What is Nagle's algorithm and when is it beneficial?

• A. It buffers small outgoing segments to reduce small-packet overhead and is especially beneficial for interactive, character-by-character input.
• B. It buffers small outgoing segments to reduce small-packet overhead; it may introduce latency for frequent small writes.
• C. It disables buffering and sends each segment immediately.
• D. It applies to UDP streams to optimize reliability.

Answer: (B)

Nagle's algorithm is a TCP optimization that buffers small outgoing data and waits to send it as a larger segment, reducing the overhead of many tiny packets on the network. It holds back new data until either an earlier segment is acknowledged or enough data has accumulated to fill the maximum segment size, then sends a bigger chunk. This improves efficiency when an application writes lots of small pieces but doesn’t need immediate delivery. However, that buffering can add latency for frequent small writes, because each piece may wait for the next send opportunity to merge with others. It’s a TCP mechanism, not something that applies to UDP, and if you need immediate transmission for low-latency interactions you’d disable it, which loses the overhead savings. That's why this description—buffering small outgoing segments to reduce small-packet overhead, with potential latency for frequent small writes—is the best fit.