Ethereal-users: [Ethereal-users] Are unchanging sequence numbers normal in TCP Acks?

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From: David Wuertele <dave-gnus@xxxxxxxxx>
Date: Tue, 15 Jun 2004 15:59:53 -0700
I'm using ethereal to analyze the http download of a large file, and I
notice that once the client finishes its request, and starts sucking
down packets, it sends nothing but Ack packets with the exact same
sequence number.  Here's a snippet:

9593  57.907463 169.254.242.55 -> 169.254.15.185 TCP 12956 > http [ACK] Seq=19 Ack=6374361 Win=6732 Len=0
9594  57.908400 169.254.242.55 -> 169.254.15.185 TCP 12956 > http [ACK] Seq=19 Ack=6375821 Win=6732 Len=0
9595  57.914819 169.254.15.185 -> 169.254.242.55 HTTP Continuation
9596  57.915472 169.254.242.55 -> 169.254.15.185 TCP 12956 > http [ACK] Seq=19 Ack=6377281 Win=6732 Len=0
9597  57.917170 169.254.15.185 -> 169.254.242.55 HTTP Continuation
9598  57.919047 169.254.15.185 -> 169.254.242.55 HTTP Continuation
9599  57.919980 169.254.242.55 -> 169.254.15.185 TCP 12956 > http [ACK] Seq=19 Ack=6378741 Win=6732 Len=0
9600  57.925334 169.254.242.55 -> 169.254.15.185 TCP 12956 > http [ACK] Seq=19 Ack=6380201 Win=6732 Len=0
9601  57.926289 169.254.242.55 -> 169.254.15.185 TCP 12956 > http [ACK] Seq=19 Ack=6381661 Win=6732 Len=0
9602  57.927124 169.254.242.55 -> 169.254.15.185 TCP [TCP Dup ACK 9601#1] 12956 > http [ACK] Seq=19 Ack=6381661 Win=6732 Len=0
9603  57.928182 169.254.242.55 -> 169.254.15.185 TCP 12956 > http [ACK] Seq=19 Ack=6383121 Win=6732 Len=0
9604  57.934696 169.254.15.185 -> 169.254.242.55 HTTP Continuation

Notice that everything from the client (169.254.242.55) has the same
Sequence Number.  Is that normal when the packet has nothing in it but
a TCP Ack?

Thanks,
Dave