So... is it time to do IPv6 day monthy yet?

Jimmy Hess mysidia at gmail.com
Sat Jun 18 10:00:46 CDT 2011


On Sat, Jun 18, 2011 at 4:31 AM, Mark Andrews <marka at 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




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