Operation Manual

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2. Header format simplification: IPv6 cuts down some IPv4 header fields or move them to
IPv6 extension headers to reduce the load of basic IPv6 headers, 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).
3. Flexible extension headers: IPv6 cancels the Options field in IPv4 packets but introduces
multiple extension headers. In this way, IPv6 enhances the flexibility greatly to provide
scalability for IP while improving the handling efficiency. The Options field in IPv4 packets
contains 40 bytes at most, while the size of IPv6 extension headers is restricted by that of
IPv6 packets.
4. 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.
5. 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.
6. Enhanced neighbor discovery mechanism: The IPv6 neighbor discovery protocol is a
group of Internet control message protocol version 6 (ICMPv6) messages that manages
the information exchange between neighbor nodes on the same link. The group of ICMPv6
messages takes the place of Address Resolution Protocol (ARP) message, Internet Control
Message Protocol version 4 (ICMPv4) router discovery message, and ICMPv4 redirection
message to provide a series of other functions.
 Introduction to IPv6 address
1. IPv6 address format
An IPv6 address is represented as a series of 16-bit hexadecimals, separated by colons (:).
An IPv6 address is divided into eight groups, and the 16 bits of each group are represented
by four hexadecimal numbers which are separated by colons, for example,
2001:0d02:0000:0000:0014: 0000:0000:0095. The hexadecimal letters in IPv6 addresses
are not case-sensitive.
To simplify the representation of IPv6 addresses, zeros in IPv6 addresses can be handled
as follows: