CODEWITHSUNDEEP
tcp
tpm900
tpm900

Reputation: 271

If an ACK packet is lost will a SYN packet be resent with the same sequence number?

Supposed an ACK packet is lost in transmission, and after that timeout, the original packet is resent. Will this duplicate packet contain the same sequence number?

Upvotes: 2

Views: 931

Answers (2)

Nan Xiao
Nan Xiao

Reputation: 17467

I think the resent SYN should have different ISN (Initial Sequence Number). The following words are from 13.2.3 Initial Sequence Number (ISN), TCP/IP Illustrated, Volume 1:

Before each end sends its SYN to establish the connection, it chooses an ISN for that connection. The ISN should change over time, so that each connection has a different one. [RFC0793] specifies that the ISN should be viewed as a 32-bit counter that increments by 1 every 4μs. The purpose of doing this is to arrange for the sequence numbers for segments on one connection to not overlap with sequence numbers on a another (new) identical connection. In particular, new sequence numbers must not be allowed to overlap between different instantiations (or incarnations) of the same connection.

Upvotes: 0

Palash Borhan Uddin
Palash Borhan Uddin

Reputation: 394

Yes, this will have same sequence number for the retransmission.

Upvotes: 1

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