Question

A developer is designing a network application. She needs reliable delivery of messages with error checking, sequencing, and acknowledgment, but another part of her application needs fast transmission of data without delay, and occasional data loss is acceptable. Identify the protocols should she use for the above two cases?

• A. Use TCP for reliable delivery, and UDP for fast, unreliable transmission.
• B. Use UDP for reliable delivery, and TCP for fast, unreliable transmission.
• C. Use TCP for both reliable and fast transmission.
• D. Use UDP for both cases because it’s faster than TCP.

Hint:

TCP = "Phone Call" (Must establish connection, both must hear).
UDP = "Postcard" (Send it and hope it arrives; much faster but no confirmation).

Answer 1

The Correct Option is A

Concept:
In the Transport Layer of the OSI/TCP-IP model, two primary protocols provide different types of services: TCP (Transmission Control Protocol) and UDP (User Datagram Protocol). Choosing between them is always a trade-off between Reliability and Speed.

Step 1: Analyzing Case 1: Reliable Delivery.
The developer needs: Error checking, Sequencing (packets arrive in order), and Acknowledgments (sender knows data arrived).
• TCP provides all these through a "Connection-oriented" service. It uses a 3-way handshake to establish a link and re-transmits data if an ACK is not received. This is ideal for file transfers or web browsing.

Step 2: Analyzing Case 2: Fast Transmission.
The developer needs: Speed, no delay, and can tolerate data loss.
• UDP is "Connectionless" and "Best-effort." It doesn't use handshakes or acknowledgments. It simply sends the data ("Fire and forget"). While some packets might get lost or arrive out of order, there is no delay caused by waiting for re-transmissions. This is ideal for video streaming or gaming.

Step 3: Conclusion.
Based on these requirements, the developer must use TCP for the first part of the application and UDP for the second part. This hybrid approach is common in modern applications (e.g., VoIP uses TCP for signaling and UDP for the actual voice data).