[OpenWrt-Devel] ddns-scripts "sleep 10" before updating?

Catalin Patulea cat at vv.carleton.ca
Thu Jan 15 00:17:41 EST 2015

On Tue, Jan 13, 2015 at 8:56 AM, Christian Schoenebeck
<christian.schoenebeck at gmail.com> wrote:
> from my point of view 10 seconds to wait before sending an update to the ddns provider is not a big deal because it takes up to 5 minutes until "nslookup [yourhost]" gives you back a static answer after a change.
> So Google's mameserver need up to 5 Minutes to sync themselves.
How did you conclude about the 5 minutes? Technically caching DNS
servers should respect the TTL of the original record. RFC 1035 even
allows zero TTL to prevent caching. I agree that some servers may
actually impose a minimum TTL, but ddns-scripts should not make any
assumptions about this.

In my case, I have DDNS records which are rarely accessed (are not
likely to be cached by intermediate DNS servers). When a client makes
a DNS request for my DDNS name, it will be forwarded the entire way to
the authoritative DNS server. So the openwrt update latency dominates
the delay, not TTL expiration, so it's useful for me to update ASAP
after the interfaces gets an address.

Are you still planning on running some tests on your side?
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