looking for BIND zone constraints

Barry Margolin barmar at genuity.net
Thu Jul 5 15:53:27 UTC 2001


In article <9i1v33$l9o at pub3.rc.vix.com>,
Dykes Greg-FGD008  <Greg.Dykes at motorola.com> wrote:
>
>Need a little help in documenting the actual size constraints on a zone
>file. Is there a limit on the number of RRs in a zone file? If so, what is
>it?
>Are there any other "gotchas"? I have heard that UDP and even TCP have
>limits. Can anyone help?

I don't think there have been any zone size limits since early 4.9.x
versions.

The size limits on UDP and TCP have to do with the size of a single
response.  To hit the UDP limit you would need over 100 A records or
several dozen MX or PTR records on the same name.  To exceed the TCP limit
you would need thousands of records on the same name.  There should be
little reason to do either.

>Reason I asking these question is that I'm considering using DNS to store
>many TXT records under a host name for our system's unique application. Our
>client would do a query on the hostname and "get back" the large list of TXT
>RRs. In testing, we are seeing some fragmentation and other problems that
>prevent us from getting back the entire configured zone dataset.

UDP's limit is about 500 bytes, so if you try to store more than this for a
single hostname, it will have to switch to TCP.  Many sites block TCP
connections to their nameservers, as a misguided way to block zone
transfers, so you may encounter problems if you depend on DNS over TCP.

-- 
Barry Margolin, barmar at genuity.net
Genuity, Burlington, MA
*** DON'T SEND TECHNICAL QUESTIONS DIRECTLY TO ME, post them to newsgroups.
Please DON'T copy followups to me -- I'll assume it wasn't posted to the group.


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