This is our old Q&A Site. Please post any new questions and answers at ask.wireshark.org.

Investigating some sending latency in a packet capture shows a continual pattern of packet sends sometimes waiting for an incoming Ack:

-> Timely outgoing packet
-> Timely outgoing packet
.. (waiting)
<- Ack
-> Delayed outgoing packet

Strace shows the write calls to the kernal are all timely. TCP no delay is enabled. The two main obvious candidates for the kernel awaiting an ack before sending a buffered packet would be congestion window or receiver window. But there is no packet loss at all, so presumably the cwnd will be sufficiently high, and the window sizes in the incoming acks show no problems with rwnd values. Are there any other reasons that could delay a packet being sent before an ack is received?

asked 18 Jun '15, 00:33

glyn_walters's gravatar image

glyn_walters
6112
accept rate: 0%

Be the first one to answer this question!
toggle preview

Follow this question

By Email:

Once you sign in you will be able to subscribe for any updates here

By RSS:

Answers

Answers and Comments

Markdown Basics

  • *italic* or _italic_
  • **bold** or __bold__
  • link:[text](http://url.com/ "title")
  • image?![alt text](/path/img.jpg "title")
  • numbered list: 1. Foo 2. Bar
  • to add a line break simply add two spaces to where you would like the new line to be.
  • basic HTML tags are also supported

Question tags:

×17

question asked: 18 Jun '15, 00:33

question was seen: 857 times

last updated: 18 Jun '15, 00:33

p​o​w​e​r​e​d by O​S​Q​A