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CMSC 628 - Presentation. An End-to-End Approach to Host Mobility Alex C. Snoeren and Hari Balakrishnan. Overview. Introduction Mobile IP Other IP layer approaches to mobility Transport layer approaches Proposed architecture Issues Conclusions. Introduction.

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CMSC 628 - Presentation

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CMSC 628 - Presentation

An End-to-End Approach to Host Mobility

Alex C. Snoeren and Hari Balakrishnan


Overview

  • Introduction

  • Mobile IP

  • Other IP layer approaches to mobility

  • Transport layer approaches

  • Proposed architecture

  • Issues

  • Conclusions


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


Mobile IP

  • Essentially, mobility handled by ‘third party’

  • Triangle routing and tunneling

  • Pure routing solution

  • Only IP substrate changed


Other network layer approaches

  • For the most part, enhancements of Mobile IP

  • Cache care-of address of mobile host

  • IPv6 mobility support


Transport layer approaches

  • Migration NOT transparent to TCP

  • Proxy approaches: transparent to sender

  • Current approach


The End-to-End architecture

  • Addressing

  • Host location

  • TCP connection migration

  • Security


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


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


TCP connection migration


TCP connection migration

  • Migrate Permitted option


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


TCP connection migration

  • Migrate option


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


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


Security

  • Denial of Service

  • Connection Hijacking

  • Key security


Performance


Limitations

  • Slow start begins after migration

  • Both hosts cannot move simultaneously

  • Address caching


Conclusions

  • End-to-End architecture

  • Transport layer aware of mobility

  • Hosts have choice over approach used, hence more flexible

  • Pretty secure

  • Some limitations


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