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0 pointsktta8y ago0 comments

Performance. Most routers also have DNS caches for the same thing. It is often recommended to use OpenDNS servers for privacy, but it is slower than your ISP's DNS or Google's.

This is especially useful when you have an application which doesn't cache DNS requests and issues a new one for every connection. Torrenting gets a big boost for example.

Privacy is just a side effect.

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mucklark8y ago· 2 in thread

I would be surprised to learn that most routers DNS implementations enforce "a long minimum global TTL". What do you define as long by the way?

EDIT: Also, "Torrenting gets a big boost for example." sounds strange, don't trackers give out IP addresses? Why would BitTorrent be DNS bound?

kttaOP8y ago

Most routers just have a DNS cache, not a global TTL, sorry about the misunderstanding.

I have it set up to be 1 day. Most websites have been setting up low TTLs like 1 hour or less because they don't want to take a chance in case of a problem, and DNS is cheap or free these days.

About your statement - 'don't trackers give out IP addresses?', what do you mean?

Often trackers are addressed by their domain (I've never actually seen a tracker without one). So each torrent has its own specific set of trackers. So all those trackers are frequently resolved and contacted for peer exchange.

mucklark8y ago

Well, trackers give out the addresses of peers. If those addresses were given out as hostnames, there'd be a lot of DNS work involved, but they don't (as far as I'm aware).

So then the DNS curb would be looking up the hostnames of the trackers, which I'd guess would be under a dozen or so hosts (I don't know, I'm just guessing) per torrent. That seems unlikely to be a hot-spot to the degree that enforcing a long cache would provide a "big boost" to overall performance.

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