Question
Consider the following statements.
I. TCP connections are full duplex
II. TCP has no option for selective acknowledgement
III. TCP connections are message streams
Which of the following is correct?
Official answer and solution
- Official answer
- A
- From
- Official GATE 2015 answer key
Solution
Analyze each statement regarding TCP protocol properties.
Evaluate the statements:
- Statement I: "TCP connections are full duplex"
TCP allows both communicating endpoints to send and receive data simultaneously over the same connection, maintaining independent sequence numbers and buffers for each direction. This is a core property of TCP. Statement I is true.
- Statement II: "TCP has no option for selective acknowledgement"
RFC 2018 defines the TCP Selective Acknowledgement (SACK) option, allowing a receiver to inform the sender of all segments received correctly, so only missing segments need retransmission. Thus, the statement that TCP has no such option is false.
- Statement III: "TCP connections are message streams"
TCP provides a byte-stream service, treating application data as a continuous stream of unstructured bytes without preserving message boundaries. Protocols like UDP provide message-oriented / datagram service. Thus, Statement III is false.
Therefore, only Statement I is correct (Option A).
Final answer
A
Common trap
Confusing TCP's byte-stream orientation with message streams, or unawareness of the SACK TCP option.
The answer is the one in the official GATE answer key. The solution is this site's own explanation.
Source
- Paper
- GATE 2015 Computer Science and Information Technology (CS) Session 3
- Question
- 32 of 65, printed as CS Q.22
- Section
- Computer Science and Information Technology
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