LAN Technologies MCQ Quiz in தமிழ் - Objective Question with Answer for LAN Technologies - இலவச PDF ஐப் பதிவிறக்கவும்

CSMA (Carrier Sense Multiple Access) is a Media Access Control (MAC) protocol that is used to control the flow of data in a transmission media so that packets do not get lost and data integrity is maintained.

There are two modifications to CSMA:

• CSMA CD (Collision Detection)
• CSMA CA (Collision Avoidance)

 

• IEEE 802.11 wireless LANs us a media access control protocol called Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA).
• Unlike CSMA/CD (Carrier Sense Multiple Access/Collision Detect) which deals with transmissions after a collision has occurred, CSMA/CA acts to prevent collisions before they happen.
• In CSMA/CA, as soon as a node receives a packet that is to be sent, it checks to be sure the channel is clear, i.e. no other node is transmitting at the time). 
• If the channel is clear, then the packet is sent. If not, the node waits for a randomly chosen period of time and then checks again to see if the channel is clear.

The correct option is 48 bits.

CONCPET:

The MAC address is a unique 12-digit hexadecimal numbers (48 bits in length) hardware address associated with a network adapter card, which is engraved on NIC at the time of manufacturing.

They can be physically identified on the network using its MAC address is a permanent address and cannot be changed under any circumstances it means two devices cannot have the same MAC address.

It is 12-digit hexadecimal numbers (48 bits in length) format on each device and is represented by Colon-Hexadecimal notation.

Example: 00:0b:45:9e:87:46.

Data:

Length of cable(D) = 3km

Bandwidth (BW) = 30 MB/s

Speed = V = 2.5 × 108 m/s = 2.5 × 105 km/s

Frame size = Lmin 

Formula:

For CSMA/CD

​\({T_t} \ge 2 \times {T_p}\)​

Calculation:

\({T_t} \ge 2 \times {T_p}\)

\(L \ge 2 \times {T_p} \times BW\)

\({L} \ge 2 \times \frac{D}{V} \times BW\)

\({L} \ge 2 \times \frac{3}{2.5\times10^5} \times 30 \times10^6 \;bytes\)​​

 Lmin = 720 bytes = 5760 bits

• A point-to-point connection provides a dedicated link between two devices
• In mesh, star and ring topologies are point-to-point connection
• In a star topology, each device needs only one link and one I/O port to connect it to any number of other devices
• In a ring topology, each device has a dedicated point-to-point connection with only the two devices on either side of it; Each device is connected to its corresponding repeater
• In a mesh topology, every device has a dedicated point-to-point link to every other device
• A multipoint connection is one in which more than two specific devices share a single link
• In Bus Topology, one long cable acts as a backbone to link all the devices in a network

Here, the processor refers to system or devices operating.

Location	Network	Range
City	MAN (Metropolitan Area Network)	10 km-100 km
Country	WAN (Wide Area Network)	100 km-1000 km
Campus	LAN (Local Area Network)	Around 1 km

 Key Points

• It is a computer network within a small geographical area.
• A LAN is composed of interconnected workstations and personal computers which are each capable of accessing and sharing data and devices, such as printers, scanners and data storage devices, anywhere on the LAN.

MAC destination	MAC Source	VLAN tag (Optional)	Frame Length	Payload	Frame Check Sequence (CRC)
6 Byte	6 Byte	2 Byte	2 Byte	46-1500 Byte	4 Byte

 

MAC broadcast address (MAC destination) consists of 6 bytes i.e. 48 bits and all are 1’s

MAC broadcast address → FF:FF:FF:FF:FF:FF

Limited broadcast address (IP-32 bit) → 255.255.255.255

Institute of Electrical and Electronics Engineers (IEEE): The Institute of Electrical and Electronics Engineers is the largest professional engineering society in the world. International in scope, it aims to advance theory, creativity, and product quality in the fields of electrical engineering, electronics, and radio as well as in all related branches of engineering. IEEE oversees the development and adoption of international standards for computing and communications.

To solve the looping problem, the bridges use the spanning tree algorithm to create a loop less topology. A spanning tree is a graph in which there is no loop. In a bridged LAN, this means creating a topology in which each LAN can be reached from any other LAN through one path only (no loop). We cannot change the physical topology of the system because of physical connections between cables and bridges, but we can create a logical topology that overlay the physical one.

Answer: Option 4

Concept: 

There are generally 5 types of communication channels in computer network

1. Twisted pair cables: 

• Signals are transmitted using pairs of independently insulated wires that have been physically twisted together.
• Used by older telephone networks.
• transmit signals in form of Electric current.

2.  Coaxial cables:

• It consists of two concentric conductors separated by a dielectric material.
• High-frequency signals can be carried on a single cable – used for video transmission.

3. Fibre Optic Cables:

• Digital signals are sent as light pulses which are translated back into electrical signals.
• The Centre core is composed of a Fine glass strand surrounded by glass cladding and a protective layer.

​4. Terrestrial Stations:

• Information is sent via microwaves from ground-based transmitting and receiving stations.
• Microwave stations (a.k.a. repeater stations)  must be placed every 50 kilometres to receive, amplify, and then pass the signal along.

Explanation: 

Twisted pair cables transmit signals in form of Electric current.

• In star topology, each device needs only one link and one I/O port to connect it to any number of other devices
• In mesh topology, each device is connected to each other directly by a link
• In full duplex mode with ‘n’ nodes are present then number of links needed is (n× (n-1)) ÷ 2) Therefore, wiring required in case of mesh topology is more than the star topology, also installation cost is more which makes it expensive which means star topology is less expensive.