[LEAPSECS] Bulletin C and all that

[Zefram]

Peter Vince wrote:
>Class E addresses?

IPv4 address space is for some purposes divided into five classes:
class A is 0.0.0.0/1, class B is 128.0.0.0/2, class C is 192.0.0.0/3,
class D is 224.0.0.0/4, and class E is 240.0.0.0/4.  Classes A, B, and
C form the unicast address space, originally with subnet sizes linked
to the classes but now with no real class distinction.  Class D is the
multicast address space.  Class E, apart from the limited-broadcast
address 255.255.255.255, remains reserved for future use.

The class terminology is technically obsolete, but still common.  See,
for example, RFC 5735, which describes the 240.0.0.0/4 block as "formerly
known as the Class E address space" and "reserved for future use".
The current iteration of that standard, RFC 6890, doesn't even mention
the classful terminology.

>and mention of A, AAA, and AAAA means nothing to me :-(

"AAA" would be a typo for "AAAA".  These are DNS resource record types.
An A record contains an IPv4 address, and an AAAA record contains an
IPv6 address.  IPv6 addresses are four times the size of IPv4 addresses,
hence the name.  The fundamentals of the DNS are specified by RFC 1034
and RFC 1035 (the latter including the A type), and the AAAA type is
specified by RFC 3596.

-zefram