H3C Technologies H3C S12500 Series Switches - Manual (Page 146)

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Configuring IPv6 basics
Overview
Internet Protocol Version 6 (IPv6), also called IP next generation (IPng), was designed by the Internet
Engineering Task Force (IETF) as the successor to Internet Protocol version 4 (IPv4). The significant
difference between IPv6 and IPv4 is that IPv6 increases the IP address size from 32 bits to 128 bits.
IPv6 features
Header format simplification
IPv6 removes several IPv4 header fields or moves them to the IPv6 extension headers to reduce the length
of the basic IPv6 packet header. The basic IPv6 packet header has a fixed length of 40 bytes to simplify
IPv6 packet handling and to improve the forwarding efficiency. Although an IPv6 address size is four
times larger than an IPv4 address, the basic IPv6 packet header size is only twice the size of the
option-less IPv4 packet header.
Figure 57 IPv4 packet header format and basic IPv6 packet header format
Larger address space
The source and destination IPv6 addresses are 128 bits (or 16 bytes) long. IPv6 can provide 3.4 x 10 38
addresses to meet the requirements of hierarchical address division and the allocation of public and
private addresses.
Hierarchical address structure
IPv6 uses hierarchical address structure to quicken route searches and keep IPv6 routing tables small by
route aggregation.
Address autoconfiguration
To simplify host configuration, IPv6 supports stateful and stateless address autoconfiguration.