Max. Number of char in a TXT Record

Leonard Mills lenm at yahoo.com
Fri Mar 27 00:10:33 UTC 2009


Darvin Denmian asked:
> 2) What is the maximum number of includes inside a SFP field?

It is RECOMMENDED that SPF library implementations limit the number of DNS operations performed during a lookup to ten, to cut down on the chances of a denial-of-service exercise using SPF and to short-circuit any possible include loops.  Each lookup counts, and a lookup of an include is no exception to this rule.

If there were nothing in the base record beyond IP ranges and one or more includes, and all of the includes provided records with only IP ranges and possibly other includes, then ten total includes should be expected to work.  Stick in a ptr clause (or anything else calling for a new DNS operation), and the number of potential includes decreases.

Hope this helps,

Len



      



More information about the bind-users mailing list