Network Port Literacy One: Network card preliminary understanding

The network adapter is also known as the NIC or network interface card (NIC), the English name network Interface card. It is a device that enables computers to be networked. The NIC is the network adapter that connects the PC to the LAN. The NIC is plugged into the computer's motherboard slot, It is responsible for transferring the data that the user wants to pass to a format that can be recognized by other devices on the network. The data is transmitted in the computer bus in parallel, that is, the data is transmitted by side, while the physical cable in the network says that the data is transmitted in a serial bit-stream mode, The network adapter undertakes the conversion between the serial data and the parallel data. The network card before sending the data with the receiving network card to determine the maximum size of the data sent, the size of the amount of data sent, the interval between two sent data, waiting for the confirmation time, each network card can withstand the maximum amount of data before overflow, the speed of data transmission.

Its main technical parameters are bandwidth, bus mode, electrical interface mode and so on. Its basic functions are: from parallel to serial data conversion, package assembly and disassembly, network access control, data cache and network signal.

The main working principle of the network card: When sending data, the computer writes the data to be transmitted in parallel to the network card cache, the network card to transmit the data into the encoding (10M Ethernet using the Manchester special code, 100M ethernet using the differential Manchester code), serial sent to the transmission medium. When receiving data, the opposite is true.

1. Basic structure of NIC

Take the most common PCI interface network card as an example, a network card mainly by the PCB circuit board, the main chip, data mercury, gold finger (bus socket interface), Bootrom,eeprom, crystal oscillator, RJ45 interface, indicators, fixed tablets and so on, as well as some diodes, resistor capacitance and so on. The network card includes hardware and firmware programs (software routines in read-only memory) that implement the functions of logical link control and media access control, as well as a unique hardware address, MAC address, and a cache on the NIC. The network card must be assigned interrupt IRQ and basic I/O port address, The base memory address and transceiver (transceiver) must also be set

1. Network card control chip: The most important component of the network card, is the network card control center, like the computer's CPU, control the work of the entire network card, responsible for data transmission and connection when the signal detection. The early 10/100mbps dual speed network card will use two control chips (unit) It is used to control the operation of two different rate environments, while the more advanced products usually have only one chip to control the two speeds.

The common 10/100/1000m bps adaptive nic chip has Intel's 8254* series, Broadcom's bcm57** series, Marvell's
88e8001/88e8053/88e806* series, Realtek RTL8169S-32/64,RTL8110S-32/64 (LOM), RTL8169SB,RTL8110SB (LOM), RTL8168 (PCI Express), RTL8111 (Lom,pci Express) series, VIA's vt612* series and more.

3. Crystal oscillator: Responsible for generating the network card all chip operation clock, the principle of the same as the crystal oscillator on the motherboard, usually the network card is used 20 or 25hz crystal oscillator. Gigabit NICs use 62.5MHz or 125MHz oscillators.
5. Boot ROM slot: This slot in the NIC is vacant if no special requirement. Typically used with the boot ROM chip, the primary function is to boot the computer into the operating system via the server. Boot ROM is the boot chip, so that the computer can not have the hard disk, floppy drive and optical drive, Boot directly from the server to become a non-hard disk without floppy drive workstation. The data can not be output without the floppy drive, which also provides the ability to keep the data confidential. At the same time, you can save the cost of purchasing these computer parts. Be aware of what network operating system you use when using the boot ROM, usually with boot ROM for nt,boot rom for unix,boot ROM for NetWare etc., boot ROM boot chip to be purchased by itself.
7. EEPROM: The former old network card is set by the jumper or dip switch to set the IRQ,DMA and I/O port equivalent, and now the network card is used software settings, almost invisible jumper. The status of various network cards and network card information and other data are present in this small EEPROM, It is automatically set. It records the supplier ID of the NIC chip, the subsystem vendor ID, the MAC address of the network card, some configuration of the NIC, such as the address of the PHY on the SMI bus, the capacity of the bootrom, whether the Bootrom boot system is enabled, and so on.
9. Data Mercury: This is a device that is available on a consumer-grade PCI network card, which is also known as a network transformer or a network-isolated transformer. It acts on a network card with two main functions, one is the transmission of data, it sends the PHY out of the differential signal by differential mode coupled coil coupled filter to enhance the signal, And by the conversion of the electromagnetic field coupled to the different levels of the other end of the connection network cable, the first is to isolate the different levels of the cable connection between different networks, in order to prevent different voltages through the network cable transmission damage device. In addition, data mercury can also play a certain role in lightning protection of equipment.
11. Rj-45 and BNC connector: RJ-45 is a network interface with twisted pair as transmission medium, which is used most frequently in 100mbps network. The BNC uses a thin coaxial cable as the transmission medium.
13. Signal light: After the network card there will be two to three different lights, the role is to display the current network connection status, usually with TX and RX two information. TX Representative is sending data, RX Representative is receiving data, if you see two lights at the same time, it represents the current full-duplex operation state, It is also possible to identify whether a full-duplex network card is in a full-duplex networked environment. There are also some low-speed network card only with one light to represent the signal, through a different light transformation to indicate whether the network conduction.
15. WOL: Some network cards will have WOL function, WOL network power on the function (wake on line). It can be sent by another computer, using software to make a special format of the packet to a computer equipped with a WOL function card, and the network card receives these special format packets, Will command the computer to turn on the power, there are more and more network cards to support the function of the Internet boot.

2. Classification of NIC

• The transfer rate can be divided into:

10Mbps network card, 100Mbps network card, 1000Mbps network card, 10GMbps network card. At present, there are three kinds of architectures, 10baset,100basetx and Base2, the first two are the rj-45 twisted pair as the transmission medium, The transfer rates are 10Mbps and 100Mbps, respectively. And the twisted pair is divided into category 1 to category 55 kinds of specifications, respectively, have different use and bandwidth, category is usually referred to as cat, as long as the use of CAT5 specification twisted pair can be used for 10/ 100mbps network card. The 10BASE2 architecture uses a thin coaxial cable as the transmission medium with a transfer rate of only 10Mbps. The 10Mbps or 100Mbps mentioned here refers to the maximum transfer rate on the NIC, not the actual transfer speed on the network. The actual speed to take into account the distance transmitted, the quality of the line, and whether the network congestion and other factors, the bps referred to here refers to the bit per second (1 byte=8 bit). And 100Mbps is called high-speed Ethernet card (Fast Ethernet), mostly pci/ Pci-e interface. Currently on the market, the PCI network has the function of 10/100/1000mbps automatic switch, will automatically adjust the network speed according to the network connection environment. The Gigabit Ethernet port is used for high-speed links or backbone between the switch or switch and the server.

• The interface types can be divided into:

ISA interface card, pci/pci-x/PCI-E interface card, USB interface card and laptop-specific PCMCIA interface. Now the NIC of the ISA interface adopts the 16bit bus width, which is characterized by the use of programmed I/O mode to transmit data, The data must be transmitted through the CPU on the I/O in a small window, as a communication between the network card and PC pipeline, need to occupy a high CPU utilization, in the transfer of large amounts of data inefficient. PCI Interface network card is a 32bit bus bandwidth, using bus master data transfer mode, transmission data is controlled by the control chip on the network card, do not have to through the I/O port and CPU, can greatly reduce the CPU occupancy rate, the current product is more than 10/ 100Mbps Two-speed automatic detection switch card.

• The transfer method can be divided into:

Half-duplex network card, full-duplex network card. Half-Duplex network adapter cannot complete the operation of receiving and transmitting data at the same time, such as the network architecture of 10BASE2 using a thin coaxial cable is half-duplex, and can only transmit or receive data during the same time. Low efficiency. To use a full-duplex network, you must use a twisted pair as a transmission line to achieve, and also use a full-duplex hub, to use a 10base or 100BASETX network architecture, of course, the NIC is also full-duplex products.

• The transmission medium can be divided into:

RJ-45 twisted pair of network card and BNC coaxial cable two, some network card has two kinds of connectors, can be applied to two network lines, but not two connectors at the same time. There is also a NIC for the fiber interface, usually with a bandwidth of up to three Mbps.

• Other Network cards:

The physical media transmitted from the network also has a wireless card that transmits data using 2.4GHz of radio waves. There are currently two specifications for IEEE 802.11 and 802.11B, the highest transmission rates are 2Mbps and 11Mbps, the interface has PCI,USB and PCMCIA several.

Reprint Address: http://www.cnblogs.com/jason-lu/p/3198424.html

Network Port Literacy One: Network card preliminary understanding