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Sakib's avatar
Sakib
Icon for Nimbostratus rankNimbostratus
May 13, 2024

How to solve "TCP retransmit timeout" & "TCP RST from remote system" issue on BIG-IP LTM?

Hi Experts,

We have an application which sends 80K+ https requests in 2 ~ 3 minutes. Client application extracts data from an API hosted behind BIG-IP . Big-IP is hosted in AWS EC2. Job was working fine for last couple of months but started failing for last three weeks. Usually, job runs for 40 minutes and extract all the data from API. No change was made on client application and on API. I captured packet in Big-IP and found that Big-IP is closing the connection with client, reasons are F5 TCP retransmit timeout and TCP RST from remote system. I applied one-connect profile with default parameter on the virtual server, now connection is not refused by Big-IP but job takes 20+ hours to extract the data from API. Applicaiton team increased backend AWS ECS instances (pool members) but no improvement. Please advise how to increase the connection on server side using one-connect profile. I haven't used it before. 

 Following is the topology: 

Client APP ----> PaloAlto Firewall ---->(Internet)----> Big-IP(AWS EC2)----(Internet)---> AWS API gateway---> AWS NLB -----> AWS ECS. 

application delivery
    • Sakib's avatar
      Sakib
      Icon for Nimbostratus rankNimbostratus
      May 13, 2024

      Thanks for the reply. I am testing the idle timeout parameter in non-prod environment. By the way issue is also happening in non-prod environment.

  • zamroni777's avatar
    zamroni777
    Icon for Nacreous rankNacreous
    May 13, 2024

    you can try disable "Acknowledge on Push" in virtual server's client (side) tcp profile,
    so bigip doesnt wait for server response for ACKnowledging client's tcp push.

    if client is not near to the aws api gw, i suggest you also check the network latency because sometime aws network routing is not optimal.
    i had experience of bad aws intercontinental latency that routing the transaction via gcp/azure resulted much higher bandwidth.

    • Sakib's avatar
      Sakib
      Icon for Nimbostratus rankNimbostratus
      May 13, 2024

      AWS region is same for Ec2 / BIg-IP , AWS API gateway , NLB and ECS. I will disable the "Acknowledge on Push" on client side TCP profile. Thank you for your reply.