Ipv6 Features - H3C S5500-SI Series Operation Manual

Operation Manual – IPv6
H3C S5500-SI Series Ethernet Switches

1.1.1 IPv6 Features

I. Header format simplification
IPv6 cuts down some IPv4 header fields or move them to the IPv6 extension headers to
reduce the length of the basic IPv6 header. IPv6 uses the basic header with a fixed
length, thus making IPv6 packet handling simple and improving the forwarding
efficiency. Although the IPv6 address size is four times that of IPv4 addresses, the size
of basic IPv6 headers is 40 bytes and is only twice that of IPv4 headers (excluding the
Options field).
0 3
Ver HL
Identification
TTL
Figure 1-1 Comparison between IPv4 packet header format and basic IPv6 packet
header format
II. Adequate address space
The source and destination IPv6 addresses are both 128 bits (16 bytes) long. IPv6 can
provide 3.4 x 10
address division as well as allocation of public and private addresses.
III. 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.
IV. 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).
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ToS Total length
F Fragment offset
Protocol Header checksum
Source address (32 bits)
Destination address (32 bits)
Options
IPv4 header
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addresses to completely meet the requirements of hierarchical
Chapter 1 IPv6 Basics Configuration
31 0 3
Traffic
Ver
class
Payload length
Source address (128 bits)
Padding
Destination address (128 bits)
1-2
11 15 23
Flow label
Next
Hop limit
header
Basic IPv6 header
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