On Sat, Jun 18, 2011 at 4:31 AM, Mark Andrews <marka@isc.org> wrote:
Not really. A AAAA record adds 28 octets (a A record takes 16). Unless you have a lot of name servers most referrals still fall within 512 octets additionally most answers also still fall withing 512 octets.
I agree.. not that it should be assumed there is no v6 DNS issue. With IPv6, the main issue may be 'firewalls' and 'boxes in the middle' silently munging, eating, or destroying AAAA responses. DNSSEC and not AAAA is really the reason to have need for EDNS0 or TRUNC on validating resolvers. AAAA records should be fine for sane domains. consider a referral for example.com -> subdomain.example.com with 8 nameservers. mydomainname.example.com; and assume you get both AAAA and A additional responses. Total = 402 octets -- still safe; your domain name could be ~100 characters longer and it would still be fine. Header < 2 (id) + 2 (qr,opcode,aa,tc,rd,ra,z,rcode,qdcount) + 2 (ancount) + 2 (nscount) + 2 (arcount) = 10 octets Authority Section ns1.subdomain.example.com. IN NS ns1.subdomain.example.com. < 26name + 2 + 2 + 4 + 2 + 2(pointer) = 36 octets ns2.subdomain.example.com. IN NS ns2.subdomain.example.com. < 4 name + 2(pointer) + 2 + 2 + 4 + 2 +2(pointer) = 18 octets ns3.subdomain.example.com. IN NS ns3.subdomain.example.com. < 4 name + 2 + 2 + 2 + 4 + 2 + 2 = 18 octets ns4.subdomain.example.com. IN NS ns4.subdomain.example.com. < 18 octets ns5.subdomain.example.com. IN NS ns5.subdomain.example.com. < 18 octets ns6.subdomain.example.com. IN NS ns6.subdomain.example.com. < 18 octets ns7.subdomain.example.com. IN NS ns7.subdomain.example.com. < 18 octets ns8.subdomain.example.com. IN NS ns8.subdomain.example.com. < 18 octets Additional Section ns1.subdomain.example.com. IN AAAA 2001:DB8::0 < 2(pointer) +4TTL+2RDLENGTH+16RDATA = 24 octets ns2.subdomain.example.com. IN AAAA 2001:DB8::1 < 24 octets ns3.subdomain.example.com. IN AAAA 2001:DB8::2 < 24 octets ns4.subdomain.example.com. IN AAAA 2001:DB8::3 < 24 octets ns5.subdomain.example.com. IN AAAA 2001:DB8::4 < 24 octets ns6.subdomain.example.com. IN AAAA 2001:DB8::5 < 24 octets ns7.subdomain.example.com. IN AAAA 2001:DB8::6 < 24 octets ns8.subdomain.example.com. IN AAAA 2001:DB8::7 < 24 octets ns1.subdomain.example.com. IN A 192.0.0.0.1 < 2(pointer) +4TTL+2RDLENGTH+4RDATA = 12 octets ns2.subdomain.example.com. IN A 192.0.0.0.1 < 12 octets ns3subdomain.example.com. IN A 192.0.0.0.1 < 12 octets ns4.subdomain.example.com. IN A 192.0.0.0.1 < 12 octets Total = 402 octets -- still safe; your domain name could be ~100 characters longer and it would still be fine. -- -JH