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Latency on Citrix sessions

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Hi, we have some latency problems on our Citrix XenDesktop 6.5 sessions (regular 5sec freeze) Here is a sample of captured packets :

[TCP Dup ACK 4#1] 59193 ; citriximaclient [ACK] Seq=106 Ack=4294965385 Win=610 Len=0 SLE=4294966845 SRE=1461

[TCP Dup ACK 4#2] 59193 ; citriximaclient [ACK] Seq=106 Ack=4294965385 Win=610 Len=0 SLE=4294966845 SRE=2914


[TCP Dup ACK 4#3] 59193 ; citriximaclient [ACK] Seq=106 Ack=4294965385 Win=610 Len=0 SLE=4294966845 SRE=4366


[TCP Dup ACK 4#4] 59193 ; citriximaclient [ACK] Seq=106 Ack=4294965385 Win=610 Len=0 SLE=4294966845 SRE=5821


[TCP Dup ACK 4#5] 59193 ; citriximaclient [ACK] Seq=106 Ack=4294965385 Win=610 Len=0 SLE=4294966845 SRE=7279 [TCP Dup ACK 4#6] 59193 ; citriximaclient [ACK] Seq=106 Ack=4294965385 Win=610 Len=0 SLE=4294966845 SRE=8737


….


[TCP Dup ACK 4#43] 59193 ; citriximaclient [ACK] Seq=106 Ack=4294965385 Win=610 Len=0 SLE=4294966845 SRE=57289


[TCP Dup ACK 4#44] 59193 ; citriximaclient [ACK] Seq=106 Ack=4294965385 Win=610 Len=0 SLE=4294966845 SRE=57788


[TCP Fast Retransmission] citriximaclient ; 59193 [ACK] Seq=4294965385 Ack=106 Win=511 Len=1460

We can see 44 DUP ACK sent from the Citrix client to the server during 200 ms.

Is this the reason of our latency ?

How can we reduce that ?

asked 29 Jul ‘14, 01:41

yoyo35's gravatar image

yoyo35
11●1●1●2
accept rate: 0%

Is this the reason of our latency ?

maybe, because the latency problem certainly has a reason. ;-))

How can we reduce that ?

I don’t know, because doing packet analysis, based on a heavily reduced text representation of the capture file is:

  • near to impossible
  • furthermore, time consuming and thus not really motivating for those you are asking for help
  • and … boring

;-))

So, if you want an answer that is at least close to what is (possibly) happening, you should post the capture file somewhere (google drive, dropbox, cloudshark.org). If you have concerns about privacy issues, you can anonymize the file with TraceWrangler, a tool of our member @Jasper.

(03 Aug ‘14, 10:49) Kurt Knochner ♦

One Answer:

0

Hi,

I don't think the Dup ACKs are causing the 5 second freeze if that's what you are asking. The 5 second freezes and Dup ACKs could have the same cause. To get a delay of 5 seconds due to a transport issue you would see either a TCP window issue or several TCP Retransmissions with significant delays between each.

I notice the client seems to be advertising a Window of 610. I guess we've missed the session start and so Wireshark doesn't have scaling info, hence the strange value. Anyway the server must think the window is bigger coz it sends 1,460 bytes.

Where was the trace data captured?

answered 04 Aug '14, 15:31

PaulOfford's gravatar image

PaulOfford
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accept rate: 11%