1. 1 References –Mobile Computing by T. Imielinski and H. F. Korth, Kluwer, 1996. –Andrew T. Campbell, Javier Gomez, and et al., Design, Implementation, and Evaluation of Cellular IP, IEEE Personal Comm., pp. 42 - 49, Aug. 2000. –Henning Schulzrinne and Jonathan Rosenberg, The Session Initiation Protocols, IEEE Comm., pp. 134-141, Oct. 2000. –Hong Liu and Petros Mouchtaris, Voice over IP Signaling, pp. 142-148, Oct. 2000. –IPng and the TCP/IP Protocols by Stephen A. Thomas, Wiley, 1996. –Yoram Bernet, The Complementary Roles of RSVP and Differentiated Services in the Full-Service QoS Network, IEEE Comm., pp. 154 - 162, Feb., 2000.

2. 2 Mobile IP Myungchul Kim mckim@icu.ac.kr

3. 3 –Ch. 1 and 2 of Mobile IP Design Principles and Practices by Charles E. Perkins, Addison-Wesley, 1998. –communicating via laptop should be as natural as using a telephone -> seamless roaming –IP address (physical location) routing prefix (often determined by the netmask) host number –two conflicting requirements for a changeable network address (for routability) and a stable network address (for identification purposes for transport protocols, notably TCP) associations between the two network addresses involved -> nomadic (or mobile) computing

4. 4 –the problem with mobility: mobile computers move from one IP subnet to another, but have the wrong subnet prefix for the destination subnet. –Mobile IP: one IP address is available for locating the mobile computer and another is available for identifying a communication endpoint on the mobile computer.

5. 5 –care-of address, home network, home address, readdressing (home address -> care-of address), inverse readdressing –the abstract functions to support mobility readdressing at the home network associating the home address and the care-of address of the mobile node delivering the datagram to the care-of address inverting the readdressing operation once the datagram arrives at the care-of address

6. 6 –IETF Mobile IP –where mobile networking fits? The mobility problem can be transformed into a routing problem (of network layer) in a natural way.

7. 7 –Mobile IP a modification to IP that allows nodes to continue to receive datagrams no matter where they happen to be attached to the Internet. Scalability –Functions of Mobile IP agent discovery (solicitation by mobile node) registration (directly with its home agent or through a foreign agent) tunneling –protocol tunneling to hide a mobile node’s home address from intervening routers between its home network and its current location

8. 8 –two ways to acquire a care-of address the care-of address is an IP address of the foreign agent: it allows many mobile nodes to share the same care-of address. A colocated care-of address is a care-of address acquired by the mobile node as a local IP address (through DHCP) –rough outline of the operation of the Mobile IP protocol 1. Mobility agents advertise their presence via agent advertisement messages. A mobility node may optionally solicit an agent advertisement message by using an agent solicitation message.

9. 9 2. A mobile node receives an agent advertisement and determines whether it is on its home network or a foreign network. 3. When the mobile node detects that it is located on its home network, it operates without mobility services. If returning to its home network from being registered elsewhere, the mobile node deregisters with its home agent through a variation of the normal registration process. 4. When a mobile node detects that it has moved to a foreign network, it obtains a care-of address on the foreign network. 5. The mobile node, operating away from home, then registers its new care-of address with its home agent through the exchange of a registration request and registration reply message. 6. Datagrams sent to the mobile node’s home address are intercepted by its home agent to the mobile node’s care-of address, received at the tunnel endpoint and finally delivered to the mobile node. 7. In the reverse direction, datagrams sent by the mobile node may be delivered to their destination using standard IP routing mechanisms, without necessarily passing through the home agent.

10. 10 –Charles E. Perkins, Mobile Networking through Mobile IP, IEEE Internet Computing, pp. 58 - 69, Jan. and Feb. 1998. Mobile IP –Discovering the care-of address –Registering the care-of address –Tunneling to the care-of address

11. 11 Discovering the Care-of Address –Router advertisement (RFC 1256) -> agent advertisement Allows for the detection of mobility agents Lists one or more available care-of addresses Informs the mobile nodes about special features provided by foreign agents, e.g., alternative encapsulation techniques Lets mobile nodes determine the network number and status of their links to the Internet, and Lets the mobile nodes know whether the agent is a home agent, a foreign agent, or both –Router solicitations (RFC 1256) -> agent solicitation

12. 12 Registering the Care-of address –When a home agent accepts the registrations request, it begins to associate the home address of the mobile node with the care- of address(next slide) –Registration lifetime –Binding: home address, care-of address, and registration lifetime –Each mobile node and home agent must share a security association and be able to use Message Digest 5 (RFC 1321) with 128-bit keys to create unforgeable digital signatures for registration requests. –Replay attack

13. 13

14. 14 –Two may ways to make the identification field unique Timestamp Pseudorandom number –The identification field for pending registration request –Automatic home agent discovery: broadcast IP address -> rejection to the mobile node (HA IP address) Tunneling to the Care-of Address –4: IP-within-IP –55: minimal encapsulation – next slide

15. 15

16. 16 Changes with IP version 6 –Mobility support in IPv6 A mobile node can configure its a care-if address by using Stateless Address Autoconfiguration and Neighbor Discovery in IPv6. Foreign agents are not required. IPv6-within-IPv6 tunneling is also specified. –Route optimization Packets delivery without assistance from the home agent –Security Strong authentication and encryption feature –Cost of performance –Internet-wide key management –Source routing Security Performance

17. 17 –In IPv6, key management between the mobile node and correspondent nodes is more likely to be available –Other features supported by IPv6 mobility Coexistence with Internet ingress filtering: many border routers discard packets coming from within the enterprise if the packets do not contain a source IP address configured for one of the enterprise’s internal networks. Smooth handoff

18. 18 Ongoing work and open questions –Routing inefficiencies Triangle routing Route optimization –Security issues Firewalls Such communications, originating from the mobile node, carry the mobile node’s home address, and would thus be blocked by the firewall. –Ingress filtering –User perceptions of reliability –Slow growth in the wireless LAN market

19. 19 –Competition from other protocols PPTP and L2TP based on PPP –Current development efforts Vertical handoffs between dissimilar media Ad-hoc networking