generic v6 tunneling

[Steve Deering]

At 9:33 AM +0000 2/6/02, IPSix  Developer wrote:
>1)With ref to section 3.3 of RFC 2473 :
>
"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".
>
>Does it mean tunnel exit-point IPv6 address and original packets
>destination IPv6 address are same?

Possibly, but not necessarily.  If the tunnel is treated as a separate
link, the exit endpoint of the tunnel will have its own IPv6 address(es),
distinct from those of the physical interface at which the tunnel
terminates.  But is also perfectly "legal" to send an IPv6 packet
encapsulated within another IPv6 packet, in which both the inner
and outer destination addresses are the same.
>
> If they are same, how do we configure
>the route for the destination V6 address at the tunnel entry point?

That is just an example of a router with more than one path to the same
destination.  That is handled as normal, either using routing protocols
to choose the "shortest" or "best" path, or by configuration (a "static
route").  

>2)With ref to section 7.1(a) of RFC 2473:
>
>When the IPv6 packet size is larger than IPv6 min link MTU, the ICMPv6
>pkt too big msg is sent with MTU as max(tunnel MTU, IPv6 min link MTU) .
>
>If the furthur received packets' size is larger than IPv6 min link MTU,
>again TOO BIG message will be sent and a looping will occur? how to
>avoid this?

If the source node ignores the Packet Too Big message and continues to
send packets that exceed max(tunnel MTU, IPv6 min link MTU), those
packets will be dropped and will trigger additional Packet Too Big
messages, subject to the general rate limiting requirement imposed
on transmitting ICMP error messages.

Steve