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avnishvyas_1974's avatar
avnishvyas_1974
Icon for Nimbostratus rankNimbostratus
Aug 11, 2016

fastl4 Protocol Profile turning on

Hello People

 

was wondering if i can get some guidance for a solution. So we have a IP forwarding VIP used specifically for FTP traffic. The issue that is being experienced is that the client is trying to send over 100 files the files start to transfer but once it reaches up to 24 files the transfer just pauses and eventually stops. The client will restart the session but is unable to connect for about an hour then will try again and the same thing starts happening. I placed a TCPDUMP on the F5 and could see the FTP traffic passing, however in closer inspection i could see repeat SYN-ACKS being passed through. These are from the destination client and it seems like there is some buffering occuring somewhere but im unable to determine where. I have had the Speed/Duplex checked on the switch and server and both are set to 1000/Full Duplex and there are no obvious errors on the switchport,

 

I had a look around on the F5 website and found sol7595: Overview of IP forwarding virtual servers so what im attempting to do is set up another FastL4 Protocol Profile and turn on the feature "Proxy Maximum Segment" to see if thise resolves the issue. Sounds very familiar to these symptoms

 

"For our situation, one thing we noticed was that the MSS is negotiated between the LTM and client at (something like) 1380 and was negotiated to 1480 between the LTM and web server. With large files, this caused the LTM to have to fragment each packet and significantly slowed down the overall download speed."

 

Does anyone else have any similar situations with enabling "Proxy Maximum Segment" ??

 

ltm virtual /Common/preprod.ftp.com { description " pre_prod FTP virtual Server"

 

destination /Common/0.0.0.0:0 ip-protocol tcp mask 255.255.255.255 pool /Common/Pool_FTPS profiles { /Common/fastl4 { } } source 0.0.0.0/0 source-address-translation { type automap } translate-address enabled translate-port disabled

 

cloud
LTM

5 Replies

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  • jgranieri's avatar
    jgranieri
    Icon for Nimbostratus rankNimbostratus
    Aug 11, 2016

    if you using IP Forwarding VS then the F5 is not proyxing the connection. I recommend trying standard VS and setup a FTP profile and attach to the VS. Have you tried that combination? You might need to tweak some of the TCP profile settings.

     

  • boneyard's avatar
    boneyard
    Icon for MVP rankMVP
    Aug 13, 2016

    in which profile are you planning to enable "Proxy Maximum Segment"?

     

    if you got support then contacting them might be wise, tweaking things like this is usually best while being managed by them.

     

  • avnishvyas_1974's avatar
    avnishvyas_1974
    Icon for Nimbostratus rankNimbostratus
    Aug 19, 2016

    Hi Guys update to the issue. Unfortunately the customer faslL4 protocol profile has not worked as expected. infact it has made no difference at all to the issue. The client does a bulk file tranfer using LFTP and it seems to freeeze once it reached 24 files. The client cannot reconnect until after about an hour or so. When the client adds a 2 sec delay between files all the files are copied across without any issues. The issue seems to occur when they copy ALL files in one hit? Im running out of ideas here and not sure what else the F5 can do to assist the situation and im un a battle with the application team who blame the network. and the network team (myself) blame the app or the server either way we have had a week of this with very little progress albeit the workaround in place

     

    • jgranieri_42214's avatar
      jgranieri_42214
      Icon for Nimbostratus rankNimbostratus
      Aug 19, 2016

      Can you gather a packet capture on the F5 and also on the FTP server while the transfer occures. Usally a PCAP will give you some indication of where the problem lies.

       

    • boneyard's avatar
      boneyard
      Icon for MVP rankMVP
      Aug 21, 2016

      i would point again to support, you might not be able to do remote session but involving them seems like the logical choice if nothing else turns up here and you clearly want a solution.

       

      as for the issue, when you send multiple files in one batch, are those send at the same time or after each other?