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CIS 6930: Mobile Computing Mobile IP

CIS 6930: Mobile Computing Mobile IP. Sumi Helal Credit: majority of slides borrowed from one of Dave Johnson ’s talks,. 3. References. 2.1: C. Perkins and A. Myles, "Mobile IP," technical report.

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CIS 6930: Mobile Computing Mobile IP

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  1. CIS 6930: Mobile ComputingMobile IP Sumi Helal Credit: majority of slides borrowed from one of Dave Johnson’s talks, 3

  2. References • 2.1: C. Perkins and A. Myles, "Mobile IP," technical report. • 2.2: B. Lancki, A. Dixit, V. Gupta, "Mobile-IP: Supporting Transparent Host Migration on the Internet," Linux Journal, June 1996. • 2.3: D. Johnson and D. Maltz. "Protocols for Adaptive Wireless and Mobile Networkig", IEEE Personal Communication, 3(1), February 1996 • 2.4: C. Perkins and D. Johnson. "Mobility Support in IPv6," Proceedings of the Second Annual International Conference on Mobile Computing and Networking (MobiCom'96), November 1996. • 2.5: M. Baker, X. Zhao, S. Cheshire, J. Stone, Stanford University, "Supporting Mobility in MosquitoNet", USENIX Winter 1996

  3. Internet Protocol (IP) • Connectionless packet delivery • Unreliable delivery • IP host addresses consist of two parts • network id • host id • By design, host address is tied to its network

  4. Internet Protocol (IP) • Intermediate routers need only look at the network id • destination network responsible to get packet to right host • When a host moves to a new network, its IP address would have to change - packets to old address lost

  5. Mobile IP

  6. IETF Mobile IP Protocol(refer paper by Johnson & Maltz) • IETF = Internet Engineering Task Force: Standards development body for the Internet • Mobile IP allows a host to have a unique (location-independent) IP address. • Each host has a home agent on its home network. • The home agent forward IP packets when mobile host away from home.

  7. IETF Mobile IP Protocol(refer paper by Johnson & Maltz) • When away from home, mobile host has a care-of-address • care-of-address = address of foreign agent within the foreign subnet - the foreign agent delivers forwarded packets to mobile host • care-of-address may also be a temporary IP address on the foreign network

  8. Basic Architecture

  9. IETF Mobile IP • When moving, the host register with home agent - home agent always knows the host’s current care-of-address. • Correspondent host = Host that wants to send packets to the mobile host • Correspondent host sends packets to the host’s IP address, which are routed to the host’s home network.

  10. IETF Mobile IP • Correspondent host need not know that the destination is mobile. • Home agent encapsulates and tunnels packets to the mobile host’s care-of-address.

  11. Encapsulation and Tunneling • IP-in-IP encapsulation • Received IP packet is encapsulated in a new IP packet with a new header. In the new header: • Destination = care-of-address • Source = address of home agent • Protocol number = IP-in-IP

  12. Encapsulation and Tunneling • Encapsulation protocol at foreign agent removes added header, and transmits the packet to the mobile host over the local network interface

  13. IP-in-IP Encapsulation

  14. Minimal Encapsulation • Reduces the additional bytes added to header when encapsulating: 8 or 12 bytes are added. • Original source address need not be included in the tunnel header, if the original source is also the tunneling node

  15. Authentication • As host B can send “moving to new location” registration messages to host A’s home server, host B can pretend to be host A, and receive packets destined for host A. • To avoid this, all registration messages must be “authenticated”. • Protection against “replay” attacks must be provided.

  16. Route Optimizations • Binding updates : Correspondent host receives (from home agent) a binding update informing mobile host’s current care-of-address, when the home agent receives a packet from the correspondent host + the packet is forwarded • Correspondent host can cache the binding, and future packets can be tunneled directly to the care-of-address (without going via home agent) • Cache consistency: A cached binding becomes stale when the mobile host moves

  17. Route Optimization

  18. Route Optimizations • Binding warning: Used by old foreign agent, to request the home agent to send current binding to a correspondent host. • When a host moves: • Old foreign agent may cache a forwarding pointer to the new foreign agent: packets re-tunneled along the forwarding pointer + binding warning sent to home agent to update the correspondent with the new binding

  19. Route Optimization • Old foreign agent may not cache (or purge) the forwarding pointer: packets forwarded to home agent. Home agent tunnels it to current care-of-address + sends binding update to correspondent

  20. MosquitoNet • No foreign agent • Visiting mobile host is assigned a temporary IP address corresponding to the foreign subnet. • Packets are tunneled directly to the mobile host (without having to go through a foreign agent)

  21. MosquitoNet -- Advantages • Mobile hosts can visit networks that do not have home agents • Foreign agent is no more a single point of failure • Scalability: Foreign agent not needed on every network that a mobile may visit. Home agents only needed on networks with mobile clients • Simpler protocol: Only part of foreign agent functionality needed

  22. MosquitoNet -- Disadvantages • Mobile host needs to acquire a temporary IP on foreign subnet • Security: If a temporary IP address is re-assigned to another mobile to soon, the new mobile may receive packets intended for the previous mobile. • Packet loss: Foreign agents can forward packets destined for a mobile host that has moved to another foreign subnet. Without foreign agents, the packets will simply be lost. • Mobile host is more complex, as it must incorporate some of the functionality of a foreign agent.

  23. Other Protocols: CDPD • CDPD: Cellular Digital Packet Data • Similarity to Mobile IP: • triangular routing approach between mobile host and home and foreign agents • Differences: • User IP assigned by CDPD service provider • Uses prop. Tunneling not IP-in-IP • Not strictly above the data link layer

  24. Other Protocols: GPRS • GPRS: General Packet Radio Data GSN: GPRS Support Node MSC: Mobile Switching Center BTS: Base Transciever Station BSC: Base Station Controller

  25. Mobile IP vs. CDPD vs. GPRS • CDPD is slowing down (today Jan 1999) • Mobile IP is big in the US. IETF is behind it • US industry just started adapting Mobile IP (Sisco routers!). • Motorola’s iDEN network is Mobile IP based. • Microsoft’s position is not clear yet. Would they finally bundle it with Windows CE? • Europe: Initial copying of Mobile IP efforts. But now do have the advantages of wider interoperability (which is a UMTS requirement)

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