Packet sizes in DNSSEC (08 Mar 2009)

Even when the DNS root hasn't started signing records, one can still use trust-anchors to employ DNSSEC for those TLDs which support it. Follow the links from Ben Laurie's latest blog post on the matter.

The .se ccTLD is one of those TLDs which support DNSSEC. You can test it with: dig +dnssec -t any se You'll see lots of NSEC, RRSIG and DNSKEY records. (DNSSEC is very complicated.)

However, the size of that reply is 3974 bytes long! All that from a request packet of 31 bytes. That's a very easy to use 100x DoS amplication. Of course, if you use mirror amplication like that, you cannot forge the source addresses of the flooding packets, making the flood easier to filter. However, DNSSEC may well bring DoS floods into the reach of many more attackers.