- Home network:
- Home network = the IP network of the mobile host
- Foreign network:
- Foreign network = the IP network that the mobile host is visiting
- Special
mobility support
agents:
- Home Agent =
a router
at mobile host's
home network
that is:
- Running a special mobile IP software.
- Home Foreign Agent =
a router at a
foreign IP network
that the mobile host
visits
that
is:
- Running a special mobile IP software.
- Home Agent =
a router
at mobile host's
home network
that is:
- Detecting
the presence and identifty of
(special) agents:
-
(Home/foreign) Agents
(= routers with
IP mobility support)
will:
- Periodically broadcast a agent advertising message
-
(Home/foreign) Agents
(= routers with
IP mobility support)
will:
- Requirement
for support for
IP mobility:
- One of the routers in the home network must become a home agent
- In the
Foreign agent
solution:
- One of the
routers
in the
Foreign network
must be:
- A foreign agent
- One of the
routers
in the
Foreign network
must be:
- Mobile IP
RFC:
- The details of IP mobility technique are specified in the Internet document RFC 2002: click here
- Preparing to
become mobile:
- Before
the nomadic host
leaves its
home network:
- The
nomadic host must
listen
for
agent advertising messages
on its home network
- The nomadic host must record the IP address of a home agent.
Graphically:
- The
nomadic host must
listen
for
agent advertising messages
on its home network
- Before
the nomadic host
leaves its
home network:
- The Foreign Agent solution:
- When the nomadic host
arrives at a foreign
network:
- The nomadic host will listen for agent advertising messages on the foreign network
Graphically:
When the mobile host receives a agent advertising message:
- The mobile host will record the IP address of the Foreign agent.
- The mobile host then:
- The moble host sends a
Register message
to
its foreign agent containing:
- The mobile host's IP address
- The home agent's IP address
Graphically:
- The moble host sends a
Register message
to
its foreign agent containing:
- When the foreign agent
receives the
Register message:
- Enter the
IP address of the
mobile host
into a CareOf table
- The Foreign Agent sends a
CareOf message
to the home agent
of the mobile host containing:
- IP address of the mobile host
- IP address of the Foreign Agent
Graphically:
- Enter the
IP address of the
mobile host
into a CareOf table
- When the home agent
receives
the
CareOf message:
- The home agent creates an IP tunnel to the foreign agent
The tunnel is created by adding the following virtual entry into its Forwarding table:
Destination | Next ----------------------------+--------------------------------- IP address of moble host | IP address of foreign agentExample:
- When the nomadic host
arrives at a foreign
network:
- Result of the
registering operation:
- We have create a
IP-in-IP yunnel:
- We have create a
IP-in-IP yunnel:
- Notice that:
- The tunnel is unidirectional (only from home agent to foreign agent).
- You will see later
that:
- The reverse direction of the tunnel is not necessary !!!!