ENCAPSULATION AND TUNNELING

1. ENCAPSULATION AND TUNNELING IN MOBILE IP DATA By : MD. ADIL

2. When mobile node on foriegn n/w registered with home agent The Mobile IP datagram forwarding process will be fully “activated” The home agent will intercept datagrams intended for the mobile node and forward them to the mobile node This is done by encapsulating the datagrams and then sending them to the node's care-of address.

3. Mobile IP Data Encapsulation Techniques Data exist at each layer contained within a unit called Protocol Data Unit. Data Encapsulation is a process of adding header to wrap the data flows through OSI model. The new headers specify how to send the encapsulated datagram to the mobile node's care-of address. Encapsulation is required because each datagram we intercept and forward needs to be resent over the network to the device's care-of address. The default encapsulation process used in Mobile IP is called IP Encapsulation Within IP, commonly abbreviated IP-in-IP. In addition to IP-in-IP, two other encapsulation methods may be optionally used: Minimal Encapsulation Within IP Generic Routing Encapsulation (GRE) To use either of these, the mobile node must request the appropriate method in its Registration Request The home agent must agree to use it. If foreign agent care-of addressing is used, The foreign agent also must support the method desired.

4. 5 Steps of Data Encapsulation are : The Application, Presentation & Session layer creats DATA (Message) from user's input The transport layer convers that data into SEGMENTS ( User Datagram ). The Network layer converts this Segment into PACKET (Datagram). The Data link layer converts that Packet into FRAMES. The Phyisical layer converts that Frames into BITS.

5. OSI Model & Encapsulation : Application Layer

6. OSI Model & Encapsulation : Transport Layer

7. OSI Model & Encapsulation : Network Layer

8. OSI Model & Encapsulation : Datalink Layer

9. OSI Model & Encapsulation : Physical Layer

10. OSI Model and Protocol at each layer

11. IP Data Tunneling An IP tunnel is an Internet Protocol (IP) network communications channel between two networks. It is used to transport another network protocol by encapsulation of its packets. In IP tunnelling, every IP packet, including addressing information of its source and destination IP networks, is encapsulated within another packet format native to the transit network. The borders between the source network - the transit network, the transit network - the destination network, gateways are used,that establish the end-points of the IP tunnel across the transit network The IP tunnel endpoints become native IP routers that establish a standard IP route between the source and destination networks.

12. Packets traversing these end-points from the transit network are stripped from their transit frame format headers and trailers used in the tunnelling protocol converting into native IP format and injected into the IP stack of the tunnel endpoints The tunnel represents a conductor over which datagrams are forwarded across an arbitrary internetwork, with the details of the encapsulated datagram temporarily hidden. In Mobile IP, the start of the tunnel is the home agent, which does the encapsulation.

13. The end of the tunnel depends on what sort of care-of address is being used: Foreign Agent Care-Of Address: The foreign agent is the end of the tunnel. It receives encapsulated messages from the home agent, strips off the outer IP header and then delivers the datagram to the mobile node. Co-Located Care-Of Address: The mobile node itself is the end of the tunnel and strips off the outer header.

14. Handling Tunnel Loops Loops may occur within a tunnel due to the following reasons: when the source IP of the datagram is same as the router's IP address in any of the interface. when the source IP of the datagram is same as the tunnel end point. In both the cases, the router MUST NOT tunnel the datagram. Instead it should discard the datagram. Tunnel Management: For ICMP messages intermediate routers return 64 bits of the datagram beyond the IP header which is not enough to copy Inner header. So the encapsulator will not be able to relay the appropriate message to the original sender. But this can be handled by maintaining the soft state of the tunnel. The soft state information maintained by the tunnel includes the following: MTU of the tunnel TTL of the tunnel Reachability of the decapsulator

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