The LAN connections are of numerous types among those Ethernet is the one that is the most popular LAN connection. The generation of Ethernet took place in the following direction-:
1. Traditional Ethernet
2. Fast Ethernet
3. Gigabit Ethernet
In 1976 the traditional Ethernet was created having a data rate of 10 mbps and fast internet the next version has a speed of 100 mbps where as the gigabit has a speed of 1000 mbps.
As the computer is connected to the internet through the LAN then it needs all the five models of the internet model where the network transport and application layer are used for each and every LAN .
The data link layer is basically divided into two layers -:
• Logic link control
• Medium access control
The MAC sub layer can be abbreviated as medium access control sub layer.The MAC sub layer governs the operation of the access methodology it also frames the data received from the upper layer and passes it to the sub layer for encoding.
The basic unit of Bluetooth is piconet and a piconet contains a master node and up to seven active slave nodes and a collection of piconet connected by a bridge node in a large room is known as scarnet.
A Bluetooth standard allows a maximum of 255 packed nodes in addition to 7 slave nodes the parked nodes are the devices that the masters has switched to low power state to reduce power drain.
All the communications are to be done by master and slave a slave- slave communication is not possible.
IEEE STANDARDS AND ITS CHANGES
1. 802.11-:In 1997 the Institute of Electrical and Electronics Engineers created the first WLAN and called it 802.11 Unfortunately the 802.11 only supported a maximum network bandwidth of 2 Mbps which is too slow for most of the applications so the 802.11 wireless products are neither manufactured nor used any longer .
2. 802.11b-: IEEE expanded the original 802.11 standard in the year 1991 creating the 802.11b. 802.11b supports a bandwidth of maximum 11 Mbps, comparable to traditional Ethernet. 802.11b also uses the same unregulated radio signaling frequency of2.4 GHz as it is preferred to lower the production costs.
3. 802.11a-:After 802.11b was developed the IEEE created a second extension to the original 802.11 standard the 802.11a and this supports a bandwidth up to 54 Mbps and signals in a regulated frequency of 5 GHz.
4. 802.11g-: In 2002 and 2003 a newer standard called 802.11g emerged on the market. 802.11g combines the best of both 802.11a as well as 802.11b.
5. 802.11n-:The newest IEEE standard in the Wi-Fi category is 802.11n. It was designed to improve on 802.11g in the amount of bandwidth supported by utilizing multiple wireless signals and antennas (called MIMO technology) instead of one.
IEEE 802.11- Architecture
The IEEE 802.11 corresponds to OSI physical layer. It is divided into two layers -:
• Mac sub layer- this layer solves the channel allocation problem
• LLC sub layer-this layer interact with the network layer
The ieee standard consist of three frames –
• Data frame
• Control frame
• Management frame
QUESTIONS AND ANSWERS
1.State the difference between half duplex and full duplex transmission modes?
Ans- in case of half duplex only one entity can be sent at a time where as in full duplex more than one entity can be sent at a time.
2. What are the five components of data system?
Ans- The five components of a data communication system are sender,receiver,transmission,medium,message and protocol.