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Dan_140818's avatar
Dan_140818
Icon for Nimbostratus rankNimbostratus
Jan 13, 2014

GTM Topology Load Balance

Scenario: Two data centers exist. One for the west coast, the other for the east coast. The load balancing method is based on topology. Domain name = svc.company.com West-coast DC IP = 10.0.0.1 East-coast DC IP = 10.0.0.2 The topology load balancing method is not very precise, because it is based on the geo-location of the user's DNS server, not the user's IP.

 

Suppose that a user from the west-coast is directed to the east-coast data center: Svc.company.com resolves to 10.0.0.1 How can the user be redirected to the west-coast, so that in the end svc.company.com resolves to 10.0.0.2? Thanks

 

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  • Jason_40733's avatar
    Jason_40733
    Icon for Cirrocumulus rankCirrocumulus
    Jan 13, 2014

    If I understand correctly, you want someone on the west-coast who is using an east-coast DNS resolver to be directed to the west-coast DC IP?

     

  • Dan_140818's avatar
    Dan_140818
    Icon for Nimbostratus rankNimbostratus
    Jan 13, 2014

    Yes, we have 2 GMTs (synced) one east coast and one west coast. We would like to ensure the west coast user if "misdirected" to east coast destination would be directed back to west coast destination. (Same would apply for an east coast user that was "misdirected" to the west coast). Thanks.

     

    • Jason_40733's avatar
      Jason_40733
      Icon for Cirrocumulus rankCirrocumulus
      Jan 13, 2014
      I follow. In that scenario, the GTM has already done its job and sent back the requested IP. The redirect at this point would need to come from the client service in your DC when the client connects. If you have an F5 LTM... "there's an i-Rule for that". Other vendors I can't speak to. Check this link on state-by-state iRule. Written by the great Rahm: https://devcentral.f5.com/s/articles/new-geolocation-capabilities-in-v101 Hope that gives you what you need.
  • IheartF5_45022's avatar
    IheartF5_45022
    Icon for Nacreous rankNacreous
    Jan 13, 2014

    GSLB technology alone, when used for the attempted assignation of the nearest service to a given user, is inherently flawed (as you say above), as it relies on the source IP of the users DNS server, not their IP. In addition, the IP of a users DNS server may change during a session for (multiple reasons) meaning it's not terribly useful for site persistence purposes either.

     

    • Having location-based domains as in Jasons link above is one way around it, but the business may have reasons (not necessarily good ones) for not wanting to pollute their carefully chosen domain names for performance.

       

    • Using anycast for the DC endpoints is another possibility to consider for non-mobile users.

       

    • If those options are not palatable just accept that some users will not end up at the most optimal datacentre for them.

       

    Whichever way - the GTM still provides an invaluable service by determining the state (UP/DOWN) of a DC before providing a response and if you are using for site persistence also, will give the majority of users persistence to a site, but you will have to work out a way to cater for the chunk of users who float sites during a session.

     

    Just my 2c worth.....