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facing the present scale and complexity of Internet.
IPv6 refers to the sixth version of Internet protocol which is the next generation
Internet protocol designed by IETF to replace the current Internet protocol version 4
(IPv4). IPv6 was specially developed to make up the shortages of IPv4 so that Internet
can develop further.
The most important problem IPv6 has solved is to add the amount of IP address.
IPv4 addresses have nearly run out, whereas the amount of Internet users has been
increasing in geometric series. With the greatly and continuously boosting of Internet
services and application devices (Home and Small Office Network, IP phone and
Wireless Service Information Terminal which make use of Internet,) which require IP
addresses, the supply of IP addresses turns out to be more and more tense. People have
been working on the problem of shortage of IPv4 addresses for a long time by
introducing various technologies to prolong the lifespan of existing IPv4 infrastructure,
including Network Address Translation(NAT for short), and Classless Inter-Domain
Routing(CIDR for short), etc.
Although the combination of CIDR, NAT and private addressing has temporarily
mitigated the problem of IPv4 addresses space shortage, NAT technology has disrupted
the end-to-end model which is the original intention of IP design by making it necessary
for router devices that serve as network intermediate nodes to maintain every connection
status which increases network delay greatly and decreases network performance.
Moreover, the translation of network data packet addresses baffles the end-to-end
network security check, IPSec authentication header is such an example.
Therefore, in order to solve all kinds of problems existing in IPv4 comprehensively,
the next generation Internet Protocol IPv6 designed by IETF has become the only
feasible solution at present.
First of all, the 128 bits addressing scheme of IPv6 Protocol can guarantee to
provide enough globally unique IP addresses for global IP network nodes in the range of
time and space. Moreover, besides increasing address space, IPv6 also enhanced many
other essential designs of IPv4.
Hierarchical addressing scheme facilitates Route Aggregation, effectively reduces
route table entries and enhances the efficiency and expansibility of routing and data
packet processing.
The header design of IPv6 is more efficient compared with IPv4. It has less data
fields and takes out header checksum, thus expedites the processing speed of basic
IPv6 header. In IPv6 header, fragment field can be shown as an optional extended field,
so that data packets fragmentation process won’t be done in router forwarding process,
and Path MTU Discovery Mechanism collaborates with data packet source which
enhances the processing efficiency of router.
