New Resource Limits


max-cache-ttl is a new option that sets the maximum TTL for caching of ordinary (positive) records. This overrides whatever might be set in the SOA record for the record, if it's higher than this value. This helps limit the size of the cache to some degree, but it also enables you to override excessively high TTL values. The default value is one week.

recursive-clients, defaulting to 1000, limits how many recursive queries can be in progress at any one time. If you have several clients, this might have to be increased. In fact, it has already proven to be too low, so the default might be much higher by the time you read this.

tcp-clients, defaulting to 100, limits how many simultaneous client connections over TCP named can keep. TCP connections eat file handles and possibly free i-nodes in the OS tables, possibly causing starvation on the system. 100 is a very low value, but some older UNIX versions need this value set well below 64, so don't laugh. Most modern UNIX versions will work even if the number of simultaneous TCP connections in BIND passes 255, but check your OS documentation.

max-cache-size is, alas, not implemented in BIND 9.0.0. It will, when implemented, enable you to limit the memory consumption of the cache in your server. BIND 8 can control the total size of its data structures with the datasize option, but when the size is passed, BIND dies. max-cache-size, then, is a much better idea. Of course, the amount of memory used by BIND is also determined by other dynamic things, but mainly by the number and size of the zones for which the server is authoritative.



The Concise Guide to DNS and BIND
The Concise Guide to DNS and BIND
ISBN: 0789722739
EAN: 2147483647
Year: 1999
Pages: 183

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