CSCI 6433 Internet Protocols Class 8

1. CSCI 6433Internet ProtocolsClass 8 David C. Roberts

2. Topics • Mobile IP • Virtual Private Networks

3. Mobile IP • IP was not designed with hand-held or book-sized mobile computers in mind • Mobile IP has its limitations in today’s world, where IP address is tied to network address which is geographic

4. Mobile IP Allows portable computers to move from one network to another. Hosts move from one network to another, not in the original design of IP! Either • Host address must change, or • Routers must send a host-specific route across the entire Internet

5. General Characteristics of Mobile IP • Transparency—mobility transparent to applications, transport layer protocols, routers not involved in the change. • Interoperability—mobile host can interoperate with stationery and mobile hosts using IPv4, and mobile IPv6 hosts can interoperate with stationary and mobile IPv6 hosts • Scalability—scales to large internets • Security—authentication for all messages • Macro mobility—focuses on long-duration moves, rather than roving as in a cellular phone system

6. Overview of Mobile IPv4 • Host can have primary and secondary address • Primary is obtained at “home” location, permanent and fixed • Secondary obtained after a move. Sent to agent (router) at home. • Agent intercepts datagrams, encapsulates in IP datagrams, sends to secondary address. • Mobile host deregisters when returning home, notifies agent of new address after another move

7. Mobile IPv4 Addressing • Home address—conventional IP address • Temporary address is called care-of address • Two forms of care-of address: • Co-located: mobile host does forwarding • Foreign: foreign agent (router) on network being visited assigns care-of address, handles forwarding

8. IPv4 Foreign Agent Discovery ICMP router discovery mechanism used to discover a foreign agent.

9. IPv4 Agent Registration

10. IPv6 Mobility • No use of foreign agent or care-of addresses. Instead, IPv6 mobile host uses co-located care-of address • Host can have a home address and co-located care-of address at once • IPv6 does not depend on link-layer forwarding • IPv6 routing expansion header makes forwarding more efficient than for IPv4 • IPv6 mobile host does not need foreign agent

11. IPv6 Datagram Transmission • IPv6 mobile host informs home agent before communicating with a destination • Host includes a mobility header in sent datagram • Destination can then communicate with home agent, find mobile’s current address, and send directly

12. Assessment of Mobile IP • Not really a success • VPN allows remote device to have home address and have full access to its home network • Retaining an IP address is less important than it was, due to dynamic IP address assignment • Too much overhead to handle rapid movement such as telephones

13. Summary • Mobile IP allows a computer to move from one network to another without changing its IP address • Mobile either obtains a co-located care-of address or discovers a foreign mobility agent and requests a care-of address. • Once registered, mobile can communicate with an arbitrary computer on the Internet. • Datagrams from mobile go directly to destination • Return datagrams go through mobile’s home agent

14. Private Networks VPN • Allow external connections • Keep internal datagrams private • Can build a private internet, not connected to the public Internet • Can build private network, but connect each site to the Internet also (hybrid network)

15. Virtual Private Network

16. Virtual Private Network

17. VPN Addressing

18. VPN with Private Addresses

19. Summary • VPN—less costly alternative to private connection between networks • Address gateways, NAT used to allow communication between networks in different address domains • NAT can provide access to the Internet to a host with a private IP address