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CX11x, CX31x, CX710 (Earlier Than V6.03), and CX91x Series Switch Modules V100R001C10 Configuration Guide 12

The documents describe the configuration of various services supported by the CX11x&CX31x&CX91x series switch modules The description covers configuration examples and function configurations.
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IPv6 Overview

IPv6 Overview

This section describes the definition, background, and functions of IPv6.

Definition

Internet Protocol version 6 (IPv6), also called IP Next Generation (IPng), is a second-generation network layer protocol. It was designed by the Internet Engineering Task Force (IETF) as an upgraded version of Internet Protocol version 4 (IPv4).

Purpose

IPv4 is the widely used Internet protocol. During initial development of the Internet, IPv4 rapidly developed because of its simplicity, ease of implementation, and good interoperability. However, as the Internet rapidly develops, deficiency in IPv4 design becomes obvious. To overcome the deficiency, IPv6 emerges. IPv6 has the following advantages over IPv4.

Table 6-15 Comparisons between IPv6 and IPv4

Item

Deficiency in IPv4

Advantage of IPv6

Address space

An IPv4 address is 32 bits long. A maximum of 4.3 billion IPv4 addresses can be provided. Actually, less than 4.3 billion addresses are available, and 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. Currently, IPv4 addresses are being exhausted.

There are several solutions to IPv4 address exhaustion. Classless Inter-domain Routing (CIDR) and Network Address Translator (NAT) are two such solutions. CIDR and NAT, however, have their disadvantages and unsolvable problems, which helped encourage the development of IPv6.

An IPv6 address is 128 bits long. A 128-bit address structure allows for 2128 (4.3 billion x 4.3 billion x 4.3 billion x 4.3 billion) possible addresses. The biggest advantage of IPv6 is its almost infinite address space.

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 with the Options field often need to be forwarded by intermediate devices, so many resources are occupied. Therefore, these IPv4 packets are seldom used in practice.

Compared with the IPv4 packet header, the IPv6 packet header does not carry IHL, identifier, flag, fragment offset, header checksum, option, and paddiing fields but 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. This improves IPv6 flexibility.

Autoconfiguration and readdressing

An IPv4 address is 32 bits long, and IPv4 addresses are allocated unevenly. IP addresses often need to be reallocated during network expansion or replanning. Address autoconfiguration and readdressing are required to simplify address maintenance. Currently, IPv4 depends on the Dynamic Host Configuration Protocol (DHCP) to provide address autoconfiguration and readdressing.

IPv6 provides address autoconfiguration to allow hosts to automatically discover networks and obtain IPv6 addresses. This improves network manageability.

Route summarization

Many non-contiguous IPv4 addresses are allocated, so 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. Device manufacturers have to keep upgrading devices to improve route addressing and forwarding performance.

A huge address space allows for the hierarchical network design in IPv6. The hierarchical network design facilitates route summarization and improves forwarding efficiency.

End-to-end security support

Security is not fully considered in the design of IPv4. Therefore, the original IPv4 framework does not support end-to-end security.

IPv6 supports IP Security (IPSec) authentication and encryption at the network layer, so it provides end-to-end security.

Quality of Service (QoS) support

The increasing popularity of network conferences, network telephones, and network TVs requires better QoS to ensure real-time forwarding of these voice, data, and video services. However, IPv4 has no native mechanism to support QoS.

IPv6 has the Flow Label field, which guarantees QoS for voice, data, and video services.

Mobility

As the Internet develops, mobile IPv4 experiences some problems, such as triangle routing and source address filtering.

IPv6 has the native capability to support mobility. Compared to 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 triangle routing and source address filtering in mobile IPv4. Mobile IPv6 improves mobile communication efficiency and is transparent to the application layer.

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Updated: 2019-08-09

Document ID: EDOC1000041694

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