<html><head></head><body><div class="ydp861edcb0yahoo-style-wrap" style=""><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;">Hi all,</div><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;"><br></div><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;">Wanted to congratulate you on great work with unbound !</div><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;"><br></div><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;">My use case of unbound is on ships using satellite uplinks, so in other words high-latency and high-bandwidth... relatively speaking, but surely enough bandwidth for DNS queries.</div><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;">So idea would be to cache and then preemptively re-cache DNS queries as much as possible so to speed up Internet access for users.<br></div><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;"><br></div><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;">This could cut up to 500-800 ms from every DNS query and remove lag on DNS side. This, together with WAN TCP optimization (SYN) would make satellite uplink not so laggy for users onboard.</div><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;"><br></div><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;">So I notice most of the DNS entries rarely change and local unbound onboard could surely cache lots of entries considering memory and CPU are available nowadays.</div><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;"><br></div><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;">Thus instead of expiring cached entries after TTL I would like to keep refreshing them regularly and keep them available for some pre-defined time </div><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;">(eg. 2-3 weeks configurable) due to cruise length. I believe this proactive approach with cache & refresh would be more appropriate for such environment.<br></div><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;"><br></div><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;">Checking out for options in Unbound I have identified couple of mechanisms to enable this but all seem to lack some features.</div><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;"><br></div><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;">Prefetch is great feature but seems somewhat limited for entries to be refreshed during last 10% of TTL and only if user resolve entry during that last 10% of TTL time.</div><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;">Furthermore that 10% seems not configurable in config.<br></div><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;">I know setting it like this increases cache hit ratio for often used entries (ones that also get hit during last 10%) but is not flexible enough.<br></div><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;"><br></div><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;">I am trying to cache much beyond that time frame (2-3 weeks - parameter 1) and cannot always guarantee users will be resolving within last 10% of TTL (eg. during night) <br>so I would like to set automated refresh to do refresh on 90% TTL, if DNS entry was asked for more or equal to 0 ... n times after being cached (parameter 2).</div><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;"><br></div><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;">Of course all up to maximum number of cached entries which would be set appropriately.</div><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;"><br></div><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;">This would allow for preemptive caching based on number of times entry is queried during TTL and overall length of time to keep such entries in cache.</div><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;">So in other words we would trade-off some bandwidth used in order to reduce DNS latency.</div><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;"><br></div><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;"><span>Serve-expired is another great feature, but what I am proposing above would work similarly and wouldn't break DNS in case entries are changed, </span></div><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;"><span>though with some bandwidth trade-off for refreshes.</span><br></div><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;"><span><br></span></div><div style="">cache-min-ttl would definitely break certain resolutions, but I would use it with 30 - 60 min TTL which is sensible trade off </div><div style="">so refresh doesn't happen too often and any changes are still picked up with regular refreshes.</div><div style=""><br></div><div style="">Is there anything else that I could use out of the box? What other existing parameters would help towards this caching goal?<br></div><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;"><br></div><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;">Thanks,</div><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;">Tiho</div><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;"><br></div></div></body></html>