500 CHAPTER 38: IPV6 BASICS CONFIGURATION
addresses, the size of basic IPv6 headers is 40 bytes and is only twice that of IPv4
headers (excluding the Options field).
Figure 150 Comparison between IPv4 packet header format and basic IPv6 packet header
format
Adequate address space
The source and destination IPv6 addresses are both 128 bits (16 bytes) long. IPv6
can provide 3.4 x 10
38
addresses to completely meet the requirements of
hierarchical address division as well as allocation of public and private addresses.
Hierarchical address structure
IPv6 adopts the hierarchical address structure to quicken route search and reduce
the system source occupied by the IPv6 routing table by means of route
aggregation.
Automatic address configuration
To simplify the host configuration, IPv6 supports stateful and stateless address
configuration.
■ Stateful address configuration means that a host acquires an IPv6 address and
related information from a server (for example, DHCP server).
■ Stateless address configuration means that a host automatically configures an
IPv6 address and related information on basis of its own link-layer address and
the prefix information advertised by a router.
In addition, a host can generate a link-local address on basis of its own link-layer
address and the default prefix (FE80::/64) to communicate with other hosts on the
link.
Built-in security
IPv6 uses IPSec as its standard extension header to provide end-to-end security.
This feature provides a standard for network security solutions and improves the
interoperability between different IPv6 applications.
Ver
0113
Traffic
class
Flow label
Payload length
Next
header
Hop limit
Source address (128 bits)
Destination address (128 bits)
3115 23
Ver HL ToS Total length
0733115 23
Identification Fragment offsetF
TTL Protocol Header checksum
Source address (32 bits)
Destination address (32 bits)
Options Padding
IPv4 header
Basic IPv6 header
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