truncated responses vs. minimal-responses?

Matus UHLAR - fantomas uhlar at
Wed Nov 28 15:19:07 UTC 2012

>>last few weeks I have seen many discussions over UDP truncating and using
>>"minimal-responses yes;" to prevent BIDN from doing that.
>>I've read article stating that nameserver should avoid truncating packets
>>even by skipping additional and authority sections in its responses, which
>>should mean that using minimal-responses would not help.
>>However, I've seen a few mails mentioning that a query can get truncated
>>when the authority section is too big and advices to turn
>>Reading the 9.9.2 docs and even looking at the sources (I am not a C
>>did not help me with this.

On 27.11.12 17:41, Mike Hoskins (michoski) wrote:
>It seems it should help...  less bits in the packet relating to additional
>and authority should leave room for other data.

OTOH, some of the data may be needed (later), and adding them into response
may avoid need for another request.

>That said, I think the better way (when possible) is to adjust RRs not to
>return "too much data" (e.g. NS, A, etc. not returning more than ~8 hosts
>-- which in turn could be multicast, load balanced, etc to get the desired
>Akamai, for example, defaults to limiting up to 8 "RDATAs" per RR (or
>however you'd describe that).  If you add 20 As for a name you'll rotate
>through 8 at a time.  You can request more at your own risk...they assume
>you'll ensure the larger answer will fit in a UDP packet and not cause TCP
>responses which cripple performance.

I know. But there are cases you just have much of data in the DNS and what I
am asking is, if BIND really does skip authority section, if it helps to
avoid sending truncated packets.

If it does, the minimal-responses does NOT affect packet truncation. if it
does not, I ask why...
Matus UHLAR - fantomas, uhlar at ;
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