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Stuart_Page_131's avatar
Stuart_Page_131
Icon for Nimbostratus rankNimbostratus
Aug 21, 2013

Discrepancy: Current Virtual Server Connections

I've noticed a discrepancy between the way the F5 cluster and Exchange measures CAS connections. When checking the number of current connections in the F5 virtual server stats for Exchange OWA (HTTP/HTTPS), I was very surprised to see that the number of connections was far higher (as much as 5 times higher!) than the number being reported by Exchange.

 

I was wondering if this is due to a difference in how "connections" are counted. If so, how are connections counted by the F5 virtual server stats?

 

application delivery
cas
exchange 2010
management
microsoft
performance

11 Replies

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  • mikeshimkus_111's avatar
    mikeshimkus_111
    Historic F5 Account
    Aug 21, 2013

    Hi Stuart, are you using OneConnect on the VIP? If so, BIG-IP will reuse existing server-side connections. You won't see a 1-to-1 ratio of client/server connections. You can see OneConnect profile reuse stats in the GUI or by running "show ltm profile one-connect "

     

    This is on top of the total number of connections to the VIP being divided (hopefully) evenly among your pool members.

     

    Mike

     

    • Stuart_Page_131's avatar
      Stuart_Page_131
      Icon for Nimbostratus rankNimbostratus
      Aug 21, 2013
      As far as I can tell, I'm not using OneConnect. Good to know though. Thanks!
  • adiezma_1656's avatar
    adiezma_1656
    Icon for Nimbostratus rankNimbostratus
    Aug 21, 2013

    Hi,

     

    If you have a proxy in the middle of the connection, you maybe exists duplicated in the connections.

     

    A. Diezma

     

  • eey0re's avatar
    eey0re
    Icon for Cirrostratus rankCirrostratus
    Aug 21, 2013

    Are you sure you're not comparing OWA user sessions to TCP connections? There will typically be up to 8 times as many TCP connections as there are user sessions (due to the 8-connections-per-hostname limit in most browsers). 5 sounds like an expected multiple.

     

    Otherwise I'd say wherever you're monitoring connections in Exchange must be counting things differently - perhaps not counting Keep-alive (but idle) TCP connections.

     

  • nitass's avatar
    nitass
    Icon for Employee rankEmployee
    Aug 22, 2013

    I was wondering if this is due to a difference in how "connections" are counted. If so, how are connections counted by the F5 virtual server stats?

     

    i understand F5 connection is tcp connection which is in F5 connection table. is it same as in Exchange?

     

    • nitass's avatar
      nitass
      Icon for Employee rankEmployee
      Aug 22, 2013
      i do not think number of tcp connections is going to be equal to number of user sessions.
  • nitass_89166's avatar
    nitass_89166
    Icon for Noctilucent rankNoctilucent
    Aug 22, 2013

    I was wondering if this is due to a difference in how "connections" are counted. If so, how are connections counted by the F5 virtual server stats?

     

    i understand F5 connection is tcp connection which is in F5 connection table. is it same as in Exchange?

     

    • nitass_89166's avatar
      nitass_89166
      Icon for Noctilucent rankNoctilucent
      Aug 22, 2013
      i do not think number of tcp connections is going to be equal to number of user sessions.