Why can't a reliable protocol be built over UDP like TCP?
sobes.tech AI
Answer from AI
UDP is a connectionless protocol that does not guarantee delivery, order, or data integrity. Unlike TCP, it does not provide:
- acknowledgment of packet receipt (ACK)
- flow control
- congestion control
- packet ordering
Building a reliable protocol on top of UDP is theoretically possible, but practically very difficult and inefficient because:
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Implementation complexity: You need to implement all mechanisms already built into TCP — acknowledgments, retransmissions, sequence control, congestion management.
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Performance and resources: Such mechanisms require additional logic and resources, which can degrade performance.
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Support and debugging complexity: A custom protocol over UDP is harder to test and maintain.
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Lack of standardization: TCP is a standardized protocol with proven algorithms, whereas a homemade protocol may have vulnerabilities and instability.
Therefore, if reliable delivery and order are needed, TCP is usually used. UDP is applied in tasks where speed is crucial and packet loss is acceptable (e.g., streaming, gaming), or specialized protocols over UDP are used, such as QUIC, which implements reliability and security but is a complex and carefully designed protocol.