H3C Technologies H3C S7500E Series Switches - Manual (Page 129)

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2) If the MTU supported by a forwarding interface is smaller than the packet size, the forwarding
device will discard the packet and return an ICMPv6 error packet containing the interface MTU to
the source host.
3) After receiving the ICMPv6 error packet, the source host uses the returned MTU to send packets
to the destination.
4) Step 2 to step 3 are repeated until the destination host receives the packet. In this way, the
minimum MTU of all links in the path from the source host to the destination host is determined.
Introduction to IPv6 Transition Technologies
Before IPv6 dominates the Internet, high-efficient, seamless IPv6 transition technologies are needed to
enable communication between IPv4 and IPv6 networks. There are several IPv6 transition
technologies, which can be used in different environments and periods, such as dual stack (RFC 2893),
tunneling (RFC 2893), and NAT-PT (RFC 2766).
z Dual stack is the most direct transition approach. A network node that supports both IPv4 and
IPv6 is called a dual stack node. A dual stack node configured with an IPv4 address and an IPv6
address can forward both IPv4 and IPv6 packets. For an upper layer application supporting both
IPv4 and IPv6, either TCP or UDP can be selected at the transport layer, while IPv6 stack is
preferred at the network layer. Dual stack is suitable for communication between IPv4 nodes or
between IPv6 nodes. It is the basis of all transitions technologies. However, it does not solve the
IP address depletion issue because each dual stack node must have a globally unique IP
address.
z Tunneling is an encapsulation technology, which utilizes one network protocol to encapsulate
packets of another network protocol and transfer them over the network. For more information
about tunneling, refer to Tunneling Configuration in the Layer 3 - IP Services Configuration Guide.
z Network Address Port Translation – Protocol Translation (NAPT-PT) is usually applied on a
device between IPv4 and IPv6 networks to translate between IPv4 and IPv6 packets, allowing
communication between IPv4 and IPv6 nodes. It performs IP address translation, and according
to different protocols, performs semantic translation, for packets. This technology is only suitable
for communication between pure IPv4 node and pure IPv6 node.
The S7500E series Ethernet switches do not support NAT-PT.
Protocols and Standards
Protocols and standards related to IPv6 include:
z RFC 1881: IPv6 Address Allocation Management
z RFC 1887: An Architecture for IPv6 Unicast Address Allocation
z RFC 1981: Path MTU Discovery for IP version 6
z RFC 2375: IPv6 Multicast Address Assignments