Exam SY0-401 topic 1 question 20 discussion

Actual exam question from CompTIA's SY0-401

Question #: 20
Topic #: 1

[All SY0-401 Questions]

Which the following flags are used to establish a TCP connection? (Choose two.)

A. PSH
B. ACK
C. SYN
D. URG
E. FIN

Show Suggested Answer

Suggested Answer: BC 🗳️
To establish a TCP connection, the three-way (or 3-step) handshake occurs:
1. SYN: The active open is performed by the client sending a SYN to the server. The client sets the segment's sequence number to a random value A.
2. SYN-ACK: In response, the server replies with a SYN-ACK. The acknowledgment number is set to one more than the received sequence number i.e. A+1, and the sequence number that the server chooses for the packet is another random number, B.
3. ACK: Finally, the client sends an ACK back to the server. The sequence number is set to the received acknowledgement value i.e. A+1, and the acknowledgement number is set to one more than the received sequence number i.e. B+1.
Incorrect Answers:
A: The PSH flag tells the TCP stack to flush all buffers and send any outstanding data up to and including the data that had the PSH flag set.
D: URG indicates that the urgent pointer field has a valid pointer to data that should be treated urgently and be transmitted before non-urgent data.
E: FIN is used to indicate that the client will send no more data.
References:
http://linuxpoison.blogspot.com/2007/11/what-are-tcp-control-bits.html

by Lucky_Alex at March 10, 2020, 4:36 a.m.

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Lucky_Alex

5 years, 3 months ago

1. SYN 2. SYN/ACK 3. ACK

upvoted 1 times

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