Internet Protocol version 6 (IPv6), also called IP Next Generation (IPng), is the second-generation network layer protocol. Designed by the Internet Engineering Task Force (IETF), IPv6 is an upgraded version of Internet Protocol version 4 (IPv4).
IPv6 was developed in response to rapidly increasing Internet use. IPv4, despite being easy to implement, simple to use, and providing good interoperability, is no longer feasible as the dominant network layer protocol. This is mainly due to IPv4 address exhaustion. Table 1 shows how IPv6 overcomes many of the deficiencies found in IPv4.
Item |
Deficiency in IPv4 |
Advantage of IPv6 |
|---|---|---|
Address space |
IPv4 addresses are 32 bits long, theoretically giving an available IP address space that contains about 4.3 billion IP addresses. The currently available IP addresses are no longer sufficient to continually support the rapid expansion of the Internet. IPv4 address resources are allocated unevenly. USA address resources account for almost half of the global address space, with barely enough addresses left for Europe, and still fewer for the Asia-Pacific area. Furthermore, the development of mobile IP and broadband technologies still requires more IP addresses. The process of IP addresses being used up is known as IP address exhaustion. While several solutions to IPv4 exhaustion are currently in place, such as Classless Inter-domain Routing (CIDR) and Network Address Translator (NAT), they all have significant disadvantages. These disadvantages prompted the development of IPv6. |
IPv6 addresses are 128 bits long. A 128 bit structure allows for an address space of 2128 (4.3 billion x 4.3 billion x 4.3 billion x 4.3 billion) possible addresses. This vast address space makes it very unlikely that IPv6 address exhaustion will ever occur. |
Packet format |
The IPv4 packet header carries the Options field, including security, timestamp, and record route options. The variable length of the Options field makes the IPv4 packet header length range from 20 bytes to 60 bytes. IPv4 packets often need to be forwarded by intermediate devices. Therefore, using the Options field occupies a large amount of resources, which means this field is rarely used in practice. |
Unlike the IPv4 packet header, the IPv6 packet header does not carry IHL, identifier, flag, fragment offset, header checksum, option, or padding fields, but it carries the flow label field. This facilitates IPv6 packet processing and improves processing efficiency. To support various options without changing the existing packet format, the Extension Header information field is added to the IPv6 packet header, improving IPv6 flexibility. |
Autoconfiguration and readdressing |
IP addresses often need to be reallocated during network expansion or re-planning. Currently, IPv4 depends on Dynamic Host Configuration Protocol (DHCP) to provide address autoconfiguration and readdressing to simplify address maintenance. |
IPv6 provides address autoconfiguration to allow hosts to automatically discover networks and obtain IPv6 addresses, improving network manageability. |
Route summarization |
Many non-contiguous IPv4 addresses are allocated. Routes cannot be summarized effectively due to incorrect IPv4 address allocation and planning. The increasingly large routing table consumes a lot of memory and affects forwarding efficiency. Manufacturers must continually upgrade devices to improve route addressing and forwarding performance. |
The enormous address space allows for the hierarchical network design in IPv6 to facilitate route summarization and improve forwarding efficiency. |
End-to-end security support |
The original IPv4 framework does not support end-to-end security because security was not fully considered during the initial design. |
IPv6 supports IP Security (IPSec) authentication and encryption at the network layer, providing end-to-end security. |
Quality of Service (QoS) support |
IPv4 has no native mechanism to support QoS, especially when regarding real-time forwarding of voice, data, and video services such as network conferencing, network telephones, and network TVs. |
The Flow Label field in IPv6 guarantees QoS for voice, data, and video services. |
Mobility |
Due to the development of the Internet, mobile IPv4 experiences significant problems such as triangular routing and source address filtering. |
Mobile IPv6 improves mobile communication efficiency and is transparent to the application layer because IPv6 has the native capability to support mobility. Unlike mobile IPv4, mobile IPv6 uses the neighbor discovery function to discover a foreign network and obtain a care-of address without using any foreign agent. The mobile node and peer node can communicate using the routing header and destination options header. This function solves the problems of triangular routing and source address filtering found in mobile IPv4. |