Forum Discussion

rld_178240's avatar
rld_178240
Icon for Altostratus rankAltostratus
Nov 25, 2014

Slow application performance when using BIG-IP LTM VE for load balancing.

The Question   Is there some limitation on the BIG-IP F5 LTM that prevents it from being able to support a large user load and/or are there any configurations that could specifically interfere wit...
application delivery
LTM
management
performance
  • rld_178240's avatar
    rld_178240
    Feb 19, 2016

    The overall answer to this question is, yes there is a limitation... but it depends on the license type purchased. The license I had available to me had a 10 Mbps limitation on it, rendering it useless for load testing scenarios. This information in the assorted comment threads.

     

    The following references on F5 were helpful, but ultimately, I would have liked to find a SOL that explicitly calls out this limitation, as it feels somewhat masked (it may not be, when talking to account teams from F5, but unfortunately I came into this post-purchase.) It is not listed in the licensing information when running tmsh show /sys license.

     

    Thank you again to WLB for all of the help. It was WLB's guidance that helped me find the answer to this question. I am just posting the direct answer so that the thread can be closed.

     

What_Lies_Bene1's avatar
What_Lies_Bene1
Icon for Cirrostratus rankCirrostratus
Dec 03, 2014

You may also want to consider these from the v11.4 and 11.5 release notes respectively;

 

ID 409234

 

"FastL4 Virtual Servers can experience very low throughput on Virtual Edition with TCP Segmentation Offload disabled. The customer will notice a large amount of Transmit Datagram Errors for the fastl4 profile (tmsh show ltm profile fastl4)" "The customer must be running Big-IP version 11.4 Virtual Edition with at least one fastL4 virtual server configured. The customer must additionally have TCP Segmentation Offload (TSO) disabled in the TMM (sys db tm.tcpsegmentationoffload). The customer may see low throughput numbers in this configuration if their hypervisor has Large Receive Offload (LRO) enabled. This is a hypervisor configuration and is beyond our control. The customer may also see these low throughput numbers when their Virtual Edition is passing traffic to other virtual machines running on the same physical hypervisor." FastL4 virtual servers affected will have very low throughput. "The customer should enable TCP Segmentation Offload by modifying 'sys db tm.tcpsegmentationoffload'. The customer may also resolve this issue by disabling large Receive Offload (LRO) on any hypervisor they plan on running Virtual Edition."

 

ID 455361

 

Fixed improper handling of ICMP (Internet Control Message Protocol) 'Fragmentation Required' messages from routers. Bug resulted in extremely inefficient behavior by BIG-IP TCP segmentation offload if path MTU (Maximum Transmission Unit) was smaller than what TCP endpoints negotiated.