GSLC-2020: GIAC Security LeadershipDemo

By GIAC · Question Mode

QuestionQ294

Networking Concepts for Managers

A sequence number is a 32-bit value ranging from 1 to 4,294,967,295. When data is transmitted across a network, it is split into fragments (packets) at the source and reassembled at the destination system. Each packet includes a sequence number that the destination system uses to reconstruct the data packets in the proper order.

Your computer’s Initial Sequence Number at login is 24171311. You connect your computer to a computer with the IP address 210.213.23.21. This entire process takes three seconds. What is the value of the Initial Sequence Number at this time?

  • A 24171811
  • B 24171311
  • C 24619311
  • D 24171111
Explanation

The Initial Sequence Number is selected a single time when a TCP connection is established and then remains the fixed reference point for that connection's sequence-number space; per RFC 793, only the act of establishing a new connection causes a new ISN to be generated (from the clock-driven/pseudo-random generator), and mere elapsed time or an unrelated connection attempt to a different host does not alter an already-established connection's ISN. Therefore the ISN recorded at login, 24171311, is still the value three seconds later.

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