10 votes 10 votes Consider the three-way handshake mechanism followed during $\text{TCP}$ connection establishment between hosts $P$ and $Q$. Let $X$ and $Y$ be two random $32$-bit starting sequence numbers chosen by $P$ and $Q$ respectively. Suppose $P$ sends a $\text{TCP}$ connection request message to $Q$ with a $\text{TCP}$ segment having $\text{SYN}$ bit $=1$, $\text{SEQ}$ number $=X$, and $\text{ACK}$ bit $=0$. Suppose $Q$ accepts the connection request. Which one of the following choices represents the information present in the $\text{TCP}$ segment header that is sent by $Q$ to $P$? $\text{SYN}$ bit $=1$, $\text{SEQ}$ number $=X+1$, $\text{ACK}$ bit $=0$, $\text{ACK}$ number $=Y$, $\text{FIN}$ bit $=0$ $\text{SYN}$ bit $=0$, $\text{SEQ}$ number $=X+1$, $\text{ACK}$ bit $=0$, $\text{ACK}$ number $=Y$, $\text{FIN}$ bit $=1$ $\text{SYN}$ bit $=1$, $\text{SEQ}$ number $=Y$, $\text{ACK}$ bit $=1$, $\text{ACK}$ number $=X+1$, $\text{FIN}$ bit $=0$ $\text{SYN}$ bit $=1$, $\text{SEQ}$ number $=Y$, $\text{ACK}$ bit $=1$, $\text{ACK}$ number $=X$, $\text{FIN}$ bit $=0$ Computer Networks gatecse-2021-set2 computer-networks tcp 1-mark + – Arjun asked Feb 18, 2021 • retagged Nov 30, 2022 by Lakshman Bhaiya Arjun 7.0k views answer comment Share Follow See all 2 Comments See all 2 2 Comments reply kumar123 commented Feb 18, 2021 reply Follow Share Answer C: Since sender will send its sQno. x and reciver will send ACK no. x+1 to make sure the sender that i recieved x and send now x+1 Byte SYN bit = 1 for synchronise ACK bit = 1 because reciever giving ackonwledgement to sender, FIN bit = 0 because it is used for termination connection 2 votes 2 votes ronak.ladhar commented Feb 23, 2021 reply Follow Share SYN and FIN consumes one sequence number whereas pure ACK not consumes any sequence number. So by this conclusion we can easily derive that SYN segment sent by P to Q having sequence number X will be consumed and next sequence number of X+1 is expected by the receiver Q. So Q will sent ACK number as X+1 with ACK flag set. Also, it needs to SYN its sequence number so it sends it Y sequence number with its SYN flag set. 0 votes 0 votes Please log in or register to add a comment.
1 votes 1 votes This is related to 3 way handshake where in first handshake, sender send SYN bit. In second handshake reciever sends to sender SYN + ACK bit ( remember here the connection gets established) In third handshake, sender sends ACK bit rish1602 answered Jun 5, 2021 rish1602 comment Share Follow See all 0 reply Please log in or register to add a comment.