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f5n00bie_77440's avatar
f5n00bie_77440
Icon for Nimbostratus rankNimbostratus
Nov 24, 2010

Link Controller - outbound load balancing

Hi,

 

 

I am new to F5s and implementing link controllers and trying to design a solution to meet the customers requirement of outbound link selection based on best performance, for a specific URL.

 

 

 

The closest article I could find on link selection based on performance was here: http://support.f5.com/kb/en-us/prod...tml998646

 

 

 

Basically this article talks mainly about inbound load balancing and virtual server selection based on link performance characteristics. This selection of VS would ultimately influence the ISP link chosen to carry the traffic.

 

 

 

Is it possible to dynamically perform outbound traffic ISP link selection based on the best performance characteristics to a specific URL with a link controller?

 

 

 

Thanks for reading

 

config
design

3 Replies

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  • Chris_Miller's avatar
    Chris_Miller
    Icon for Altostratus rankAltostratus
    Nov 24, 2010
    You could certainly use tcp::rtt to look at the round trip time to the destination through 2 different pool members. The real question is, how often do you care about performance? If Link B is 5 ms faster than Link A, do you want to use Link B every single time even though the client would never notice?
  • f5n00bie_77440's avatar
    f5n00bie_77440
    Icon for Nimbostratus rankNimbostratus
    Nov 24, 2010
    Thanks and agreed, I find the requirement quite feckless. However, if packetloss could be monitored, that may provide some tangible benefit.

     

     

    Another concept I need to understand is how the default-gateway route is chosen by the link controller for outbound traffic by default.

     

     

    As far as I can see default-gateway load balancing is performed by round robin by default, even when dynamic ratio is applied (unless you change the ratios from 1:1) is this correct?

     

     

  • Chris_Miller's avatar
    Chris_Miller
    Icon for Altostratus rankAltostratus
    Nov 29, 2010
    f5noobie - I assume you've got a pool which contains your routers? Depending on the load balancing algorithm for that pool, you may or may not use round robin. Least connections for instance would use the link with, well, the least connections. :-P