RFC 2473 (rfc2473) - Page 8 of 36
Generic Packet Tunneling in IPv6 Specification
Alternative Format: Original Text Document
RFC 2473 Generic Packet Tunneling in IPv6 December 1998
For example, in the case the Next Header field has the IPv6 Tunnel
Protocol value, the resulting original packet is passed to the IPv6
protocol layer.
The tunnel exit-point node, which decapsulates the tunnel packets,
and the destination node, which receives the resulting original
packets can be the same node.
3.4 IPv6 Tunnel Protocol Engine
Packet flow (paths #1-7) through the IPv6 Tunnel Protocol Engine on a
node is graphically shown in Fig.5:
Note:
In Fig.5, the Upper-Layer Protocols box represents transport
protocols such as TCP, UDP, control protocols such as ICMP, routing
protocols such as OSPF, and internet or lower-layer protocol being
"tunneled" over IPv6, such as IPv4, IPX, etc. The Link-Layer
Protocols box represents Ethernet, Token Ring, FDDI, PPP, X.25, Frame
Relay, ATM, etc..., as well as internet layer "tunnels" such as IPv4
tunnels.
The IPv6 tunnel protocol engine acts as both an "upper-layer" and a
"link-layer", each with a specific input and output as follows:
(u.i) "tunnel upper-layer input" - consists of tunnel IPv6 packets
that are going to be decapsulated. The tunnel packets are
incoming through the IPv6 layer from:
(u.i.1) a link-layer - (path #1, Fig.5)
These are tunnel packets destined to this node and will
undergo decapsulation.
(u.i.2) a tunnel link-layer - (path #7, Fig.5)
These are tunnel packets that underwent one or more
decapsulations on this node, that is, the packets had
one or more nested tunnel headers and one nested tunnel
header was just discarded. This node is the exit-point
of both an outer tunnel and one or more of its inner
tunnels.
For both above cases the resulting original packets are passed
back to the IPv6 layer as "tunnel link-layer" output for
further processing (see b.2).
Conta & Deering Standards Track