R0106-HP MSR Router Series Layer 3 - IP Services Configuration Guide(V7)

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d. The IPv6 protocol stack uses the destination IPv6 address of the packet to look up the routing
table, and then sends it out.
• De-encapsulation:
e. Upon receiving the IPv6 packet from the attached IPv6 network, Device B delivers the packet
to the IPv6 protocol stack to examine the protocol type encapsulated in the data portion of the
packet.
f. If the protocol type is IPv4, the IPv6 protocol stack delivers the packet to the tunneling module.
g. The tunneling module removes the IPv6 header and delivers the remaining IPv4 packet to the
IPv4 protocol stack.
h. The IPv4 protocol stack forwards the IPv4 packet.
Tunnel modes
IPv4 over IPv6 tunnels include the following modes:
• IPv4 over IPv6 manual tunnel
A point-to-point link and its source and destination IPv6 addresses are manually configured. You
can establish an IPv4 over IPv6 manual tunnel to connect isolated IPv4 networks over an IPv6
network.
• DS-Lite tunnel
Dual Stack Lite (DS-Lite) is a combination of the tunneling and NAT technologies. NAT translates
the private IPv4 addresses of the IPv4 hosts before the hosts reach the IPv4 public network.
DS-Lite tunnel supports only an IPv4 host in a private network initiating communication with an IPv4
host on the Internet. It does not support an IPv4 host on the Internet initiating communication with
an IPv4 host in a private network.
Figure 108 DS-Lite tunnel
As shown in Figure 108, the DS-Lite feature contains the following components:
{ Basic Bridging BroadBand (B4) element
The B4 element is typically a CPE router that connects end hosts. IPv4 packets entering the B4
router are encapsulated into IPv6 packets and sent to the AFTR. IPv6 packets from the AFTR are
de-encapsulated into IPv4 packets and sent to the subscriber's network.
Hosts that can serve as the B4 router are referred to as DS-Lite hosts.