TCP: Timeout Estimation, Flow Control, and Connection Management

What does TCP use to estimate its timeout interval?

TimeoutInterval = EstimatedRTT + 4 × DevRTT

How does TCP indicate that it has not received an expected segment?

TCP uses duplicate acknowledgments to indicate the absence of an expected segment.

How can TCP detect packet loss before a timeout occurs?

TCP can detect packet loss early by using duplicate acknowledgments.

What is flow control in TCP?

Flow control is a mechanism that prevents a sender from overwhelming a receiver by managing the rate of data transmission based on the receiver's buffer capacity.

What happens when data arrives at a full TCP receive buffer?

If the receive buffer is full, TCP will stop accepting new segments until there is space available.

What does the receive window (rwnd) represent in TCP?

The receive window (rwnd) represents the amount of available space in the receiver's buffer.

How does TCP maintain flow control on the sender side?

The sender tracks the amount of unacknowledged data and ensures it does not exceed the receive window size indicated by the receiver.

What are the two relevant variables maintained by the receiver for flow control?

The receiver maintains LastByteRead and LastByteRcvd.

What does rwnd equal when calculating flow control?

rwnd equals RcvBuffer minus the difference between LastByteRcvd and LastByteRead.

What does a receiver do when its buffer is full and rwnd equals 0?

The receiver sets rwnd to 0 in the header of the last segment sent, indicating no space is available.

How does TCP inform the sender when there is space in the receiver's buffer?

The receiver periodically acknowledges segments with a non-zero rwnd value once space becomes available.

What is the purpose of the SYN segment in TCP connection establishment?

The SYN segment initiates a TCP connection and contains the initial sequence number.

What are the three steps in establishing a TCP connection?

1. Client sends a SYN segment. 2. Server replies with a SYN/ACK segment. 3. Client sends an ACK segment.

What is the role of the FIN segment in closing a TCP connection?

The FIN segment indicates that a host wants to terminate the connection.

What happens when a client sends a FIN segment to the server?

The server acknowledges the FIN, then sends its own FIN segment, followed by an ACK from the client.

What does the RST segment indicate in TCP?

The RST segment indicates that a connection cannot be established or has been reset.

What is the significance of the ACK number in TCP segments?

The ACK number indicates the next expected byte from the other side of the connection.

What is the difference between flow control and congestion control in TCP?

Flow control manages the rate of data transmission based on the receiver's buffer capacity, while congestion control manages the rate based on network conditions.

What happens if a client tries to connect to a closed port?

The server will respond with a TCP RST segment to inform the client that the port is not open.