Why This Topic is Important for ECET?
Switching techniques form the backbone of data communication and networking. ECET frequently asks questions about circuit, message, and packet switching, because they are directly applied in telecommunication networks, internet routing, and modern communication systems.
By mastering this topic, students can score easily in theory-based and numerical questions that are short, direct, and formula-driven.
📘 Concept Notes
Switching refers to the process of forwarding data from source to destination through intermediate network nodes. There are three major switching techniques:
1. Circuit Switching
- A dedicated physical path is established between sender and receiver before communication.
- Used in telephone networks.
- Phases:
- Establishment (path setup)
- Data transfer
- Release
Advantages: Guaranteed bandwidth, predictable performance.
Disadvantages: Wastage of bandwidth if no data is sent, longer setup time.
Example: Traditional telephone call reserves the circuit even if both users are silent.
2. Message Switching
- Entire message is treated as a single unit and is forwarded from node to node using store-and-forward approach.
- Each intermediate node stores the whole message, then forwards it to the next node.
Advantages: No need for dedicated path, better bandwidth utilization.
Disadvantages: Delay is higher because entire message must be received before forwarding.
Example: Telegraph system, email transfer.
3. Packet Switching
- Message is broken into small packets.
- Each packet carries header (address + sequence info).
- Packets may take different routes and are reassembled at the destination.
Two approaches:
- Datagram Packet Switching – each packet independently routed.
- Virtual Circuit Packet Switching – logical path is established before sending packets.
Advantages: Efficient use of bandwidth, fault-tolerant, faster for bursty traffic.
Disadvantages: Packets may arrive out of order, require reassembly.
Example: Internet data transfer (TCP/IP networks).
⚙️ Formulas
- Transmission delay:
where
= packet length (bits), 
= transmission rate (bps). - Propagation delay:
where
= distance, 
= propagation speed. - Total delay per packet:
End-to-end delay (with N links):
Circuit utilization efficiency:
🔟 10 MCQs
Q1. In circuit switching, the path between sender and receiver is:
a) Dedicated for communication duration
b) Shared among multiple users
c) Not required
d) Dynamic packet-based
Q2. The technique where an entire message is stored at each node before forwarding is:
a) Circuit switching
b) Message switching
c) Packet switching
d) None
Q3. If a 1000-bit packet is transmitted over a 100 kbps channel, transmission delay is:
a) 0.01 s
b) 0.1 s
c) 0.001 s
d) 1 s
Q4. Which switching method is used in Internet communication?
a) Circuit
b) Message
c) Packet
d) None
Q5. The main disadvantage of circuit switching is:
a) Low bandwidth utilization
b) High delay
c) Packet disorder
d) Packet loss
Q6. In message switching, the delay is large because:
a) Each packet waits for acknowledgment
b) Each node must store the complete message
c) Dedicated path setup is required
d) Bandwidth is too low
Q7. If propagation speed = 
m/s and distance = 2000 km, propagation delay is:
a) 0.01 s
b) 0.02 s
c) 0.005 s
d) 0.1 s
Q8. Virtual circuit packet switching combines advantages of:
a) Circuit + Message
b) Circuit + Packet
c) Message + Broadcast
d) Circuit + Broadcast
Q9. If setup time = 2 s and data transfer = 8 s in circuit switching, efficiency is:
a) 20%
b) 50%
c) 80%
d) 100%
Q10. In packet switching, if packet length = 2000 bits, channel rate = 1 Mbps, transmission delay = ?
a) 1 ms
b) 2 ms
c) 0.2 ms
d) 20 ms
✅ Answer Key
| Q No | Answer |
|---|---|
| Q1 | a |
| Q2 | b |
| Q3 | a |
| Q4 | c |
| Q5 | a |
| Q6 | b |
| Q7 | b |
| Q8 | b |
| Q9 | c |
| Q10 | b |
🧠 Explanations
- Q1: Circuit switching dedicates the path → (a).
- Q2: Entire message stored before forwarding → message switching → (b).
- Q3:
→ (a). - Q4: Internet uses packet switching → (c).
- Q5: Circuit switching wastes bandwidth → (a).
- Q6: Each node must store the complete message → (b).
- Q7:
→ (b). - Q8: Virtual circuit = circuit setup + packet transmission → (b).
- Q9:
→ (c). - Q10:
→ (b).
🎯 Motivation / Why Practice Matters
For ECET 2026, network switching questions are direct and formula-based.
- Practicing ensures quick recall of transmission/propagation delay formulas.
- Helps avoid silly mistakes in unit conversions (ms ↔ s, kbps ↔ bps).
- Conceptual clarity gives a competitive edge for scoring marks faster than peers.
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