Network Port Literacy One: Network card preliminary understanding

Network Port Literacy One: Network card preliminary understanding

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

The main technical parameters of the network card 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), The serial is sent to the transmission medium. When receiving data, the opposite is true.

1. Basic structure of NIC

Take the most common PCI interface NIC as an example, a network card mainly by the PCB board, the main chip, data Mercury (? ), Gold finger (bus socket interface), Bootrom,eeprom, crystal oscillator, RJ45 interface, LED, fixed chip and so on, as well as some diodes, resistor capacitance and other components. The NIC includes hardware and firmware programs (software routines in read-only memory) The firmware program implements the functions of logical link control and media access control , and also records the unique hardware address i.e. MAC address , which is usually cached on the network card. The network card must be assigned interrupt IRQ and basic I/O port address, and must also set the base memory address Address) and transceivers (transceiver)

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.

Common 10/100/1000m bps Adaptive nic chip with Intel 's 8254* series,Broadcom bcm57** series,Marvell 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 25Mhz 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 main function is to boot the computer into the operating system through the server boot . Boot ROM is the boot chip, so that the computer can not have the hard disk, Floppy drive and optical drive, directly through the server power on, 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 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 , there are usually 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 to set the jumper or dip switch to set the IRQ,DMA and I/O port equivalent, and now the network card is using software settings, almost invisible jumper exists. Various network card status and network card information and other data are present in this small eeprom, through it to automatically set up. It records the network card chip supplier ID, 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 bootrom, Whether to enable Bootrom boot system and so on.
9. Data Mercury: This is a device that is available on a consumer-grade PCI network card , and data mercury is also known as a network transformer or a network-isolated transformer. It on a network card on the role of the main two, one is the transmission of data , it sends the PHY out of the differential signal by differential mode coupled with the coil filter to enhance the signal , and by the conversion of the electromagnetic field to the different levels of the connecting cable at the other end; one is to isolate the different levels between different network devices connected by the cable to prevent different voltages from transmitting damaged devices through the cable. 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 LAN). 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 (Ultra 5 standard), respectively, have different use and bandwidth, category is usually referred to as cat, as long as the use of CAT5 specifications of 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, here the bps refers to the bit transmitted per second (1 byte=8 bit). While 100Mbps is called a high-speed Ethernet card (Fast Ethernet), Many are PCI/PCI-E interfaces . Currently on the market, the PCI network has 10/100/1000mbps automatic switching function, according to the network connection environment to automatically adjust the network speed. 1000 Mbps Ethernet is used for high-speed links or backbone between switches or switches and servers.

• 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. The NIC of the ISA interface now uses 16bit bus width, which is characterized by the use of programmed i/ o mode of transmission of data, the transmission must be through the CPU on the I/O through a small window, as a communication between the network card and PC channel, the need to occupy a high CPU utilization, 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.

Note

The 100 identity transfer rate is 100mbit/s, the base identity is transmitted by baseband, t represents the transmission medium, 2 to 5 UTP, and when F, it is represented as optical fiber. X does not have a separate meaning, only represents a faster code name; CSMA/CD (Carrier sense Multiple Access with collision Detection) carrier-monitoring multiplexing (carrier-monitored multipoint access/collision detection) for baseband collision detection. In traditional shared Ethernet, all nodes share the transmission medium. How to ensure the transmission medium is orderly and efficient for many nodes to provide transport services, is the Ethernet media access control protocol to solve the problem.

BNC: ( Bayonet Nut Connector) an RF terminal coaxial cable

Network Port Literacy One: Network card initial understanding (Turn)