Forum Discussion

an356339_362925's avatar
an356339_362925
Icon for Nimbostratus rankNimbostratus
May 30, 2018

can someone explain persistence concept in detail with its types? not able to understand properly

not able to understand how persistence actually helps? how do we come to know which type of persistence to use in which scenario.

 

LTM
security
  • Surgeon's avatar
    Surgeon
    Ret. Employee
    May 31, 2018

    Hmm little broad information. In short - persistence allows to forward the requests from the same client to the same pool member.

     

    Let say your session requires authentication. You entered your username and pass. The current webe server holds this information. if your 2d request load balanced to the 2d pool member which has no login details you entered in the 1st pool member, you have to enter credentials again.

     

    Persistence allows you to send the 2d request to the pool member which stores login data.

     

    Every type of persistence depend on what you want to achieve and which options you have. E.g. you will not be able to use Cookie persistence for non-http traffic. In that case you will chose another e.g src ip based

     

    You can read basics here. https://support.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/ltm-profiles-reference-12-1-0/4.html

     

    If you have any questions, feel free to ask

     

  • youssef1's avatar
    youssef1
    Icon for Cumulonimbus rankCumulonimbus
    May 31, 2018

    Hi,

     

    Basicly, persistence is when we use an information from a layer below the application layer or use Application layer information to maintain a client request to a single server.

     

    Suppose you load balance several servers, the user requestion is FW to a single server because he is authenticated and working on this server. but if there is no persistence these requests would probably be spread on all the servers and he would possibly lose the work he has done on the previous server and he should potentially authenticate on each new server ...

     

    on what should we base ourselves to define a persistence:

     

    • source IP (L4, no need http profile, ...)
    • cookie (Layer 7, you need an http profile and interception if https)
    • uri (universal persistence: Layer 7, you need an http profile and interception if https)
    • SIP
    • ...

    Read this article it will help you:

     

    https://www.haproxy.com/blog/load-balancing-affinity-persistence-sticky-sessions-what-you-need-to-know/

     

    F5 article:

     

    https://support.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/ltm-profiles-reference-12-0-0/5.html

     

    regards