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Spirent TestCenter: What is the ALP HTTP and RawTCP behavior with and without Delay Ack?

Environment/Versions
  • Configuration window ‘all profiles  > RAW TCP Servers’  there is an attribute for ‘Enabled Delayed ACK’ that may be selected for each profile.
  • If disabled, does this mean there is an ACK sent for each attempted connection and the ACK is not delayed?  
  • How long is the default delay?  
  • If I select this feature how much delay is added to the ACK reply?
Answer
  • The Delayed ACK feature is not working and the behavior is the same whether enabled or not.
  • Behavior:
    • This is a BSD-based stack with no QUICKACK, the tcp ack delay is 100ms.
    • This is the delay that it uses before acking an incoming packet if it has nothing to send in response. If it does have something to send it will combine the ack and the new data.
  • I think in ALP normally this is a good thing. There are other rules on when to send an ACK if a multiple of packets come in and that's usually the case in ALP so I don't think the delay or lack of delay has an impact in normal ALP testing.
 
  • A defect was originally opened but it was declined. Behavior is as indicated above. No changes intended.

Product : Spirent TestCenter,Raw TCP,HTTP,ALP