What is the difference between reliable and unreliable protocols?

What is the difference between reliable and unreliable protocols?

• A. Reliable protocols ensure data is received accurately, while unreliable protocols do not guarantee delivery.
• B. Reliable protocols require encryption; unreliable do not.
• C. Reliable protocols operate only on LAN; unreliable only on WAN.
• D. Reliable protocols use UDP; unreliable use TCP.

Answer: (A)

Reliability in transport protocols is about guarantees of delivery and data integrity. A reliable protocol includes mechanisms to detect errors, acknowledge received data, retransmit lost packets, and preserve the correct order of data. Because of these mechanisms, the receiver is very likely to obtain all data exactly as sent. An unreliable protocol provides best‑effort delivery and does not promise delivery, ordering, or integrity, so some data can be lost, arrive out of order, or be duplicated without automatic correction. Encryption or network type (LAN vs WAN) does not determine reliability, and both kinds of protocols can run over different networks. The common real‑world contrast you’ll see is that a reliable protocol like TCP ensures data is received correctly and in order, while an unreliable protocol like UDP does not guarantee delivery.

Reliability in transport protocols is about guarantees of delivery and data integrity. A reliable protocol includes mechanisms to detect errors, acknowledge received data, retransmit lost packets, and preserve the correct order of data. Because of these mechanisms, the receiver is very likely to obtain all data exactly as sent. An unreliable protocol provides best‑effort delivery and does not promise delivery, ordering, or integrity, so some data can be lost, arrive out of order, or be duplicated without automatic correction.

Encryption or network type (LAN vs WAN) does not determine reliability, and both kinds of protocols can run over different networks. The common real‑world contrast you’ll see is that a reliable protocol like TCP ensures data is received correctly and in order, while an unreliable protocol like UDP does not guarantee delivery.