Local Area Network is a small area network that consist of some computers which are associated with each other with the help of networking medium and also some other nodes are connected in the network such as printer, scanner etc. Here we are going to study some basics of Local Area Network.

IEEE Standards-

IEEE (Institute of Electrical and Electronic Engineers)  is worlds largest technical professional association that promotes engineering and electronic improvement for the benefit of humanity. The IEEE 802 standard is for Local Area Network, Metropolitan Area Network and other area network. The IEEE 802 was started in February 1980. The IEEE 802 committee defines frames, speed, distance and types of cabling to use for networking.

Protocols-

In a network there is some procedure that have to follow for data transmission and they are called as protocols. Protocols are set of rules which are used by the nodes on a network to communicate with each other. Protocols are developed by the committees, different companies and than develop or produce products confirming to those protocols. There some standard protocols of network, which are as follows-

• Ethernet Protocol
• Token Ring Protocol
• ARC net Protocol

IEEE 802/LAN/Ethernet Architecture-

• IEEE 802.3

IEEE 802.3 defines a standard Physical Layer and Data Link Layer of Ethernet architecture that uses wired connection. Ethernet is an architecture that mainly uses BUS topology. IEEE 802.3 defines various cabling that used for different types of topologies.

• IEEE 802.4

IEEE 802.4 defines a standard for Token BUS architecture. Token BUS is similar to Token Ring, but it uses coaxial cables.

• IEEE 802.5

IEEE 802.5 defines a standard for Token Ring architecture. IEEE 802.5 uses 10baseT cabling standard. This architecture uses twisted pair cabling to connect devices instead of coaxial cable. It passes data from one computer to another computer like in a Token BUS network does.

Logical Relationship Of IEEE 802.3 With OSI Reference Model-

Like OSI model of networking the IEEE 802.3 also have layers to communicate on the network. The Physical Layer of the IEEE 802.3 standard is corresponds to the Physical Layer of the OSI model. The Data Link Layer of OSI model is divided into two layers in IEEE 802.3 standard, which are called as Logical Link Control Layer (LLC) and Media Access Control (MAC).

OSI Model	IEEE 802.3
Application Layer	Upper Layer Protocols
Presentation Layer
Session Layer
Transport Layer
Network Layer
Data Link Layer	Logical Link Control
	Media Access Control
Physical Layer	Physical Layer

 

IEEE Defines Ethernet-

As defined by the IEEE the Ethernet standard is 802.3 and this standard is mostly adopted for LAN technology. IEEE 802.3 supports data transfer rates of 10 Mbps, 100 Mbps and 1 GBps. There are three data rate currently define for the operation over Optical Fiber and Twisted Pair cables.

10 Mbps     – 10 Base T Ethernet

100 Mbps   – Fast Ethernet

1000 Mbps – Gigabit Ethernet

Working Of Ethernet Network-

In this network system Ethernet frame is used to transfer data over a network. Each frame defines a Ethernet network is uniquely identified a 48 bit (6 byte) address called Ethernet address. Ethernet address are represented as six pairs of hexadecimal digits separated by a colon.

Elements of Ethernet System
Medium	Set of Media Access Control Rules	Ethernet Frame

 

Ethernet Medium-

Ethernet medium transmits information over the network. Suppose there is a set of computer A, B and D and a printer C. So, if computer D transmits information for printer C, computer B and A also receives the information. All devices connected in this network inspects the destination address. If the received frame in not meant for them, they will reject the frame.

Data Transmission-

When a computer wants to transmit data on the network, it listens to the cable. If two or more devices simultaneously transmit data on an idle cable, collision occurs. Carrier Sense Multiple Access / Collision Detection (CSMA/CD) permits one device to access to the network media at a time to avoid collision.

Networks that are using CSMA/CD technology such as Ethernet network, the devices connected in the network should compete for the network media. Carrier Sensing Multiple Access / Collision Avoidance (CSMA/CA) which is a set of rules that can avoid collision, unlike CSMA/CD that handles network transmission, once collision are detected in CSMA/CD, all devices are forced to wait for a random number of time slots and sense the medium. The medium is sensed to be busy, the device stops the timer until it becomes free again.

Types Of Ethernet (Cabling Standards)-

10 Base 5–

Thick Coaxial cable is used in this network type, so it is also referred to as Thicknet. 10 Base 5 refers to specifications of thick coaxial cable carrying Ethernet signals. The 5 is refers to maximum segment length being 500 meters. RG-8 coaxial cable is used in the network. A 15 pin female DB connector, called AUI connector, is used to connect the device.

10 Base 2-

Thin coaxial cable is used in the 10 Base 2 network. So, it is also referred as Thinnet. In 10 Base 2, “2” refers to approximate maximum segment length of the cable which is 185 meters. 10 Base 2 uses RG 58 coaxial cable with BNC connector.

10 Base T-

In 10 Base T network type allow stations to be attach via twisted pair cable. In 10 Base T the “10” refers to the transmission speed 10 Mbps and “T” refers to twisted pair cable. In a 10 Base T network each computer (node) is connected to a HUB.

10 Base F-

In the 10 Base F network uses the Fiber Optic cable for setup the network. Possesses excellent immunity and is the method of choice when running between buildings or widely separated HUBs. 10 Base F is expensive as the connectors and terminators used in 10 Base F are costly.

Comparing Ethernet Types-

Ethernet Type	10 Base 5	10 Base 2	10 Base T	10 Base F
Media Type	Thick Coaxial	Thin Coaxial	UTP	Fiber Optic
Maximum Segment	500	185	100	1000
Frequency	10	10	10	10
Maximum node per segment	100	30	1024	1024 K

 

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