- Observation:
- IP packets
that are sent to a
mobile host:
- Are
first routed
towards
the home network
- And then tunneled
by the home agent to the
mobile host
- Are
first routed
towards
the home network
- IP packets
that are sent to a
mobile host:
- This
triangular route
is
not
the optimal (shortest) path
to the mobile hosts:
- To lessen (reduce) the "triangular" route inefficiency, the IP mobility solution also specifies the use of binding cache
Note:
- IP packets
from
a mobile host
does not have the
triangular route problem:
- IP packets from a mobile host follows a direct route to their destination !!!
- Bind Cache:
- Bind cache = a
table (data structure)
containing entries of the following
format:
HostIP | CareOfNode ===============+================= 10.0.0.4 | 12.0.0.1
Purpuse of the binding cache:
- "correspondent nodes may
cache the binding
of a mobile node, and then tunnel
their datagrams for the mobile node
directly
to the care-of address,
bypassing the mobile node's home
agent."
See the abstract on IETF draft: click here
Route Optimization in Mobile IP: click here
- Bind cache = a
table (data structure)
containing entries of the following
format:
- How to use
a binding cache:
if ( destIP Address ∈ BindCache ) { tunnel IP packet to the CareOfNode; } else { perform IP routing on destIP Address; }
- Example:
IP forwarding
with a binding cache
- Suppose the node 11.0.0.7
has the following binding cache
content:
- Suppose the
node 11.0.0.7
sends an
IP packet to
(the mobile host)
10.0.0.4:
- The binding cache entry
(10.0.0.4, 12.0.0.1) will
cause encapsulation (tunneling):
- Suppose the node 11.0.0.7
has the following binding cache
content: