ECE544: Communication Networks-II, Spring 2009

1. ECE544: Communication Networks-II, Spring 2009 H. Liu Lecture 10 (Mobility) Includes tutorial materials from D. Raychaudhuri, C. Perkins, D. Reininger

2. Today’s Lecture • Announcements: Final Exam • Mobile IP • Network Security

3. Announcements • Final: Monday, May 11, 8:00 PM-11:00 PM, Location: SEC 210 • OPEN BOOK: Only the textbook, Peterson & Davie, "Computer Networks: A Systems Approach“ plus 2 pages of notes are permitted. • Textbook Chapters 1 – 6, Chapter 8, and Lecture Slides (Chapters 1 and 2 are not the main focus of this final exam but are needed as background knowledge) • Calculator is permitted • Course Survey: end on Monday, May 4

4. Review • Ethernet switching, wireless LAN • MPLS basic, ATM • IP Routing (RIP, OSPF, BGP) • IP Addressing (Subnetting, CIDR, IPV6) • Mobile IP • End-to-End Protocols (UDP, TCP, RTP) • Congestion control and QoS (queuing disciplines, TCP congestion control, congestion avoidance, IntServ, DiffServ) • Network Security

5. Mobility in Cellular Networks

6. Cellular Concept of Mobility • Users have a home system but can register at visited systems to make and receive calls – Single Number Service • Users can roam among systems during a call and the call is handed-off without being dropped.

7. Home Location Register – Maintains current customer Location and service profile HLR AC Authentication Center – Authenticates users VLR Visitor Location Register- Maintains temporary information on Visiting users. Functional Elements Home System Visited System

8. 3) The VLR sends a registration message to the HLR. HLR/AC Old VLR VLR 2) VLR queries previous VLR for user’s (actually the user’s smart card) permanent ID. Visited System 1) Visited system detects handset, handset transmits temporary ID assigned by previous system. Handset GSM Registration

9. Mobile IP Networks

10. Name, Address, Routing • Name: is a location independent identifier of a host • Address: indicates where a given host is located. • Route: tells how to get to a destination

11. Mobility Problem: The Internet Viewpoint • Internet addresses are assigned in a topologically significant manner. • A mobile host must be assigned a new address when it moves. • Change host address  connection breaks. • Retain host address  routing fails. • Host address must be preserved regardless of its location.

12. Constraints • Inter-operability with TCP/IP protocol suite. • Existing networking apps should run unmodified on mobile hosts. • System should provide Internet-wide mobility. • No modification on existing routing infrastructure should be required. • Solution should be independent of wireless hardware technology. • Solution should have good scaling properties.

13. IP’s subnet model vs. Mobility • Terminals move from one IP subnet to another, but have the wrong “subnet prefix” for the destination subnet. • Solution: two-tier IP addressing • The mobile keeps its static IP address, but borrows the service of a “care-of-address” on whatever IP subnet it happens to be visiting. • A “care-of-address”, offered by a mobility agent, can be shared by visiting mobiles.

14. Basic Mobile IP • How does it work? • Agent discovery: advertisement/solicitation • MH registration • Use of Care-of-Address (COA) • Proxy ARP (Address Resolution Protocol) • Packet tunneling • Triangle routing

15. Key components Home Address: MH’s permanent IP address, network ID of this address identifies the mobile’s home network. MH Home Agent (HA): a router attached to the MH’s home network maintains current location information for the MH is responsible for forwarding packets destined for the MH when MH is away from home. HA HN Home Network: the network identified with a mobile node R1 R3 Route Optimization FN FN R2 MH CH Foreign Network: a network, other than MA’s home network, that MH is currently attached to. Care-of-address: the IP address of the foreign agent Mobile Host: a host capable of changing its point of attachment to the Internet FA Corresponding Host: a host or router communicationg with a mobile node. Foreign Agent (FA) a router in the foreign network that the MH is visiting provides routing services to the MH while registred de-tunnels datagram to MH may serve as default router for outgoing packet from MH

16. Route Optimization • Provides a means for nodes to • cache the bindings of a mobile node • tunnel their own datagrams directly to the care-of-address • bypass mobile node’s home agent during datagram delivery • Allow datagrams sent based on an out-of-date cached binding, to be forwarded to the mobile node’s new care-of-address.

17. Terminology • Binding cache • a cache of mobility bindings of mobile nodes • maintained by CH for use in tunneling datagrams to those mobile nodes. • Binding update • a message indicating a mobile node’s current mobility binding and its care-of-address. • Registration lifetime • the time duration for which a binding is valid.

18. Route Optimization • Key features • Binding cache update • Smooth handoffs between foreign agents • New messages • binding update • binding request • binding warning • binding ack

19. Binding Cache Creation/Update • At CH, if no binding cache exists • datagrams will be routed to MH via basic mobile IP routing • home agent should then send a Binding Update message to the original source node • CH will then create a binding cache for the MH • At an FA, if MH has moved to a new FA and the old FA still receives tunneled datagrams • old FA send Binding Warning message to HA to advise the change.

20. Foreign Agent Smooth Handoff • As part of registration procedure, the mobile host may request its new FA to notify its previous FA on its behalf • a Previous Foreign Agent Notification extension is included in the Registration Request message • The new FA builds a Binding Update message and transmits it to the mobile node’s previous FA as part of registration, requesting an ACK from the previous FA • Security association between old FA and MH are used for authentication of the binding update message.

21. Mobile IP in IPv6 • Mobile IPv6 shares many features with Mobile IPv4, • but: • Mobility protocol fully integrated into IPv6 • Provides many improvements over Mobile IPv4. • No Foreign Agent: all care-of-address are collocated • Intrinsic "Route Optimization" mechanism • Automatic procedures for acquiring CoA: stateless addr autoconfig, DHCP (stateful)

22. Mobile IPv6 • MH uses Binding Update and Binding Ack to inform its HA or a CH of its new care-of-address • HA and CH can send Binding Request to MH to request Binding Update • Binding Update, Binding Ack, and Binding Request uses IPv6 optional header (Destination Option Header) and can be piggybacked with data payload • Use of IPv6 Routing Header option for avoiding triangular routing • Destination addr in IPv6 header = MH care-of address • “type 0” routing header: addr = MH home address • HA possibly tunnels first few IP packets using IPv6-in-IPv6 encapsulation • MH sends Binding Update to CH

23. Mobile IPv4 Advantages: a lot of mobile IPv4 implementations are available on different OS Limitations too small address space. lack of support for Integrated Route Optimization Control messages not included inside IPv4 data packet header Mobile IPV6 Advantages Address space (128 bit) Route optimization Optional header structure to support mobility QoS treatment Limitations IPV6 is not popular yet Mobile IPv4 vs Mobile IPv6