- This is hooking a laptop to a Cell phone through a modem...
- Works, but uses dedicated equipment: does not work across different cell phone providers...
- What's the problem with IP routing when applied to a mobile host ???
Consider this example where a host (11.0.0.7) sends an IP packet to the mobile host (10.0.0.4) while the mobile host has not yet moved:
Suppose the mobile host (10.0.0.4) moved to another network (say, network (12.0.0.xx)):
You can see the problem immediately:
- IP routes using network ID information
- Packet destined for 10.0.0.4 will travel to the 10.0.0.0 network and will not reach the intended host
- IP routes using network ID information
- Yes, that will work.
- But the solution can hardly be called a "mobile solution" because:
- Everytime the mobile host moves to another network and receives
a new (suitable) IP address,
every existing active TCP connection in
the mobile host will become
unusable
Imagine have to login to several telnet sessions each time you move to a different service area... you would rather roam with a cell phone attached to your laptop...
- Everytime the mobile host moves to another network and receives
a new (suitable) IP address,
every existing active TCP connection in
the mobile host will become
unusable
- Must allow an IP host to maintain all existing (TCP) connections
- Must work
without having to change the IP software in existing
non-mobile hosts.
- Must work
without having to change the IP software
in
most
IP routers
That is because (the Internet is huge and international... if the solution can only work when most of the routers need to be upgraded, you may as well toss the solution away - cause it ain't gonna happen.
- Solution 1 uses 2 special agents: home & foreign agents
- Solution 2 uses the home agent and the DHCP protocol.