Joel> Given that LISP ITRs work by intercepting packets that are
Joel> not addressed to them, a host implementation would need to
Joel> be able to intercept packets "in the stack". That is going
Joel> to need some ability to modify kernel behavior.
I'm trying to figure out how an ITR does anything different than a
router with a tunneled interface.
It doesn't. I mean there are subtleties about if a map-cache entry
exists and what to do when it doesn't. But if a map-cache entry exists
it is similar to a packet arriving on an interface and is sent on a
GRE tunnel. There are implementation details that make it different,
but from a conceptual level, they are the same.
Every host I'm aware of has a facility for setting up an interface
that routes some set of packets--including potentially the default
route--through a tunnel interface that then passes the packet to
userspace for processing.
We call "LISP tunnels" as "dynamic encapsulating tunnels" where an
implementation must not implement the tunnel as a logical interface.
The implementation cannot scale if it does this. You get the level of
indirection by doing another lookup in another data structure called
the "map-cache".
Dino
--------------------------------------------------------------------
IETF IPv6 working group mailing list
ipv6@ietf.org
Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6
--------------------------------------------------------------------
