North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: Content Delivery Networks
"Chris L. Morrow" <[email protected]> writes: > that sets a lower-bar on TTL in the nscd cache - > > (from the manpage for nscd.con) > > positive-time-to-live cachename value > Sets the time-to-live for positive entries (successful > queries) in the specified cache. value is in integer > seconds. Larger values increase cache hit rates and > reduce mean response times, but increase problems with > cache coherence. Note that sites that push (update) > NIS maps nightly can set the value to be the > equivalent of 12 hours or more with very good perfor- > mance implications. > > > This is still a client issue as, hopefully, the cache-resolvers don't > funnel their business through nscd save when applications on them need > lookups... (things like ping/telnet/traceroute/blah) nscd may represent a problem if the application in question is a http-proxy without it's own resolver. There's also a number of more-or-less broken http-proxies doing their own resolver caching regardless of actual TTL. Such applications represent a problem wrt any DNS-based load balancing, including CDNs, since they can serve a large number of end-users, redirecting them to the "wrong" address long after the TTL should have expired. Bjørn
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