Search Again: Re: Cache From: Chris Buxton Date: Monday, May 3, 1999 Time: 9:16:00 am >Does the cache in QDNS flush over a certain time period or does this need >to be done manually? > >or > >Should the cache be flushed? It seems there are so many changes to IP >addresses/Domain Names that some of the cached info can become outdated in >a very short time. I know I have made changes and there have been certain >ISP's that took 2 weeks before the DNS info changed on their servers. Theoretically, data is flushed when it becomes stale. Every DNS record has a time-stamp when it is sent out by the authoritative server, called the time to live (or TTL). For those records whose TTL field is blank, it is supplied by the SOA record's default TTL (aka the "minimum"). (The SOA record is the domain's information dialog in QuickDNS Pro Admin.) When a non-authoritative server gives out the record, it includes a TTL that has been shrunk by the amount of time since the record was retrieved from an authoritative server. If your TTL is set to two weeks (in seconds - far longer than it probably should be), it would take an ISP's server up to 2 weeks to notice any changes. Your default TTL should probably be around 8 hours. Another reason is more likely: some DNS servers ignore the TTL and keep using records they get from other servers long after the data become stale. This is known as bad programming. Furthermore, some servers are written only a little badly, and will pass on the original TTL of the record, rather than modifying it for age. For this reason, you can reasonably expect that nearly all servers will notice your changes after twice the TTL (in seconds) has passed. I hope this clears things up for you. ________________________________ Chris Buxton Internet and Database Consultant

Messages In This Thread: Cache by Tony on May 2, 1999 at 11:30:00 pm Re: Cache by Chris Buxton on May 3, 1999 at 9:16:00 am