Ralph Droms wrote:
Brian - is it provable that no design for a follow-on to IPv4 would have
provided that backward compatibility? Or were there architectural and
engineering decisions that chose other features over backward
compatibility?
1. Take the original, simple Deering specification.
2. Declare the initial IPv6 address space as being the current IPv4
address space, with all upper bits zero.
3. The requirement for connecting a v6 stack to a v4 stack is a very
simple IP header-mapping translation, with no loss of information at the IP
level.
4. The v6 stack would need to have a v4 mode, for use by v4 applications
-- applications that use v4 addresses.
You are now done with an initial v6 deployment.
Note the absence of dual stack in any single host, the minimal incompatibility
between the two versions of IP, and so on.
A continuing series of incremental changes would permit incremental benefit of
the larger address space in IP, routing, applications, etc.
Has the added 15 years brought more functionality than this approach would
have permitted? Is deployment easier?
d/
--
Dave Crocker
Brandenburg InternetWorking
bbiw.net
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