title: Why do I get TCP Window Update WITHOUT ZeroWindow
body: <p>The documentation says that TCP Window Update is usually due to previous Zero Window.</p>
  
  <p>I can't find a previous zero window. What else might it be?</p>
  
  <pre><code>Transmission Control Protocol, Src Port: 5431, Dst Port: 703, Seq: 1, Ack: 38529, Len: 0
      Source Port: 5431
      Destination Port: 703
      [Stream index: 0]
      [TCP Segment Len: 0]
      Sequence number: 1    (relative sequence number)
      Acknowledgment number: 38529    (relative ack number)
      0101 .... = Header Length: 20 bytes (5)
      Flags: 0x010 (ACK)
      Window size value: 256
      [Calculated window size: 256]
      [Window size scaling factor: -1 (unknown)]
      Checksum: 0x03c0 [unverified]
      [Checksum Status: Unverified]
      Urgent pointer: 0
      [SEQ/ACK analysis]
          [TCP Analysis Flags]
              [Expert Info (Chat/Sequence): TCP window update]
  </code></pre>