3Com MSR 50 Series, Руководство по настройке

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Introduction to Tunneling 699
Figure 209 Principle of IPv4/IPv6 over IPv6 tunnel
As shown in Figure 209 , original data refers to IPv4 or IPv6 packets.
Encapsulation and decapsulation
The encapsulation process is as follows:
1
After receiving the original packet, the interface of Router A connecting private
network A submits it to the corresponding data module for processing. The data
module then determines how to route the packet.
2
If the destination of the packet is Host B connected to Router B, the packet is sent
to Router A’s tunnel interface that is connected to Router B.
3
After receiving the packet, the tunnel interface adds an IPv6 header to it and
submits it to the IPv6 module for processing.
4
The IPv6 module re-determines a route according to the destination address in the
IPv6 header.
Contrary to the encapsulation process, the decapsulation process is as follows:
1
The packet received from the IPv6 network interface is sent to the IPv6 module for
processing.
2
If the passenger protocol is IPv4 or IPv6, the packet is sent to the tunnel processing
module for decapsulation.
3
The decapsulated packet is sent to the corresponding protocol module for the
secondary route processing.
c
CAUTION: GRE can realize the IPv4/IPv6 over IPv6 tunnel function. For related
configurations, refer to “GRE Configuration” on page 1589 .
6PE Overview IPv6 on the provider edge routers (6PE) is a transition technology by which Internet
service providers (ISPs) can use existing IPv4 backbone networks to provide the
access capability for sparsely populated IPv6 networks.
The major concept of the 6PE is that the IPv6 routing information of users is
converted into IPv6 routing information with labels and is spread into IPv4
backbone networks of ISPs through internal border gateway protocol (IBGP)
sessions. When IPv6 packets are forwarded, traffic will be labeled after entering
tunnels of backbone networks. The tunnels can be GRE tunnels or MPLS LSPs.
Private
network A
IPv 6 tunnel
Private
network B
Host A Host B
IPv 6 network
Original data
IPv 6 header
Router A Router B
Original data
Original data