2 Comments

  1. I understand the concept of SRV records, but I have a question. Once a client detects that the highest priority address is unavailable, I know that it switches to using the backup address. But, what does it do to ensure that it doesn’t retry the primary address next time it has a request to send? Does it flush the primary details from its cache, hence being left with the secondary only? I assume that it then relies on the TTL to flush its cache, which then restores the primary address to the cache, allowing it to be tried again. If it is still failing it will be removed from the cache again. Eventually the primary will be restored and the cache restoration following its recovery will result in it being used again.

    Is this a correct understanding?

    Thanks in advance for your feedback.

  2. Most browsers and servers have another fail over mechanism. A server publishes many ips for one address. Smart browsers choose one ip randomly and keep trying until it connects to the good one. That’s how very large site like cnn handle fail over automatically; there was no need for change the A record just when you have a crash.

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