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Why IPv6 is Required
Internet Protocol Version 6 (IPv6), complies with a set of specifications defined by the Internet Engineering Task Force (IETF), IPv6 is an upgrade of Internet Protocol Version 4 (IPv4). The most significant difference between IPv6 and IPv4 is that the length of IP addresses is extended from 32 bits to 128 bits in IPv6. Featuring a simplified header format, sufficient address space, layered address structure, flexible extension header, and enhanced neighbor discovery (ND) mechanism, IPv6 is more competitive in the future market.
As the IPv4-based Internet achieves great success, the IP technology is widely applied. With the rapid development of the Internet, however, deficiencies of IPv4 are more strongly felt, especially in the following aspects:
1. The IPv4 address space is insufficient.
An IPv4 address is identified by using 32 bits. In theory, a maximum of 4.3 billion addresses can be provided. In practice, less than 4.3 billion addresses are available due to address allocation reasons. In addition, IPv4 address resources are allocated unevenly. The USA uses almost half of the world's IP addresses, while Europe uses fewer IP addresses than the USA and the Asian-Pacific region uses even fewer. The development of mobile IP and broadband technologies requires more IP addresses. The shortage of IPv4 addresses directly restricts further development of the IP technology.
There are several solutions to IPv4 address shortage. Classless Inter-domain Routing (CIDR) and Network Address Translation (NAT) are two major solutions. CIDR and NAT, however, have their disadvantages and outstanding problems. This also drives the need for and the development of IPv6.
2. The backbone device needs to maintain a large number of routing entries.
Due to allocation and planning problems in the early phase of IPv4 development, many discontinuous IPv4 addresses are allocated and as a result routes cannot be aggregated effectively. The increasingly large routing tables consume a lot of memory, leading to higher costs for equipment and lower forwarding efficiency. To tackle these issues, device manufacturers have to constantly upgrade their products in order to improve route addressing and forwarding performance.
3. Address autoconfiguration and readdressing cannot be performed easily.
An IPv4 address occupies only 32 bits and IP addresses are allocated unevenly. Consequently, IP addresses need to be reallocated during network expansion or network replanning. Address autoconfiguration and readdressing are required to simplify maintenance. With IPv4, however, such tasks cannot be performed easily.
4. Security cannot be well guaranteed.
With the development of the Internet, security problems become more serious. During the design of IPv4, security was not fully considered. Hence, the original framework cannot implement end-to-end security. IPv6 provides end-to-end security.
IPv6 solves the IP address shortage issue from the very outset. Moreover, IPv6 is easy to deploy, compatible with various applications, allows IPv4 networks to smoothly transit to IPv6 networks, and can coexist and interwork with IPv4. With so many advantages over IPv4, IPv6 is in rapid development.
IPv6 network deployment
Internet protocol version 6 (IPv6) is developed to tackle global IPv4 address shortage. At the early stage of IPv4-to-IPv6 transition, IPv4 networks have been in large-scale deployment whereas deployment of IPv6 networks is comparatively scarce, and both types of networks will coexist. The following figure shows the IPv6 network deployment in the early stages of the IPv4-to-IPv6 transition.
Pv4-based broadband remote access servers (BRASs) on the live network are progressively upgraded to support IPv4/IPv6 dual-stack. The dual-stack BRAS provides a 6in4 tunnel or a dedicated link to transmit IPv6 traffic to an IPv6 network.
The dual-stack BRAS provides the network address translation-protocol translation (NAT-PT) function to allow IPv6 users to access an IPv4 network.
The access network equipment is able to detect IPv6 packets, allocate IPv6 addresses (using DHCPv6), and support ACLv6.
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