12 December 2005

Network Interface Card

Most computers now used for business require a network interface card (NIC), which is responsible for managing the computer's connection to a network.

NICs are used to connect computers to a local area network (LAN). They are obligated to comply with IEEE standards for compatibility, such as the use of a unique 48-bit MAC address assigned to each card; and the Ethernet standard, a type of format that allows >10 million bits per second (Mbps) throughput. Ethernet connections look like a telephone plug, but are somewhat wider.

NIC's are available for laptops, obviously. They connect to a PCMCIA (or PC card) slot.
It is now quite common for networked computers to boot their operating system from the NIC.

Network Interface Cards & Networking Models

Network interface cards are an essential part of the networking data layer. In the 7-layer OSI reference model, the NIC is responsible for handling level-2 data interface. For Ethernet cards, this means that the NIC's role is (a) furnish the crucial media access control (MAC) adresss mentioned above. In each Ethernet data packet (or frame) transmitted, the originating host must include its 6-byte MAC address as well as the destination MAC address. Moreover, the NIC reads the logical link control (LLC) field within incoming frames in order to identify the logical role of the data contained within the packet. One of these fields is the destination service access point (DSAP), which specifies where the packet must be delivered in the receiver's memory; source service access point (SSAP) specifies from where the packet came. This allows multiple protocol stacks to use a single NIC card.

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