Cable And Adapter The Physical Connection
The communication adapter is also known as the network adapter or network Interface Card, but now more people are willing to use the simpler name "network Card". Mainly used to connect the Shared resources, is the necessary parts of computer system.
The physical connection
Insert a network interface board (or insert a PCMCIA card into a laptop) in the mainframe box to connect the local computer to the external network.
Network card is working in the data link layer of the network components, is connected to the computer and transmission Cable and Adapter The physical connection
medium in the LAN interface, not only can realize the physical connection between a local area network transmission medium and electrical matching, still involve the sending and receiving of frame, frame encapsulation and unpacking, media access control, data coding and decoding, and the function of the data cache, etc.
Network card function
The network card is equipped with processors and memory (including RAM and ROM). Network and local area network (LAN) via cable or twisted-pair cable is the communication between, on the basis of serial transmission and network card and computer communications between is through computer motherboard in parallel I/O bus transfer manner. Therefore, one of the important functions of nic is to perform serial/parallel conversion. Because the data rate on the network is not the same as the data rate on the computer bus, there must be a memory chip that is stored in the network card.
When installing a network card management nic device driver must be installed in the computer operating system, the driver will tell after card, should from the memory of what position will LAN sent a block of data storage. Network card also can realize Ethernet protocol.
Nic is not independent of autonomous units, because the card itself with no power but must use the inserted the power of the computer, and controlled by the computer, so nic to see be a semi-autonomous units. When a network card receives a wrong frame, it discards the frame without notifying the computer it has inserted. When a network card receives a correct frame, it USES an interrupt to notify the computer and deliver it to the network layer in the protocol stack. When a computer wants to send an IP data message, it is sent down from the protocol stack to the network card and sent to the LAN.
With the continuous improvement of integration, the number of chips on the card is constantly decreasing, although there are many kinds of network CARDS produced by each manufacturer now, but the functions are similar. The main functions of network card are as follows:
1. Encapsulation and unsealing of data: the data that is handed down from the previous layer will be added to the first and the tail, which will be the frame of Ethernet. The Ethernet frames are stripped to the first and the tail, then sent to the upper layer;
2. Link management: mainly the implementation of CSMA/CD protocol;
3. Coding and decoding: Manchester coding and decoding.
In terms of compatible network card, currently, the network card is generally divided into common station network card and server special network card. Dedicated server nic is suit sort is more, in order to adapt to network performance also have differences, can be classified according to the following standards: according to the poor support different bandwidth can be divided into 10 m card, 100 MB card, 10/100 m adaptive network card, the card several of 1000 m; According to the different types of network card bus, there are three main categories of ISA network card, EISA network card and PCI network card, of which ISA network card and PCI network card are used more frequently. The bandwidth of the ISA bus network card is generally 10M, and the bandwidth of the PCI bus network card is from 10M to 1000M. Also the 10M network card, because the ISA bus is 16, and the PCI bus is 32-bit, so the PCI network card is faster than the ISA network card.
The interface type of network card: according to the transmission medium, the network card has the AUI interface (coarse cable interface), BNC interface (fine cable interface) and rj-45 interface (double stranded interface). Therefore, when choosing a network card, you should pay attention to the type of interface supported by the card, otherwise it may not apply to your network. The 10M network CARDS commonly used in the market mainly include a single network card (rj-45 interface or BNC interface) and a double-port network card (rj-45 and BNC), with less network card with AUI coarse cable interface. The 100mb and 1000M network CARDS are usually called single card (rj-45). In addition to the network card interface, we often have to pay attention to whether the network card supports no disk start. Also consider whether the network card supports fibre connection when necessary.