LAN CARD

A Local Area Network (LAN) card is used to provide wireless Internet access to computer users in home or roaming networks. It works by exchanging signals with a router, which transmits the signals over a physically wired line. The LAN card became ubiquitous in Western society in the early part of the twenty first century, when the cards became affordable due to wireless networks springing up everywhere, from coffee shops to airports.
Most home Internet users use a LAN card for wireless Internet access so that multiple residents can be on the Internet at the same time. The router is placed in a central location in the home to provide even signal across the household. Wireless networks are also widespread on college campuses, so that students with laptops can use the Internet wherever they may be. The value of wireless to attract customers has been recognized by restaurants and other such businesses, who usually provide network access in exchange for a small fee or purchase of their product.
A LAN card communicates with the router using radio waves and an antenna. The computer converts data into binary form and sends it to the LAN card, which in turn broadcasts the signal to be picked up by the router. The router sends the information on in the form of packets of information, and bundles information for return to the computer via the LAN card in the same way. Usually wireless networks transmit at a relatively high frequency, ranging between 2.4 and 5Ghz, designed to accommodate the more rapid transfer of large amounts of data. When purchasing a router or LAN card, the packaging will indicate the frequency of the signal it uses.
A network card, network adapter, network interface controller (NIC), network interface card, or LAN adapter is a computer hardware component designed to allow computers to communicate over a computer network. It is both an OSI layer 1 (physical layer) and layer 2 (data link layer) device, as it provides physical access to a networking medium and provides a low-level addressing system through the use of MAC addresses. It allows users to connect to each other either by using cables or wirelessly.

Although other network technologies exist, Ethernet has achieved near-ubiquity since the mid-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 (IEEE) and assign a unique address to each card at the time of manufacture.
Whereas network cards used to be expansion cards that plug into a computer bus, the low cost and ubiquity of the Ethernet standard means that most newer computers have a network interface built into the motherboard. These either have Ethernet capabilities integrated into the motherboard chipset or implemented via a low cost dedicated Ethernet chip, connected through the PCI (or the newer PCI express bus). A separate network card is not required unless multiple interfaces are needed or some other type of network is used. Newer motherboards may even have dual network (Ethernet) interfaces built-in.
The card implements the electronic circuitry required to communicate using a specific physical layer and data link layer standard such as Ethernet or token ring. This provides a base for a full network protocol stack, allowing communication among small groups of computers on the same LAN and large-scale network communications through routable protocols, such as IP.
There are four techniques used to transfer data, the NIC may use one or more of these techniques.
• Polling is where the microprocessor examines the status of the peripheral under program control.
• Programmed I/O is where the microprocessor alerts the designated peripheral by applying its address to the system's address bus.
• Interrupt-driven I/O is where the peripheral alerts the microprocessor that it's ready to transfer data.
• DMA is where the intelligent peripheral assumes control of the system bus to access memory directly. This removes load from the CPU but requires a separate processor on the card.
A network card typically has a twisted pair, BNC, or AUI socket where the network cable is connected, and a few LEDs to inform the user of whether the network is active, and whether or not there is data being transmitted on it. Network Cards are typically available in 10/100/1000 Mbit/s varieties. This means they can support a transfer rate of 10, 100 or 1000 Megabits per second.

Multiple users can maintain a connection to the router on different bands, to avoid interference, and are assigned unique identities by the router in the form of an IP address. Each user attempting to access the network will need a LAN card, which is either available built into the computer or as an external attachment which can be connected through a Universal Serial Bus port or PC card slot in a laptop.
Networks have a variety of security settings, with some being accessible to all users and other requiring a password to access the router. Even when a network is secured, a LAN card will be able to see it and list it as an available network, but when asked to connect will prompt the user for a password. It is recommended that wireless networks be secured to prevent the exploitation of vulnerabilities, and that users never connect to an unknown network.
A Network Interface Controller (NIC) is a hardware interface that handles and allows a network capable device access to a computer network such as the internet. The NIC has a ROM chip that has a unique Media Access Control (MAC) Address burned into it. The MAC address identifies the vendor MAC address which identifies it on the LAN. The NIC exists on both the ' Physical Layer' (Layer 1) and the 'Data Link Layer' (Layer 2) of the OSI model.
Sometimes the word 'controller' and 'card' is used interchangeably when talking about networking because the most common NIC is the Network Interface Card. Although 'card' is more commonly used, it is less encompassing. The 'controller' may take the form of a network card that is installed inside a computer, or it may refer to an embedded component as part of a computer motherboard, a router, expansion card, printer interface, or a USB device.
A MAC Address is a 48 bit network hardware identifier that is burned into a ROM chip on the NIC to identify that device on the network. The first 24 bits is called the Organizationally Unique Identifier (OUI) and is largely manufacturer dependent. Each OUI allows for 16,777,216 Unique NIC Addresses.
Smaller manufacturers that do not have a need for over 4096 unique NIC addresses may opt to purchase an Individual Address Block (IAB) instead. An IAB consists of the 24 bit OUI, plus a 12 bit extension (taken from the 'potential' NIC portion of the MAC address)
A wireless network interface controller (WNIC) is a network card which connects to a radio-based computer network, unlike a regular network interface controller (NIC) which connects to a wire-based network such as token ring or ethernet. A WNIC, just like a NIC, works on the Layer 1 and Layer 2 of the OSI Model. A WNIC is an essential component for wireless desktop computer. This card uses an antenna to communicate through microwaves. A WNIC in a desktop computer usually is connected using the PCI bus. Other connectivity options are USB and PC card. Integrated WNIC's are also available, (typically in Mini PCI/PCI Express Mini Card form).
A WNIC can operate in two modes known as infrastructure mode and ad hoc mode.
In an infrastructure mode network the WNIC needs an access point: all data is transferred using the access point as the central hub. All wireless nodes in an infrastructure mode network connect to an access point. All nodes connecting to the access point must have the same service set identifier (SSID) as the access point, and if the access point is enabled with WEP they must have the same WEP key or other authentication parameters.
In an ad-hoc mode network the WNIC does not require an access point, but rather can directly interface with all other wireless nodes directly. All the nodes in an ad-hoc network must have the same channel and SSID.
WNICs are designed around the IEEE 802.11 standard which sets out low-level specifications for how all wireless networks operate. Earlier interface controllers are usually only compatible with earlier variants of the standard, while newer cards support both current and old standards.

Specifications commonly used in marketing materials for WNICs include:
• Wireless data transfer rates (measured in Mbit/s); these range from 2 Mbit/s to 54 Mbit/s.[1]
• Wireless transmit power (measured in dBm)
• Wireless network standards (may include standards such as 802.11b, 802.11g, 802.11n, etc.) 802.11g offers data transfer speeds equivalent to 802.11a – up to 54 Mbit/s – and the wider 300-foot (91 m) range of 802.11b, and is backward compatible with 802.11b.
Wireless local area network standards
802.11
Protocol Release[2]
Freq.
(GHz) Typ throughput
(Mbit/s)
[citation needed]
Max net bitrate
(Mbit/s) Modulation rin.
(m) rout.
(m)
–
Jun 1997 2.4 00.9 002 IR/FH/DSSS ~20 ~100
a
Sep 1999 5 23 054 OFDM
~35 ~120
b
Sep 1999 2.4 04.3 011 DSSS
~38 ~140
g
Jun 2003 2.4 19 054 OFDM
~38 ~140
n
~ Jun 2010 2.4
5 74 300 OFDM
~70 ~250[3]

y
Nov 2008 3.7 23 054 OFDM
~50 ~5000