Although other network technologies axist,Ethernet has achieved near-ubiquity since themid-1990s.Every Ethernet network card has a unique 48-bit serial number called a MAC address,which is stored in ROM carried on the card.Every computer on an Ethernet network must have a card with a unique MAC address.Normally it is safe to assume that no two network cards will share the same address,because card vendors purchase blocks of addresses from the institute of electrical and electronics engineers and assign a unique address to each card at the time of manufacture.
Whereas network cards to be expansion cards thet plug into a computer bus,the low cost and ubiquity of the Ethernet standard means that most newer computers have a network interface build into the motherboad.These either have Ethernet capabilities integrated into the motherboad chipset or implemented via a low cost dedicated Ethernet chip,connected through the PCI.A separate network card is not required unless multiple interfaces are needed or some other type network is used.Newer motherboad may even have dual network interfaces built-in.
There are four techniques used to trasfer data,the NIC may use one or more of these techniques.
- Polling is where the microprocessor examines the status of the peripheral under program cuntrol.
- Programmed I/O is where the microprocessor alerts the designated peripheral by appliying its address to the system's address bus.
- Interrupt-driven I/O is where the peripheral alerts the microprocessor that it's ready to trasfer data.
- DMA is where the inteligent peripheral assumes cont
