Hi, Christopher"
1) " IPv6 is
designed to replace IPv4. ":
Correct. But, this is not like Ten
Commandments that God gave to his children. Even such had not
worked out in most cases. In real life, technical backward
compatibility is the only known approach to achieve graceful
replacement of the old. Failing to observe such discipline, one
should not blame others for the disappointment in the
transition. I am an outsider to the Internet development
history. But, the overall appearance at this moment is that
somehow IPv6 design failed to properly execute the backward
compatibility requirement. So, IPv6 replacing IPv4 is not given.
2) Allow me to share with you an almost
parallel event in the PSTN, to illustrate how tough is to
achieve the replacement of a working service, even under an
environment with very strict backward compatibility disicpline:
A. The Decadic (rotary) Dialing (DD)
technique worked well on the telephone loop to a certain limit
of distance for many years that enabled the automatic telephone
switching systems. But, it could not go beyond the CO (Central
Office).
B. So, Bell Labs studied the use of DTMF
(Dual Tone Multi-Frequency) or commonly known as Touch-Tone as
trademarked in US, etc. The work started in mid 1940s.
c. By late 1960s, working demos became
available. During the mid-1970s, it was deployed across the Bell
System (and beyond upon requests from other countries).
D. With end-to-end signally capability of
the DTMF signalling, a lot of services such as remote purchase,
airline status checking , etc., grew drastically.
E. However, DTMF was a complete technology
from Decadic Dialing and most phones in the field were still the
latter type. COs had to install dual function line cards on the
loop that subscriber liked to enjoy the DTMF capability.
Obviously, the dual function line cards costed more than that of
the basic DD version.
F. Initially, AT&T offered the DTMF
service for free (well, covered by the rental of the new phone)
to encourage that adoption. Then, they raised the monthly
service rate for lines still requiring DD receiver hoping to
gracefully forcing the subscribes to wean from using DD phones.
G. Guess what, the inertia of the huge DD
phones out there in the field accumulated through near one
century made the strategy impossible. That is, many subscribers
would rather to pay one extra dollar or so a month to enjoy
having the old DD phone around, either to avoid paying a new
DTMF phone or just for the antique look of the DD phone. This
also created a nightmare of three types (DD, DTMF and combined)
line cards in the CO.
H. As this went on, a version of phone with
DTMF dial pad but sending out DD pulses appeared on the open
market (thanks to the deregulation / break up the Bell System).
Such novelty phones really gave phone companies a hard time
about the transition plan.
I. In the meantime, IC technology advanced
to have single chip capable of both dialing techniques (even
further integrated other traditional line card functions onto
the same chip) making the transition plan moot.
J Nowadays, almost every line card type
chip handles DTMF as advertised. But, if you try a DD phone on
it, chances are, it works anyway!
K. You may see some parallelism between the
above and the current IPv4 / IPv6 transition issues.
Regards,
Abe (2024-01-15 12:37)
On 2024-01-15 00:15,
Christopher Hawker wrote:
To my knowledge IPv6 is designed to replace IPv4.
Anyone, feel free to correct me if I'm wrong. There are just
short of 4.3 billion IPv4 addresses, where the number of IPv6
addresses is 39 digits long.
Regards,
Christopher Hawker
Hi, Randy:
1) " ... unfortunately i already had grey hair in the '90s and was in the room for all this,
... ":
My apologies! For an uninitiated, I
misread your message as if IPv6 was originally designed
with a plan to assure smooth transition from IPv4.
Regards,
Abe (2024-01-14 23:17)
On 2024-01-12 17:45, Randy Bush wrote:
Perhaps you are too young to realize that the original IPv6 plan was
not designed to be backward compatible to IPv4, and Dual-Stack was
developed (through some iterations) to bridge the transition between
IPv4 and IPv6? You may want to spend a few moments to read some
history on this.
ROFL!!! if there is anything you can do to make me that young, you
could have a very lucrative career outside of the internet.
hint: unfortunately i already had grey hair in the '90s and was in the
room for all this, and spent a few decades managing to get some of the
worst stupidities (TLA, NLA, ...) pulled out of the spec. at iij, we
rolled ipv6 on the backbone in 1997.
randy
