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client latency


Hi, I came across a trace where my monitoring point is close to the client. I am looking at the response time of the basic TCP handshake SYN- SYN/ACK ACK

My SYN/ACK from the server takes reasonable time but my ACK from the client is sporadic and taking longer time.

what could be the potential reason the client is taking longer time to ACK.

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asked 06 Aug '13, 16:12

pappu's gravatar image

accept rate: 0%

2 Answers:


I interpret the issue as: Mostly the ack from the client comes in within sub-ms but occasionally it takes x ms. There are two reasons why this could happen:

  1. The client's TCP didn't see the syn-ack in time
  2. The client's TCP didn't process the packet in time

My first guess would be the client is running in a virtualized environment and doesn't get dispatched in time. Do you see higher delays also later in the conversation?

answered 06 Aug '13, 20:49

mrEEde2's gravatar image

accept rate: 20%

thank you for your reply.... clients are not running in virtual environment. It is a regular PC at a store which has T1 connectivity back to the datacenter. I have a feeling the PC is late in processing ...probably old PC....some application like java on the PC is taking time to process the data received.

(29 Sep '13, 18:41) pappu


what could be the potential reason the client is taking longer time to ACK.

a large network load on the client. If the internal transmit buffers are filled up, it will take longer to get the ACK out on the line.

There is probably also a duplex problem on the client. If the client works in half duplex mode and receives/sends a lot of traffic, this could also cause delays in sending the ACKs, due to collisions and other network related problems.


answered 08 Aug '13, 02:52

Kurt%20Knochner's gravatar image

Kurt Knochner ♦
accept rate: 15%