[getdns-api] EDNS maximum UDP payload size defaults to 512

[Phil Pennock]

On 2014-08-27 at 16:48 +0000, Wessels, Duane wrote:
> Hello All,
> The getdns API description says:
> 
> > getdns_return_t getdns_context_set_edns_maximum_udp_payload_size(
> >     getdns_context *context,
> >     uint16_t value
> > );
> > 
> > The value is between 512 and 65535; the default is 512.
> 
> Can someone explain why 512 should be the default value?  It seems odd
> that if the library is going to add an EDNS0 OPT record, that it should
> use the smallest possible value for the buffer size.  Software with long
> deployment history uses large values, such as 4096 and measurements from
> root/TLD name servers also indicates that 4096 is a very common value.

Broken firewalls which don't handle UDP fragment reassembly; broken
firewalls which limit port 53 UDP to 512 octets.

A client library which causes breakage, when people switch to it, will
develop a bad reputation even if the problem lies elsewhere.

-Phil
_______________________________________________
getdns-api mailing list
getdns-api at vpnc.org