Date: Wed, 26 Jan 2000 11:14:56 -0800 From: "Kevin Oberman" <oberman@es.net> To: keith@mail.telestream.com Cc: freebsd-questions@FreeBSD.ORG Subject: Re: Off topic Message-ID: <200001261914.LAA30006@ptavv.es.net> In-Reply-To: Your message of "Wed, 26 Jan 2000 10:47:32 PST." <Pine.LNX.4.10.10001261043450.19619-100000@mail.telestream.com>
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This would be more appropriate to a BIND news group, but... The number is the TTL (Time To Live) for the record. The record has been cached by the server you queried with a defined TTL which starts counting down immediately. This is set up in the BIND datafile either in the SOA record (BIND versions before 8.2) and with a $TTL declaration (V8.2 and higher). Good BIND admins set large TTLs for things which rarely change and smaller TTL for less stable items. Once a system caches the data, the TTL starts decrementing. When it reaches zero, it will no longer be set out in a response and the authoritative source will be queried. This new data is then cached for the TTL specified. Every record comes with a TTL and that TTL is defined by the nameserver which is authoritative for that record. So the A RR for b.ns.verio.net will remain in the cache for an additional 1 day, 7 hours, 6 minutes and 2 seconds after the query you made. somedomain.com will remain the same for 55 minutes and 3 seconds. This means that all queries for a given record will be resolved the same way until TTL expires regardless of what the authoritative data on the master server says. The only exception to this is when the DNS on the server you are querying is restarted since the cache is in memory and the server always starts with an empty cache. R. Kevin Oberman, Network Engineer Energy Sciences Network (ESnet) Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab) E-mail: oberman@es.net Phone: +1 510 486-8634 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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