3Com MSR 50 Series Configuration Manual page 656

656 C 46: IP 6 B
HAPTER V ASICS
C
ONFIGURATION
addresses, the size of basic IPv6 headers is 40 bytes and is only twice that of IPv4
headers (excluding the Options field).
Figure 194 Comparison between IPv4 packet header format and basic IPv6 packet header
format
0 3 7 15
Ver HL ToS
Identification
TTL Protocol
Source address (32 bits)
Destination address (32 bits)
Options
IPv4 header
Adequate address space
The source and destination IPv6 addresses are both 128 bits (16 bytes) long. IPv6
can provide 3.4 x 10 38
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 the basis of its own link-layer address
and the prefix information advertised by the router.
In addition, a host can generate a link-local address on the basis of its own
link-layer address and the default prefix (FE80::/64) to communicate with other
hosts on the same 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.
23 31 0
Total length Ver
F Fragment offset
Header checksum
Padding
addresses to completely meet the requirements of
3 11 15
Traffic
Flow label
class
Next
Payload length
header
Source address (128 bits)
Destination address (128 bits)
Basic IPv 6 header
23 31
Hop limit