In a LAN environment, switches improve network efficiency primarily by:
Forwarding frames selectively using MAC addresses
A LAN switch is an intelligent Data Link Layer (Layer 2) device. Unlike an old hub, which simply repeats every incoming bit out of all ports and forces all devices to share one collision domain, a switch makes forwarding decisions based on the Ethernet frame's MAC addresses. This is why the correct answer is that switches improve efficiency by forwarding frames selectively using MAC addresses.
How a switch achieves this:
- It builds and maintains a MAC address table (CAM table) by learning the source MAC address of each frame and the port it arrived on.
- When a frame arrives, it reads the destination MAC, looks it up, and forwards the frame only to the port where that device is connected (unicast) instead of flooding every port.
- Each switch port forms its own collision domain, so devices can communicate in parallel, often in full-duplex mode with no collisions.
The result is that each link carries mostly its own intended traffic, giving higher effective throughput and far fewer collisions.
Why the other options are wrong:
- Broadcasting all frames to every device describes hub behaviour, which wastes bandwidth — it is the very inefficiency switches were designed to eliminate (a switch floods only for unknown-unicast or genuine broadcast frames).
- Increasing collisions and retransmitting is the opposite of a switch's purpose; by segmenting collision domains it reduces collisions.
- Converting digital to analog signal is the function of a modem, not a switch, and has nothing to do with frame forwarding.
Important Questions from Data Link Layer
Which of the following protocols is responsible for converting higher level protocol addresses to physical network addresses?
Which of the following devices takes data sent from one network device and forwards it to the destination node based on MAC address?
Which of the following statements is/are true with regard to various layers in the Internet stack?
P: At the data link layer, a packet of transmitted information is called a frame
Q: At the network layer, a packet of transmitted information is called a segment
Given below are two statements:
Statement I: The laws of nature put two fundamental limits on data rate of a channel. The H.Nyquist limit restricts the number of independent samples per second to twice the band-width in a Noiseless channel.
Statement II: Shannon's major result about noised channel is that maximum data rate of a channel whose band width is H Hz, and whose signal-to-noise ratio is S/N is given by:
Maximum number of bits/sec \(= H \;log_2 \left(1+\frac{S}{N}\right)\) is given by:
In the light of the above statements. choose the correct answer from the options given below
Which of the following statements are true?
(a) Three broad categories of Networks are:
(i) Circuit Switched Networks
(ii) Packet Switched Networks
(iii) Message Switched Networks
(b) Circuit Switched Network resources need not be reserved during the set up phase.
(c) In packet switching there is no resource allocation for packets.
