Subject: [Enum] How long will it take to update a NAPTR record?

From: "bill" <[email-masked]>
Date: Tue, 19 Mar 2002 06:54:08 -0800

Folks:

There is machanism which make DNS to update a record in about several 
hours. The time to be used is determined by the TTL, refresh time, 
caching and etc. Have anybody consider the following question:

When an ENUM subscriber want to change his NAPTR record in real-time, 
i.e. two mininute, like call transfer function provide by the telcom 
system, how to reflect changes into the DNS servers?

There are many cases that need the ENUM DNS response in real-time to 
satisfy the user's demand.

Any comments?

Bill

CNNIC
[email-masked]

2002/03/19 

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From: Patrik Fältström <[email-masked]>
Date: Tue, 19 Mar 2002 09:05:17 -0600

> system, how to reflect changes into the DNS servers?

The mechanism that can be used is called DNS Dynamic Update. Since an
interoperability test which was run in January this year, we know secure
dynamic update is possible with both the TKEY and SIG(0) mechanisms. It is
used at the IETF meeting here in Minneapolis for IPv4 addresses, and I for
example is using it myself (you can have a look at the IP-address for
zx81.paf.se which is the address my laptop have, or rather, last address it
had).

> satisfy the user's demand.

The update with dynamic update is instanatous, but, one still need to have
a TTL on the record itself. It is recommended that the TTL is around 60
seconds, and not shorter. That means that someone which queried for the
record 1 second before you changed the record will have the wrong data for
another 59 seconds.

This is the reason why I in 2916 wrote that DNS can not be used for "real
time updates".

It can be used if you with "real time" accept around 30 seconds of
instability for _that_ DNS record.

If you have suggested wording for 2916bis which clearifies this, please
send the information in my direction.

      paf

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From: Jim Reid <[email-masked]>
Date: Tue, 19 Mar 2002 07:40:27 -0800

>>>>> "bill" == bill  <[email-masked]> writes:

    bill> Folks: There is machanism which make DNS to update a record
    bill> in about several hours. The time to be used is determined by
    bill> the TTL, refresh time, caching and etc. 

This is straightforward on a UNIX system. Tools like at or cron can be
used to arrange for things to be done at a specific time. For instance
they could run scripts that call nsupdate to make a Dynamic Update
request. The trick will be to ensure that the update gets propagated
quickly to all the zone's name servers and that any stale data for the
name that gets updated doesn't get cached for too long by other name
servers.