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312-50V9 · Question #300

The establishment of a TCP connection involves a negotiation called 3 way handshake. What type of message sends the client to the server in order to begin this negotiation?

The correct answer is D. SYN. The TCP 3-way handshake begins when the client sends a SYN segment to signal its intent to establish a connection and share its initial sequence number.

Scanning Networks

Question

The establishment of a TCP connection involves a negotiation called 3 way handshake. What type of message sends the client to the server in order to begin this negotiation?

Options

  • ARST
  • BACK
  • CSYN-ACK
  • DSYN

How the community answered

(45 responses)
  • A
    7% (3)
  • B
    4% (2)
  • C
    2% (1)
  • D
    87% (39)

Why each option

The TCP 3-way handshake begins when the client sends a SYN segment to signal its intent to establish a connection and share its initial sequence number.

ARST

RST (reset) is used to abruptly terminate an existing or invalid connection, not to initiate one.

BACK

ACK (acknowledge) confirms receipt of data and is the third and final step of the handshake, not the initiating step.

CSYN-ACK

SYN-ACK is the server's second-step response to the client's initial SYN, not the message that begins the negotiation.

DSYNCorrect

SYN (synchronize) is the very first segment sent by the client to the server, carrying the client's initial sequence number and requesting connection establishment. This triggers the server to reply with SYN-ACK, after which the client sends a final ACK to complete the handshake.

Concept tested: TCP 3-way handshake connection initiation

Source: https://www.rfc-editor.org/rfc/rfc793

Topics

#TCP SYN#three-way handshake#connection initiation#TCP/IP

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