I'm an university student majoring in computer science & engineering as a sophomore.

I'm studying about TCP(transport layer) specifically, sequence number. What my materials of Network says sequence number is 'byte stream 'number' of first byte in segment's data'. As I know Operating System decides sequence number randomly but properly.

But I do not understand what 'byte stream number of first byte'.

Is it the value of ID for each byte?


Is it the record saying 'until me(byte), it's n(bytes) of total bytes''?

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    Aug 7, 2017 at 0:26

1 Answer 1


If you consider the TCP session as a stream of bytes, the sequence number is the ordinal number of the first byte in the TCP segment. So the first byte in the first segment is 1. If there are 100 bytes in the segment, the first byte of the second segment will be 101.

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