1. CMSC 628 - Presentation An End-to-End Approach to Host Mobility An End-to-End Approach to Host Mobility Alex C. Snoeren and Hari Balakrishnan Alex C. Snoeren and Hari Balakrishnan

2. Overview ► Introduction ► Mobile IP ► Other IP layer approaches to mobility ► Transport layer approaches ► Proposed architecture ► Issues ► Conclusions

3. Introduction ► Routing issue with legacy TCP/IP stack ► Host location and hand-off support ► End-End Vs other approaches ► Keeping mobility transparent from the transport layer

4. Mobile IP ► Essentially, mobility handled by ‘third party’ ► Triangle routing and tunneling ► Pure routing solution ► Only IP substrate changed

5. Other network layer approaches ► For the most part, enhancements of Mobile IP ► Cache care-of address of mobile host ► IPv6 mobility support

6. Transport layer approaches ► Migration NOT transparent to TCP ► Proxy approaches: transparent to sender ► Current approach

7. The End-to-End architecture ► Addressing ► Host location ► TCP connection migration ► Security

8. Host Location ► In case of fixed servers, no special service required ► In case of mobile servers, use dynamic DNS updates ► Set TTL of DNS cache entries to zero ► Problems with fast mobility

9. TCP connection migration ► Use secure tokens to identify TCP connections ► Token negotiated during handshake ► Migrate-permitted option to negotiate token ► Migrate option to migrate a connection

10. TCP connection migration

11. ► Migrate Permitted option

12. TCP connection migration ► SYN from client contains client’s public key ► Likewise for SYN from the server ► Shared secret key computed from the above ► Token computed as a hash of the shared key and initial sequence numbers

13. TCP connection migration ► Migrate option

14. TCP connection migration ► Migrate option used in the SYN after migration ► ReqNo used to order migrate requests ► Token identifies the connection ► Request is an authentication mechanism ► Essentially, hash of the initial sequence numbers, shared key, request number, and the migrate SYN segment

15. TCP connection migration ► At the other end, compare token ► Check if ReqNo is one greater than prev ► Compute request hash and compare ► Update destination address and port ► The Migrate-Wait state

16. Security ► Denial of Service ► Connection Hijacking ► Key security

17. Performance

18. Limitations ► Slow start begins after migration ► Both hosts cannot move simultaneously ► Address caching

19. Conclusions ► End-to-End architecture ► Transport layer aware of mobility ► Hosts have choice over approach used, hence more flexible ► Pretty secure ► Some limitations