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my assumption was that the DNS load balancing is the way for the top level load balancing:

In older posts I see that google returned multiple A records. At least in the theory, it should provide not only load balancing, but also a fallback for clients, if first/some of IPs aren't working. But now I see that google (and facebook) returns only one record of type A. It seems still returning different IPs, but what is the reason behind? Is there any other way to provide possibly better load balancing and/or reliability?

EDIT: Found this answer about TCP anycast. I'm not comfortable enough with networking, but it seems like a valid way to handle the challenge.

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  • I think they have a huge first cluster that redirects to the next server that should do the way you tell
    – djdomi
    Oct 10, 2021 at 13:45
  • @djdomi what do you mean by huge cluster? How it's load balanced? Oct 10, 2021 at 15:51
  • "At least in the theory, it should provide not only load balancing, but also a fallback for clients, if first/some of IPs aren't working. " If clients know how to use multiple IP addresses... which is certainly not guaranteed. Oct 10, 2021 at 16:58

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No.

There are several ways of implementing load-balancing. DNS RR can be one of them, but it's huge fallback is that when some of your RR endpoints aren't healthy - for instance they are up and receiving connections, but cannot forward requests, or some of their backends aren't answering in time, or down - the client will get an error.

If it has already a happy eyeballs implementation, which can help the modern browsers to bypass failing RR endpoint nodes, which isn't alwats the case - espacially when the client isn't a web browser.

Furthermore, you cannot make huge assumptions from observing top 0.01% of each unicord infrastructure facing the public world.

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  • Thanks for your reply. Do you mean rfc6555? "you cannot make huge assumptions from observing top 0.01% of each unicord" - I'm interested in concepts and possibilities behind that. Oct 10, 2021 at 15:55

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