detection. If in laptops it is very easy to do this, having found the required driver package by the device model, then for stationary systems you will have to accurately determine the motherboard model and download the drivers from the official website.
ATTENTION!
Always download drivers only from the official developer sites. This will prevent viruses and malware from entering your system and use the most recent software version.
As for the physical malfunction, there is nothing you can do about it. Especially if the card is built-in. All that remains is to buy a new external or internal one.
How to choose a network card for your computer
Basically, the choice of cards for a computer comes from the range of PCI-models. You can, of course, look in the direction of USB, but why occupy an external connector in the hospital, if you can carefully install the board inside? PCI can be different too. Specifically, PCI is an earlier format for connecting various devices. PCI-E is more widespread now. Its main difference is its higher throughput. Therefore, before buying, it is advisable to find out which connectors are available on the motherboard, and based on this, choose a network device. By the way, most network cards have a PCI-E x1 slot, that is, with one lane.
In the network equipment market, brand is equally important. Now, probably, only the lazy does not release network adapters. Among the assortment you can find both well-known brands and semi-basement Chinese no-names. Naturally, the quality and reliability of work will be higher for solid and expensive cards. But you can find a middle ground by choosing an inexpensive, possibly Chinese, but factory copy. We will review popular manufacturing companies a little later.
In terms of speed, the average user is unlikely to feel the difference between Gigabit and 100 Mbps. Unless he plans to transfer large files in large quantities on the local network. With the existing technologies of Internet providers, buying a network adapter with a speed higher than 100 megabits is hardly the best solution. Network cards for a computer with Wi-Fi are more sensitive to parameters such as speed, the ability to work in multiple frequencies, and the protocols supported.
How to choose a network card for a laptop
The era of PCMCIA cards is over. It is very difficult to find such devices on the market now. Therefore, the solution for laptops is network cards with a USB connector. The only noticeable difference between the two is the USB version of the interface. Here, the higher the better. But do not forget that the port on the laptop must be the same version for full compatibility and the full potential of the device.
How to install a network card on a computer
Installing a USB adapter into your computer is very simple - plug it in and you're done. Therefore, we will consider the option of mounting the internal adapter. Before connecting the network card to the computer, you need to remove the cap on the back of the system unit opposite the corresponding PCI or PCI-E slot. Then you just need to carefully insert the device into the slot and tighten the mounting plate with the screw. Everything. Naturally, the entire operation must be carried out with the computer turned off.
Popular card makers and their products
At the mention of network cards, several manufacturers come to mind at once, the names of which are always on hearing: Intel, Tp-Link, D-Link, HP, gembird and others. Since network cards do not have special extended functionality, let's briefly go through the manufacturers and look at their devices.
Intel EXPI9301CT
Intel knows how to produce not only processors, but also network adapters and many other devices
Gigabit low profile network adapter from a reputable company. Has 1 RJ-45 connector, works with all known operating systems. Connection type - PCI-E. You can buy such a network card for a computer for 2,000 rubles.
Here's what users say about it.
Review of Intel EXPI9301CT
More details on Yandex Market: https://market.yandex.ru/product/4762772/reviews?track=tabs
TP-Link TG-3468
Budget option from TP-Link
A gigabit option from the budget segment costing 500 rubles. Connection bus - PCI-E. There is 1 RJ-45 connector. Additional features include Wake-on-Lan support.
Review of TP-Link TG-3468
More details on Yandex Market: https://market.yandex.ru/product/3530612/reviews?track=tabs
D-Link DUB-E100
Compact and handy device
Simple USB adapter. The maximum data transfer rate is 100 Mbps. The USB version is 2.0. Supported by all known operating systems. One connector. The adapter costs 800 rubles.
Review of D-Link DUB-E100
More details on Yandex Market: https://market.yandex.ru/product/811694/reviews?track=tabs
3COM 3C905C-TX-M
Classics of network adapters
A regular 100 Mbps adapter with a PCI bus. 1 RJ-45 connector. Not all operating systems are supported. The cost of the device is 3,000 rubles.
Reviews of 3COM 3C905C-TX-M
More details on Yandex Market: https://market.yandex.ru/product/804511/reviews?track=tabs
ASUS NX1101
Low profile will help save space for other indoor modules
Card from Asus at 1000 Mbps. The PCI bus is used for connection. RJ-45 connector - 1. The device costs 930 rubles.
Review of ASUS NX1101
More details on Yandex Market: https://market.yandex.ru/product/968961/reviews?track=tabs
Apple MD463ZM / A
Apple has its own connection standards
A device focused on Apple products. Accordingly, instead of a USB port, it uses its own Thunderbolt interface. The data transfer rate is declared up to 1 Gigabit. The connector is 1 type RJ-45. The adapter costs 2,100 rubles.
Review of Apple MD463ZM / A
More details on Yandex Market: https://market.yandex.ru/product/8356351/reviews?track=tabs
Acorp L-1000S
Simple externally and internally model
At one time, Acorp was one of the leaders in the production of network equipment, in particular, Dial-up modems. This card is a PCI 2.3 network adapter. The data transfer rate is 1 Gigabit. 1 RJ-45 port is used to connect the cable. There is a Wake-on-LAN option. The adapter costs only 370 rubles.
Review of Acorp L-1000S
More details on Yandex Market: https://market.yandex.ru/product/974078/reviews?track=tabs
ST Lab U-790
You can put this model in your pocket and take it with you on the road
Simple 1000 Mbps network adapter. Connected via USB 3.0. There is 1 RJ-45 connector for the cable. All modern systems are supported. You can buy a card for 1,500 rubles.
ST Lab U-790
More details on Yandex Market: https://market.yandex.ru/product/9332263/reviews?track=tabs
Zyxel GN680-T
Zyxel, or in common people "Zuhel", is reliable and easy to operate
Gigabit PCI Card 2.3. One RJ-45 connector and Wake-on-LAN. A large list of operating systems is supported. The cost is 1,300 rubles.
Review of Zyxel GN680-T
More details on Yandex Market: https://market.yandex.ru/product/2066600/reviews?track=tabs
5Bites UA2-45-02
The model can be presented in two colors: black and white
Quite a simple and budget device. Its cost is only 400 rubles. For that kind of money, the user will receive 100 Mbit / s, a USB 2.0 interface and 1 RJ-45 port. Almost all systems are supported.
Review of 5Bites UA2-45-02
In the world of technological progress and global computerization, rapidly developing technologies have touched every modern user. Access to the World Wide Web is no longer limited to the use of only one computer.
Today, in every home, almost all family members, young and old, have one or more different devices with access to the network. In this case, it is very convenient to install a Wi-Fi access point and distribute a signal to any connected equipment. Modern devices such as laptops, tablets, phones have built-in Wi-Fi receivers, making them easy to connect to a network.
A network card, or network adapter, is the part of a computer that makes it interact with the network. With the exception of outdated device models, many laptops and computers are equipped with a network adapter during production. This provides the ability to connect to the internet without purchasing a separate item. But, despite the built-in adapter, you can and should purchase an additional external device, expanding the data exchange capabilities.
The network card can be integrated into the motherboard or external. Regardless of the variety, it is assigned a Mac address, through which the identification of the computer connected to the network is carried out.
Wi-Fi network card
The computer can be connected to the Internet physically using a cable connected to the network port of the PC, or wirelessly, which does not require the use of connectors.
The Wi-Fi network card causes the computer to receive a signal from the wireless network. It can be connected to the PCI slot of the motherboard or the USB port of a computer, less often to Ethernet (basically this type of connection is applicable to old devices). A Wi-Fi card plugged into the USB port of a PC or laptop is the most convenient in terms of mobility, it is easy to connect it to another device if necessary.
In addition to the connection method and appearance, there are differences in the speed and power of the adapter. Some cards are only capable of receiving signals, while others are also capable of transmitting. Adapters equipped with Soft AP function provide Wi-Fi access point creation.
The range of signal reception and transmission can be carried out both over long distances up to hundreds of meters, and limited to a small access area. As in the case of a router, there is no need to use too powerful network cards for home use, unless, of course, you are going to distribute Wi-Fi to all neighbors or pick up someone else's signal. In addition, the price will depend on the power of the model, and it is inappropriate to overpay for a card that will work in a small area. More hefty models of adapters are applicable on a large territory of offices or enterprises.
How a Wi-Fi adapter works
Access to the Internet over a wireless network is carried out thanks to the joint work of a network card and a router or modem. Wi-Fi technology works on a specific frequency range. Data exchange with the network is carried out through a router or modem, which communicates with the air by radio waves. For the computer to perceive the radio signal, a network card is used, which reads and converts the signal into an electronic one. All devices equipped with an adapter and within range of the router's transmitter will receive the received signal. To digitize the data for their recognition by the device, the adapter is equipped with a microcircuit and special software that controls the operation of the module. For the correct operation process, the necessary drivers must be installed.
Types of adapters
All adapters fall into two main categories:
External. Such network devices are connected via the USB port of a computer or laptop. They do not have a high data transfer rate, but they pleasantly compensate for this disadvantage with a price, which is why they are the most popular today. In appearance, such adapters are similar to USB drives. To get started, you need to plug the device into a free port and connect to a wireless connection.
Internal, or built-in. They are connected to the PCI connector of the motherboard. To install this type of adapter, you will have to remove the cover of the system unit. The size of the built-in network card is larger than that of the external one. This variant of the device has good bandwidth, resulting in a high data transfer rate. The price of the issue will be significantly higher than that of external adapters.
There is another, not widely used version of devices - card (Card-Bus). Adapters of this type are connected to a PC Card slot, if one is available in your computer equipment.
Wireless network cards can be connected not only to computers and laptops. A separate niche is occupied by external adapters for TVs. They can be both universal and designed for specific models. If the TV is not equipped with a Wi-Fi receiver, but has an appropriate connector, you can purchase an adapter compatible with it to connect to a network source.
Antennas for network cards
A device with an external antenna receives the signal better. Of course, the dimensions of the receiver do not always contribute to comfort, so you can choose an adapter with a removable antenna or with a connector, where you can insert it if necessary.
The antenna power when choosing a device should be appropriate for the location where you want to install the network.
The number of antennas affects the data transfer rate. Models equipped with removable antennas are very convenient in the case of a distant location of the router; if necessary, it is possible to install a more powerful structure for receiving radio waves. External antennas provide long range.
Installing and configuring a Wi-Fi adapter
Despite the significant differences in network cards by type and type of connection, they are all configured according to a similar principle.
First, you need to connect the adapter physically to the desired connector on your computer or laptop. Windows will detect new hardware. Although there will always be compatible programs in the system set of programs, for correct operation it is better to install the drivers from the disk that is attached to the network device. You can also download the necessary software from the manufacturer's official website. The exchange of data through the adapter is due to the driver, which is why it is better to install software that is suitable specifically for your device model.
After installing the Wi-Fi card, the network connection icon will appear, click on it and find the TCP / IP Internet protocol in the properties of the wireless network connection. Here you need to enter the settings of the network parameters, they need to be found out by contacting the technical support of your provider, and entered in the fields for filling. Settings can also be assigned automatically. When you have selected the desired options and access points, all that remains is to assign a Mac address to the card. This task is performed by the network administrator, to do this, call technical support and notify about the adapter change and the need to change the Mac address.
When choosing a network device, pay attention not only to the functionality, because you will not use all the capabilities of the card, and the price for a wide range of functions will increase several times. Pay attention to some factors, such as the size of your room in which the Wi-Fi network will be used, the distance between the router and the computer, and the thickness of the walls. The manufacturer also plays a significant role in the reliability of products, it is better to choose a proven, proven product quality, such as in the computer equipment market in abundance. It is advisable to purchase adapters from the same manufacturer as the router or modem, thereby ensuring the best device compatibility.
A network card is a component of a computer that is used to connect to a local network. These devices rarely cause any problems, therefore, in most cases, users do not even know which network card is on their computer.
However, such information may be needed, for example, to find suitable drivers. In this material, we will look at 3 ways at once, how you can find out the name of the network card used on the computer.
Method number 1. Device Manager.
If you want to find out which network card is on your computer, then the easiest way is to use the "Device Manager". You can open Device Manager in different ways. The easiest option is to press the Windows-R key combination and enter the command "mmc devmgmt.msc" in the window that appears.
You can also use the search in the Start menu. To do this, open the "Start" menu and enter "Device Manager" in the search box. After that, the system will find the required program and offer to open it.
After opening "Device Manager", expand the "Network adapters" list. In this list, you will see the name of the network card that is installed on your computer.
It should be noted that sometimes the list of "Network adapters" may contain virtual network cards. Such cards may appear after installing some programs (for example, VirtualBox).
Method number 2. Command line.
You can also find out which network card is on your computer using the "Windows Command Prompt". To do this, you first need to run the command line. This can be done in different ways. For example, you can press the Windows-R key combination and execute the "cmd" command in the window that appears.
After opening the command line, you need to run the command "ipconfig / all" in it.
As a result, the screen will display information about all network connections used on your computer.
Here, among other information, for each network connection, the name of the network card will be indicated. It will be indicated in the "Description" line.
Method number 3. Programs.
You can also find out the name of the network card that is on the computer using special programs to view the characteristics of the computer. For example, you can use a free program. Install this program on your computer and run it.
After starting the program, open the "Network" section. All possible information about your network connections and network cards will be here.
Any modern computing system is a complex of interacting devices, each of which performs some specific functions. For example, a video card is designed to generate signals that are converted by the monitor into an image; sound - for audio output; network card - for connecting several computer systems, etc.
All of them, being collected into a single system, form a computer. That is why it is so important to understand the features of the devices, to know their main characteristics. The topic of today's article is the network card.
Currently, the market offers several modifications of such devices, which differ from each other by the manufacturer, the used communication chip, the maximum operating speed, the method of connection to the computer motherboard and the data transmission medium. Let's consider each moment in more detail.
Manufacturer
There are several companies that manufacture such devices. When choosing, you should pay special attention to the chip used - it is its characteristics that determine the capabilities that are realized. These can be products from Realtek, Intel, Qualcomm, i.e. all those who are directly involved in production
Despite the fact that the main task of the devices is the same, the "firewood" for the network card (the program in the operating system that controls the work) from different manufacturers may have different additional capabilities. For example, intelligent power management, how the wake-up command is handled, and frame sizing are not present in all solutions, and the implementation may differ. If the network card must support specific capabilities, then the choice must be approached only thoroughly prepared. For ordinary users, any network card is suitable, the main thing is that the speed matches and the transmission principle is suitable.
In addition, the cost of functionally identical solutions largely depends on the manufacturer. When buying products from a renowned developer, you often have to overpay "for the name". It is believed that these models have higher reliability than budget models. This is partly true. At the same time, a D-Link network card (as well as from any other manufacturer) can be purchased for a different amount. The reasons for this will be indicated below.
Hardware capabilities
In order to process the digital data stream in a certain way, the network card performs a fairly large amount of calculations - it generates packets in accordance with standards, controls reception / transmission, etc.
And for this, the resources of the central processor core are used. That is why, with a large amount of transmitted data, a general slowdown can be observed. To solve this feature, the chips in some models of network cards are able to independently process the data stream without using it. This is called hardware processing. It can be complete or partial. Thus, for organizing a simple network, an inexpensive program-controlled card is suitable, but for more complex nodes it is recommended to pay attention to more advanced models.
Speed
Performance is one of the key characteristics of these devices. According to the standard, cards can support 10, 100, and 1000 megabits per second. All modern solutions in which an RJ-45 connector is used to connect a cable are compatible with each other, that is, the same cable can be used to connect models with 10 and 1000 Mbps. In this case, the protocols will be automatically reconfigured to a lower speed. Thus, if it is necessary to connect two computers in a 1 Gbit network, then, having the necessary cable and cards, this can be easily done. However, if there is an intermediate element between them, for example, a 100 Mbps switch, then the overall speed will be limited to it.
Wednesday
For cable can be used as well as radio frequency. Cards using the latter solution most often work over the Wi-Fi standard. They are very popular nowadays as networking is much easier. The transmission speed when using the radio channel does not exceed 300 Megabits.
Network board Also known as a network card, network adapter, Ethernet adapter, NIC (English network interface card) is a peripheral device that allows a computer to communicate with other devices on a network. Nowadays, especially in personal computers, network cards are quite often integrated into motherboards for convenience and reduce the cost of the entire computer as a whole.
Types
By constructive implementation, network cards are divided into:
- internal - separate cards inserted into the ISA, PCI or PCI-E slot;
- external, connected via USB or PCMCIA interface, mainly used in laptops;
- * built into the motherboard.
On 10-megabit network cards, 3 types of connectors are used to connect to a local network:
- 8P8C for twisted pair;
- BNC connector for thin coaxial cable;
- 15-pin transceiver AUI connector for thick coaxial cable.
- optical connector (en: 10BASE-FL and other 10 Mbit Ethernet standards)
On 100-megabit cards, either a twisted pair connector (8P8C, mistakenly called RJ-45, or an optical connector (SC, ST, MIC)) is installed.
One or more information LEDs are installed next to the twisted pair connector, indicating the presence of a connection and information transfer.
One of the first mainstream network cards was the NE1000 / NE2000 series from Novell with a BNC connector.
Network adapter parameters
When configuring the network adapter card, the following options may be available:
- IRQ hardware interrupt request line number
- DMA channel number (if supported)
- base I / O address
- RAM memory base address (if used)
- support for auto-negotiation duplex / half-duplex standards, speed
- support for tagged VLAN packets (802.1q) with the ability to filter packets of a given VLAN ID
- WOL (Wake-on-LAN) options
- Auto-MDI / MDI-X function automatic selection of the mode of operation for straight or cross-crimped twisted pair
Depending on the power and complexity of the network card, it can implement computational functions (mainly counting and generating checksums of frames) in hardware or software (by a driver of a network card using a central processor).
Server network cards can be supplied with two (or more) network connectors. Some network cards (built into the motherboard) also provide firewall functionality (like nforce).
Functions and characteristics of network adapters
A network adapter (Network Interface Card (or Controller), NIC), together with its driver, implements the second, link layer of the open systems model at the end node of the network - the computer. More precisely, in a network operating system, a pair of adapter and driver performs only the functions of the physical and MAC layers, while the LLC layer is usually implemented by the operating system module, which is the same for all drivers and network adapters. Actually, this is how it should be in accordance with the model of the IEEE 802 protocol stack. For example, in Windows NT, the LLC level is implemented in the NDIS module, which is common to all network adapter drivers, regardless of which technology the driver supports.
The network adapter together with the driver perform two operations: frame transmission and reception. The transfer of a frame from a computer to a cable consists of the following steps (some may be missing, depending on the accepted encoding methods):
- Formatting the MAC layer data frame in which the LLC frame is encapsulated (with flags 01111110 discarded). Filling in the destination and source addresses, calculating the checksum. Receiving the LLC data frame via the interlayer interface along with the address information of the MAC layer. Typically, communication between protocols inside a computer occurs through buffers located in RAM. Data for transmission to the network is placed in these buffers by upper-layer protocols, which retrieve it from disk memory or from the file cache using the I / O subsystem of the operating system.
- Formation of code symbols when using redundant codes of type 4B / 5B. Scramble codes to obtain a more uniform signal spectrum. This step is not used in all protocols - for example, 10 Mbps Ethernet technology does without it.
- Outputting signals to the cable in accordance with the accepted line code - Manchester, NRZ1. MLT-3, etc.
- Isolation of signals against the background of noise. This operation can be performed by various specialized microcircuits or signal processors DSP. As a result, a certain bit sequence is formed in the adapter receiver, which, with a high degree of probability, coincides with the one sent by the transmitter.
- If the data was scrambled before being sent to the cable, then it is passed through the descrambler, after which the code symbols sent by the transmitter are restored in the adapter.
- Checking the checksum of the frame. If it is incorrect, then the frame is discarded, and the corresponding error code is transmitted to the LLC protocol through the interlayer interface upward. If the checksum is correct, then the LLC frame is extracted from the MAC frame and transmitted through the interlayer interface upward, to the LLC protocol. The LLC frame is placed in the RAM buffer.
The distribution of responsibilities between the network adapter and its driver is not defined by standards, so each manufacturer decides this issue independently. Typically, network adapters are classified as adapters for client computers and adapters for servers.
In adapters for client computers, much of the work is shifted to the driver, making the adapter simpler and cheaper. The disadvantage of this approach is the high degree of loading of the computer's central processor by routine work on transferring frames from the computer's RAM to the network. The central processor is forced to do this work instead of performing the user's application tasks.
Therefore, adapters designed for servers are usually equipped with their own processors, which independently perform most of the work of transferring frames from RAM to the network and vice versa. An example of such an adapter is the SMC EtherPower NIC with an embedded Intel i960 processor.
Depending on which protocol the adapter implements, adapters are divided into Ethernet adapters, Token Ring adapters, FDDI adapters, etc. hub, many Ethernet adapters today support two speeds and have a 10/100 prefix in their name. Some manufacturers call this property autosensitivity.
The network adapter must be configured before being installed in a computer. Configuring an adapter typically specifies the IRQ used by the adapter, the DMA channel (if the adapter supports DMA mode), and the base address of the I / O ports.
If the network adapter, computer hardware, and operating system support Plug-and-Play, the adapter and its driver are automatically configured. Otherwise, you must first configure the network adapter and then repeat its configuration parameters for the driver. In general, the details of the procedure for configuring a network adapter and its driver largely depend on the manufacturer of the adapter, as well as on the capabilities of the bus for which the adapter is designed.
Classification of network adapters
As an example of the classification of adapters, we use the approach of 3Com. 3Com believes that Ethernet network adapters have gone through three generations.
First generation
Adapters first generation were executed on discrete logic microcircuits, as a result of which they had low reliability. They had a buffer memory for only one frame, which led to poor adapter performance, since all frames were transferred from computer to network or from network to computer sequentially. In addition, the configuration of the first generation adapter was done manually using jumpers. A different driver was used for each type of adapter, and the interface between the driver and the network operating system was not standardized.
Second generation
In network adapters second generation to improve performance, they began to use the multi-frame buffering method. In this case, the next frame is loaded from the computer memory into the adapter buffer simultaneously with the transmission of the previous frame to the network. In the receive mode, after the adapter has completely received one frame, it can start transmitting this frame from the buffer to the computer memory at the same time it receives another frame from the network.
Second-generation network adapters widely use highly integrated microcircuits, which increases the reliability of the adapters. In addition, the drivers for these adapters are based on standard specifications. Second-generation adapters typically come with drivers that work in both the NDIS (Network Driver Interface Specification), developed by 3Com and Microsoft and approved by IBM, and the ODI (Open Driver Interface), developed by Novell.
Third generation
In network adapters third generation(among them 3Com refers its adapters of the EtherLink III family) a pipelined frame processing scheme is carried out. It lies in the fact that the processes of receiving a frame from the computer's RAM and transmitting it to the network are combined in time. Thus, after receiving the first few bytes of the frame, their transmission begins. This significantly (by 25-55%) increases the performance of the "RAM - adapter - physical channel - adapter - RAM" chain. This scheme is very sensitive to the transmission start threshold, that is, to the number of frame bytes that are loaded into the adapter buffer before starting transmission to the network. The third generation network adapter performs self-tuning of this parameter by analyzing the working environment, as well as by calculation, without the participation of the network administrator. Self-tuning provides the best possible performance for a particular combination of performance on the computer's internal bus, interrupt, and direct memory access.Third-generation adapters are based on Application-Specific Integrated Circuits (ASICs), which increase adapter performance and reliability while reducing cost. 3Com has named its pipelined frame processing technology Parallel Tasking, and other companies have implemented similar designs in their adapters as well. Improving adapter-to-memory link performance is critical to improving overall network performance, since the performance of a complex frame path, such as hubs, switches, routers, WANs, etc., is always determined by the performance of the slowest element of this route. Therefore, if the network adapter of the server or client computer is slow, no fast switches will be able to improve the speed of the network.
Today's network adapters can be classified as fourth generation... These adapters necessarily include an ASIC that performs the functions of the MAC-level (English MAC-PHY), the speed is developed up to 1 Gbit / s, as well as a large number of high-level functions. The set of such functions may include support for the RMON remote monitoring agent, frame prioritization scheme, functions for remote computer control, etc. Server versions of adapters almost necessarily have a powerful processor that offloads the central processor. An example of a Gen 4 network adapter is the 3Com Fast EtherLink XL 10/100 adapter.
