Explain IP packet delivery.

Subject: Mobile Communication and Computing

Topic: Mobile Network

Difficulty: Low

1 Answer

The mobile i.e movement of MN from one location to another has to be hidden as per the requirement of mobile IP. CN may not know the exact location of MN

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STEP 1: CN sends the packet as usual to the IP address of MN. With Source address as CN and Destination address as MN .The internet, which does not have any information of the current location of MN, routes the packet to the router responsible for the home network of MN. This is done using the standard routing mechanisms of the internet.

STEP 2: The HA now diverts the packet, knowing that MN is currently not in its home network. The packet is not forwarded into the subnet as usual, but encapsulated and tunnelled to the COA. A new header is put in front of the old IP header showing the COA as new destination and HA as source of the encapsulated packet.

STEP 3: The foreign agent (FA) now decapsulates the packet, i.e., removes the additional header(newly added as COA as destination and HA as source), and forwards the original packet with CN as source and MN as destination to the MN. Again, for the MN mobility is not visible.

Finally the MN Receives the packet with the Source address as CN and Destination address as MN.

STEP 4: The MN sends the packet MN as Source Address and CN as Destination Address. The router with the FA acts as default router and forwards the packet in the same way as it would do for any other node in the foreign network. Simple mechanism works if CN is Fixed at a location if it has got mobility then the above Steps 1 to 3 are to be followed to deliver the packet from MN to CN.

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