WHAT IS THE NETWORK INTERFACE CARD (NIC) AND HARDWARE HUB, SWITCH AND ROUTERS

 Network Interface Card (NIC)

Network cards are devices that connect computers to the network. Network cards are both Layer 1 (Physical) & 2 (Data Link) devices as they provide physical access to the medium and also provide physical addressing through the MAC Address. Network Interface Cards are available for desktop, laptop and server computers. A variety of interface such as PCI, Card Bus, USB are available today. Most desktops, laptops, servers and motherboards have Built-in NIC.

 Boot ROM

Normally operating systems are installed on the computer. However, if the computer does not have an operating system installed, you can configure the computer to load an operating system from another computer on its network. To load an operating system from another computer on the network, these computers require a special chip called the BOOT ROM. Boot ROM can be added to the NIC through a special socket or in most cases today, it is often integrated within the NIC. Computers that are not equipped with floppy disk drives or hard disk drives (disk less workstations) to save cost and to keep the network secure, can be used by loading necessary files from a remote computer on a network. Some computers such as public terminals used in libraries, schools, etc. rely on a centralized computer for processing and storing capabilities; referred to as Thin Clients these computers load their operating system and applications from a much powerful computer.

 Hub: Hubs are Physical Layer devices that connect multiple computers. Number of computers that can be connected depends on the number of ports available on a hub, typical 4 to computers. Hubs broadcast data to all devices connected to it leading to collisions; hence they are referred to as multi port repeaters.

 Bridge: Bridge is a device that can connect network segments and separate network traffic based on broadcasts. Bridges examine the frames and selectively transfer frames according to their MAC address. Bridges operate at Layer 2 of the OSI Model.

 Switch: Switch or Network Switch is similar to hub but manage traffic based on MAC address and are efficient in large networks. Switches are considered intelligent as they build a table of MAC Addresses of devices connected to it and when each packet is received, they are analyzed and forwarded to the device with matching MAC Address. Using switches can eliminate collision as each port in the switch acts as a collision domain. Since switches isolate collision domains, they are referred to as multi port bridges. When forwarding frames, switches use Store and forward, cut through, Fragment free or Adaptive switching methods. Unlike a hub that uses half duplex communication, a network switch can send and receive at the same time (full duplex mode) resulting in faster performance. Number of computers that you can connect to a switch depends on the number of ports available (Typically 4 or 8 on SOHO switches designed for use in home and small business networks and 8 – 32 or 64 on switches designed for use in an enterprise network.). The networks can be extended by adding additional switches usually cascaded from the primary switch. Switches designed for larger networks are cascaded through a special port called the Up link port.

 Power over Ethernet

POE describes a standardized system to provide electrical power supply through Ethernet cables; generally, UTP cables carry only signals necessary for data communication. Switches that have support for POE are generally expensive and in some cases only limited number of Ethernet ports are capable of supporting POE. Advantages of POE include the ability to provide power up to 25 watts and distance factor that allows devices to be connected up to 100 meters from the switch.

 Router

Routers are Layer 3 devices that route packets to different logical networks. Routers can discover and transfer packets based on routing table that are predetermined or self discovered. Routing tables are either managed by an administrator by manually defining the routes or automated through special configuration to exchange the routing tables with other routers on a logical network. SOHO Routers are found in home and small business environments and Enterprise Routers are found in ISP’s and enterprise networks.