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Chapter 22: Fundamentals of IP Version 6 525
longer receive new allocations of public addresses from IANA to then turn around and assign
smaller address blocks to companies or ISPs.
2020
ARPANET
Begins
Universities,
Research
Commerce
(.com)
1970
1980
1990
2000
2010
Pervasive
Fixed
Internet
Pervasive
Mobile
Internet
Figure 22-1
Some Major Events in the Growth of the Internet
At that point in 2011, each of the five RIRs still had public addresses to allocate or assign.
However, that same year, APNIC (Asia Pacific) became the first RIR to exhaust its available
IPv4 address allocation. In late 2015, ARIN (North America) announced that it had exhaust-
ed its supply. When we were revising this chapter in 2019, IANA considered all RIRs except
AFRINIC to have exhausted their supply of IPv4 addresses, with AFRINIC expected to run
out of IPv4 address during the year 2019.
These events are significant in that the day has finally come in which new companies can
attempt to connect to the Internet, but they can no longer simply use IPv4, ignoring IPv6.
Their only option will be IPv6 because IPv4 has no public addresses left.
NOTE
You can track ARIN’s progress through this interesting transition in the history of
the Internet at its IPv4 address depletion site: http://teamarin.net/category/ipv4-depletion/.
You can also see a summary report at http://ipv4.potaroo.net.
Even though the press has rightfully made a big deal about running out of IPv4 addresses,
those who care about the Internet knew about this potential problem since the late 1980s.
The problem, generally called the IPv4 address exhaustion problem, could literally have
caused the huge growth of the Internet in the 1990s to have come to a screeching halt!
Something had to be done.
The IETF came up with several short-term solutions to make IPv4 addresses last longer, and
one long-term solution: IPv6. However, several other tools like Network Address Translation
(NAT) and classless interdomain routing (CIDR) helped extend IPv4’s life another couple of
decades. IPv6 creates a more permanent and long-lasting solution, replacing IPv4, with a new
IPv6 header and new IPv6 addresses. The address size supports a huge number of addresses,
solving the address shortage problem for generations (we hope). Figure 22-2 shows some of
the major address exhaustion timing.
The rest of this first section examines IPv6, comparing it to IPv4, focusing on the common
features of the two protocols. In particular, this section compares the protocols (including
addresses), routing, routing protocols, and miscellaneous other related topics.
NOTE
You might wonder why the next version of IP is not called IP version 5. There was
an earlier effort to create a new version of IP, and it was numbered version 5. IPv5 did not
progress to the standards stage. However, to prevent any issues, because version 5 had been
used in some documents, the next effort to update IP was numbered as version 6.
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???
IANA
Allocates
Final /8 Block
IPv6
Replaces
IPv4
ARIN Allocates
Final IPv4 Block
Concerns
of IPv4
Address
Exhaustion
IPv4
RFC
791
IPv6
RFCs
Short Term:
NAT, CIDR
NAT, CIDR,
Defer Need
for IPv6
1980
1990
2000
2010
2015
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