A NIC (network interface card) is designed to communicate over a computer network. It allows users to connect to each other through the use of cables or wirelessly if the network card is a wireless network card (Wi-Fi / WNIC). Each entity of a network, a computer, a printer, router, etc., who need to communicate with other devices must have a network card if it is to communicate through the network. On older computers, the network card is probably an expansion card, usually PCI or PCI Express. high-performance cards can cost less than $ 30. NIC functionality is now often integrated into the motherboard chipset or implemented with a dedicated Ethernet chip on the motherboard.
A similar situation applies to laptops. At one time, a PCMCIA network card would be used in a laptop for the NIC as the PCI card has been used in desktop computers, but now, NIC functionality is often integrated with the motherboard.
Ethernet is the dominant standard for cable connections for wired networks. An Ethernet connector is similar to a telephone jack, only bigger. This connector is called "RJ45". Ethernet cables are shielded or unshielded cable of four twisted pairs of 24 AWG connectors, indicated at 100 ohms. Maximum cable length for CATx cable is 100 meters.
The first versions of Ethernet cables were CAT3 or CAT4 (CAT being short for category). These versions were not long-lived. CAT5 and CAT5e are currently the most commonly used cables (bandwidth of 100 MHz, 100 Mbps), with CAT6 (bandwidth of 250 MHz, 1 Gbps) and the near future conditions. A cable CAT7 (bandwidth 0 MHz) specification is being developed, and should be available within a few years.
Every Ethernet network card has a unique serial number called a "media access code" (MAC address) that is used to identify the network card and associated computer on the network. No two NICs will have the same address, because the NICs manufacturers must buy blocks of addresses by the Institute of Electrical and Electronics Engineers (IEEE).
NICs are capable of different speeds. Speeds up to one gigabit per second (Gbps) are now available. Two NIC can communicate if they differ in speed ratings, but will communicate to the slower rate of NIC.
In a simple network, NIC can be used to connect a personal computer (PC). If computers are connected directly to each other, the network is a "peer-to-peer" (P2P, also called "ad hoc") network. If computers are connected directly to each other, a "crossover" Ethernet cable is required (also called a "null modem cable"). This cable is not "straight-through", as standard Ethernet, but passes through the sending and reception, so that the transmission line from computer A is connected to the receive line of the computer B.
For the networks of some computers, a "hub" can be used with all computers connected to the hub. Each message sent from any PC will be seen by all computers, but only the computer with the correct MAC address will receive the message. P2P networks are useful for many purposes. Sharing files and printers are the most common applications.
networks with more than four active computers at a time will be eligible to use a "network switch" instead of a hub. A mains switch will direct the message to the appropriate destination, instead of each message packet transmitted over the network. A computer can send a message to computer B, simultaneously, computer C sends a message to computer D. This increases network efficiency. This is a simple form of a network of servers. An example of a client-server design is a computer server that the client to initiate a download or upload files, and the server responds. The server also often the task to interact with printers and other servers on other networks, including satellite networks (SATCOM) or Internet.
"latency" is the delay caused by a data communication network. Latency causes not only the slow service, but may cause the loss of data as well. Latency is usually tested by sending a message packet that is immediately returned to the sending computer. The round-trip time is defined as the latency.
network performance can be optimized for both latency and throughput. The networks can use a technique known as "interrupt moderation" to increase throughput and reducing CPU utilization by the message packets queue and the emission of a smaller number of interrupts to the CPU. A network optimized in this way would favor large transfers, reducing the transfer load. CPU and benefit from network throughput, but the increase of network latency. The alternative is to fragment each message and pipeline fragments through the network. Multiple paths from source to destination may allow overlapping. Latency can also be dealt with techniques such as prefetching (anticipating the need to requests for data) and / or that use multiple execution threads (multithreaded).
There are two signaling LED on a typical network adapter. A single green LED indicates that the computer connected to the network. This is called the light "link". The second LED is amber in color. A blinking amber LED indicates a message packet collisions are occurring. occasional collisions are normal on a busy network, but frequently lit amber LED is an indication of problems. A quick link LED (green flash) is a network activity indicator, which means that communication is ongoing. If the green link light is off, and the amber LED is blinking, then the network card is in "Power Save" mode.
A wireless network interface controller (WNIC) is a network card to connect to a wireless network (WiFi). The standard for WiFi IEEE 802.11. A WNIC uses an antenna to communicate with an RF signal, most of the times at 2.4 GHz. The development of wireless connectivity in recent years has narrow parallel wired connectivity. Like its wired cousin, a wireless card was once integrated with a PCI or PCMCIA add-on. Now, it integrated WNIC are becoming common, especially for laptops.
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