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Hannes_Rapp's avatar
Hannes_Rapp
Icon for Nimbostratus rankNimbostratus
Aug 11, 2015

TCP Request Queueing

Hi,

I'm facing a problem with TCP request queue feature.

Scenario:

1 member in Pool

Connection limit 2 (set on Pool Member)

TCP Request Queue Enabled

TCP Request Queue Depth 8

Expecting the following:

As I initiate 10 concurrent connections, all connections will be handled successfully, 2 at a time

  • 2 Connections are accepted instantly (limit not reached)

  • 8 Connections are forwarded to queue (limit is reached)

  • any excess while the queue is full will be reset (F5 sends TCP/RST in response)

Actual scenario:

Only 4 connections are handled successfully

  • 2 Connections are accepted instantly (limit not reached)

  • 2 Connections are forwarded to queue (limit is reached)

  • and 6 connections fail as they receive TCP/RST from F5 in response.

Question

How can I force all the excess connections to queue? The configuration utility accepts any number to be set as 
queue depth
, but in reality it only appears to accept as many connections in queue as the limit on a single pool member.
application delivery
LTM

1 Reply

  • svs's avatar
    svs
    Icon for Cirrostratus rankCirrostratus
    Mar 23, 2017

    Hi,

     

    I know, that this is a quite old question, but while looking for informations on TCP request queue, I stumbled over this question.

     

    It's a well documented fact, that the TCP request queue may not be configured higher than the cumulative total amount of connection limits defined for every pool member. So in you case, 2 connections is the correct limit. When you configure i.e. 3 pool member and every pool member allows a limit of 10 connections, the max. number of connections for the request queue will be 30.

     

    You can find this information in the manual: https://support.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/ltm-implementations-11-1-0/27.html

     

    The maximum number of connection requests within the queue, which equates to the maximum number of connections within the pool, pool member, or node. Specifically, the maximum number of connection requests within the queue cannot exceed the cumulative total number of connections for each pool member or node. Any connection requests that exceed the capacity of the request queue are dropped.

     

    Greets, svs