- What does
it mean to
provide
mobility support at the
IP layer:
- An IP host/node is able to move between IP networks without the interruption of existing network connections
Example:
- Mobile host has a
connection to another
host:
- After the
mobile host
traveled to another IP network:
Then:
- All existing connections must not be interrupted
- Consider a
concrete example:
- A mobile host (10.0.0.4)
(on IP network 10.0.0.xx)
has a connection with the
host (11.0.0.7):
- After the
mobile host (10.0.0.4)
moved to another network:
Result:
- The mobile host
cannot receive
messages
- The existing connections have been interrupted !!!
- The mobile host
cannot receive
messages
- A mobile host (10.0.0.4)
(on IP network 10.0.0.xx)
has a connection with the
host (11.0.0.7):
-
The gist
of the IP mobility problem:
- Routing at the
network level
is based on the
destination IP address
in the packet
- Therefore:
- When the mobile host
travels to another IP network:
- The TCP message will still be routed to the home IP network of the mobile IP host !!!
- When the mobile host
travels to another IP network:
- Routing at the
network level
is based on the
destination IP address
in the packet
- Example:
- When the
mobile host 10.0.0.4 travels to
network 12.0.0.x,
it is assigned a
new IP address 12.0.0.8:
Nodes must use the new IP address to reach thje mobile host
- When the
mobile host 10.0.0.4 travels to
network 12.0.0.x,
it is assigned a
new IP address 12.0.0.8:
- This "solution"
will not work:
- TCP connections are
stateful:
- You cannot change the TCP state after the TCP connection has been established
- TCP connections are
identified by:
(SrcIP, SrcPort#, DestIP, DestPort#)
- Therefore:
- Existing TCP connection
must
continue to
use the
same
(DestIP, DestPort#):
Result:
- Existing TCP connections will be interrupted !!!
- Existing TCP connection
must
continue to
use the
same
(DestIP, DestPort#):
- TCP connections are
stateful:
- Constraints on
Network Level
mobile IP solution:
- Must allow an
IP host
to maintain
existing TCP connections
- Must work
without having to replace
the IP software in existing
non-mobile hosts.
- The solution should not require
all IP host software to
be upgraded
- The solution should only require the mobile IP hosts to be upgraded their IP software
- The solution should not require
all IP host software to
be upgraded
- Must work
without
having to replace
the IP software
in
non-related routers
- The solution should not require
all IP routers to
be upgraded
- The solution should only require the IP routers that want to provide IP mobility to upgrade their IP software
- The solution should not require
all IP routers to
be upgraded
- Must allow an
IP host
to maintain
existing TCP connections
- There are 2 solutions for the
network level
mobile IP support:
- The home agent plus the
foreign agent solution
- The home agent plus the DHCP protocol solution
- The home agent plus the
foreign agent solution