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sathish_126179's avatar
sathish_126179
Icon for Nimbostratus rankNimbostratus
May 21, 2014

F5 LTM - Unable to download 5MB file

We are having an issue while trying to download a CSV file (size 5MB) via F5 LTM (version: 11.3.0). The file gets downloaded successfully when tried from backend application server. The Application server takes around 8mins to retrieve the data and downloading the file. While trying with BIG-IP LTM tries for quite some time and eventually throws "page cannot be displayed error". I guess LTM session gets timed out. Interestingly this works for smaller CSV files which are in few KBs.

 

Following are the settings related to LB:

 

  • Standard virtual server with LB virtual IP listening on port 443 (HTTPS)
  • tcp-wan-optimzed & tcp-lan-optimized applied for client & server profiles
  • No persistence profiles used
  • Automap used for Source Address Translation
  • Backend servers runs in port: 443 with "https" health monitor

Can someone throw some light on which TCP parameter needs to be fine-tuned for resolving this issues? Any help on this will be highly appreciated.

 

application delivery
design
download
LTM

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  • What_Lies_Bene1's avatar
    What_Lies_Bene1
    Icon for Cirrostratus rankCirrostratus
    May 21, 2014

    Hmmm, hard to know with so little information but certainly try and disable Delayed ACKs in the TCP profiles. Also ensure Extensions for High Performance is enabled and Nagle is not.

     

    Perhaps change Congestion Control to Scalable on the server side at least.

     

    What OS is the server running?

     

    Also, is the client side actually a WAN? Is it reliable?

     

  • HHeredia_36237's avatar
    HHeredia_36237
    Icon for Nimbostratus rankNimbostratus
    May 21, 2014

    i'd use tcpdump to sniff the conversation between client and virtual server/server to bigip to note if there's an HTTP error code or a connection reset or something else.

     

    If there'd have something wrong on f5 configuration that doesn't let you pass a 5MB file, i think it should be recorded on /var/log/ltm o messages, have you had a glance at those logs?

     

    regards, hheredia (sorry for the english :D)