3. A significant problem with supporting mobile devices on the Internet is that the Internet is designed to route packets hierarchically. The Mobile IPv4 protocol was created to address this challenge.

The most widely accepted standard for Mobile IPv4, permits a mobile device to communicate via the Internet in a relatively transparent manner.

A mobile device's IP address must change as it moves from network to network. At the same time, applications employing the TCP protocol require a constant IP address. The apparent conflict is resolved by maintaining two separate addresses for each device:

• thehome address is the natural address for the device, the one that resides in the address space of the home network. The home address is assigned by the home network itself and stays with the device long-term. With regard to TCP-based applications, this is always the IP address of the device.
• thecare-of address can potentially change from minute to minute as a device travels through several foreign networks. To the routing protocols of the Internet, this is the destination address of the device.

Any packets that are destined for the mobile device will be first routed to the home address of the device.

Additional software, termed thehome agent, will be present in a home network. The home agent is responsible for intercepting any packets addressed to mobile devices that are not currently "at home" and to then forward those packets to the current care-of address for the device. It does this by encapsulating the packet inside another packet destined for the care-of address. This packet is then sent via the Internet, where standard routing protocols ensure that it arrives at the foreign network temporarily hosting the device.

Aforeign agent unwraps the packet and sends it to the mobile device via its home address, which it has associated with a hardware destination address for the device. When the packet arrives at the device, it is accepted as being appropriately addressed; it then travels up the protocol stack to the intended TCP-based application.

a. Draw one or more diagrams showing how a computer, that is neither in the home network nor in the foreign network, can communicate with web server software running on the mobile laptop.

On your diagram(s) draw a number of relevant IP packets, and clearly show all IP addresses (included any addresses in encapsulated packets).