IPv4 address length technical design

Owen DeLong owen at delong.com
Wed Oct 3 23:15:04 UTC 2012


On Oct 3, 2012, at 3:49 PM, Jimmy Hess <mysidia at gmail.com> wrote:

> On 10/3/12, Jay Ashworth <jra at baylink.com> wrote:
>> So the address space for IPv8 will be...
>> </troll>
> 
> In 100 years, when we start to run out of IPv6 addresses,  possibly we
> will have learned our lesson and done  two things:
> 
>  (1)   Stopped  mixing the Host identification and the Network
> identification into the same bit field;   instead  every packet gets a
> source network address,  destination network address, AND  an
> additional  tuple of       Source host address,   destination host
> address;  residing in completely separate address spaces,  with  no
> "Netmasks",  "Prefix lengths", or other comingling of  network
> addresses and host address spaces.
> 

Agreed, mostly.

Prefix lengths can still be useful for route summarization and it would
be useful to have separate segments of the network address, such as
Autonomous System Number, Intra-AS Organizational Identifier, and
Intra-Organizational Network, for example. It might be useful to use
prefix lengths in those cases to allow for variability in the boundary
between these identifiers.

> And
>  (2)  The new protocol will use  variable-length address for the Host
> portion, such as  used in the addresses of CLNP,  with a convention of
> a specified length,  instead of a hardwired specific limit  that comes
> from using a permanently  fixed-width field.
> 

On this, I disagree… Once host identifiers are no longer dependent on or
related to topology, there's no reason a reasonable fixed-length cannot
suffice.

> Need more bits?   No protocol definition change required.
> 

Nope, just new ASICS everywhere and no clear way to identify where they
are or are not deployed and…

Owen




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