Multicast Based Micro-mobility: Design and Evaluation

1. Multicast Based Micro-mobility: Design and Evaluation Ganesha Bhaskara Network Design and Testing Lab Dept. Of EE, USC.

2. Outline • Problem Statement • Related Work • Architecture of M&M • Design of M&M • Mobility detection • Handoff • Performance comparison • Conclusion Ganesha Bhaskara

3. Micro-mobility Ganesha Bhaskara

4. Problem Statement • Better understanding of the challenges in Micro-mobility • Thorough evaluation of Multicast Based Micro-mobility Protocol (M&M) as a promising approach to micro-mobility through simulations, systematic (STRESS) modeling and testing • Compare architectural and performance issues of M&M with other micro-mobility protocols Ganesha Bhaskara

5. Framework of study • Architectural Issues • Routing mechanism • Route update mechanism • Mobility detection and handoff mechanisms • Performance Issues • Handoff delay and jitter • Control overhead • Robustness against packet loss Ganesha Bhaskara

6. Related Work

7. Approaches to micro-mobility • Hierarchical tunneling • Packets tunneled through tree / hierarchy of foreign agents • Packets are decapsulated and re-encapsulated at each hop • Example: Hierarchical Mobile IP • Mobile specific routing • Mobile specific routing table entries are created either by implicit or explicit signaling • Example: HAWAII, CIP, M&M Ganesha Bhaskara

8. Micro-mobility Protocols • Multicast based Micro-mobility Protocol (M&M) • Cellular IP (CIP) • Handoff Aware Wireless Access Internet Infrastructure (HAWAII) Ganesha Bhaskara

9. M&M • MN is assigned a domain wide unicast address – Regional Care of Address (RCoA) • All routers map the RCoA to its corresponding and unique Multicast Care of Address (MCoA) using algorithmic mapping • As MN moves from one sub-domain to another, it needs to join to its MCoA to receive packets Ganesha Bhaskara

10. Routing and Route Update • Multicast routing is used to route packets from border router to the mobile node • Packets destined to MN tunneled through multicast tree • Route update using Join / Prune messages Ganesha Bhaskara

11. M&M Ganesha Bhaskara

12. Routing Entry Creation Routers snoop on MN originated data to maintain reverse route Routing Cache Routers maintain (IP address of MH,incoming interface) Route-Update Maintain and refresh mapping Route update packet at regular interval if no data Cellular IP Routing Ganesha Bhaskara

13. Handoff in CIP • Hard handoff • High Packet loss • Simple • Semi-soft handoff • Reduced packet loss • Duplication and reordering of packets • MN receives packets from both old and new BS Ganesha Bhaskara

14. Issues With CIP • Two or more border routers in a domain • Packet to and from the MN may take different routes • Route establishment and update by snooping on data fails as reverse route is established from the BR through which packets exit rather than enter the domain • No mechanism like encapsulation / registration exists to forward to packets to the root of the tree (Rendezvous Point in PIM-SM) Ganesha Bhaskara

15. HAWAII (path setup schemes) • Cross over router – Router nearest to the MN that is in the intersection of two paths • Domain root router and the old BS • Old BS and the new BS Ganesha Bhaskara

16. HAWAII (path setup schemes) • Forwarding schemes – packets are forwarded from old BS first and then from the cross over router • MSF(Multiple Stream Forwarding) • SSF(Single Stream Forwarding) • Non-Forwarding schemes • UNF(Unicast Non-Forwarding) • MN can communicate with multiple BS at a time • MNF(Multicast Non-Forwarding) • MN cannot communicate with multiple BS at a time Ganesha Bhaskara

17. MSF • MN sends update message from new BS to Old BS (Old BS caches undeliverable packets) • Old BS updates routing table to forward cached and incoming packets to new BS and sends update message to next hop towards “new” BS • Update message diverts packets towards new BS on reaching the cross over router • Characteristics • General forwarding • {IP address  outgoing interface} • Packet reordering Ganesha Bhaskara

18. MSF Ganesha Bhaskara

19. HAWAII (MSF) Ganesha Bhaskara

20. MNF • MN sends route update to new BS • New BS sends route update hop by hop towards old BS • Cross over router multicasts data to both old and new BS for a short interval of time • Characteristics • Packet duplication and reordering Ganesha Bhaskara

21. MNF Ganesha Bhaskara

22. Related Work ….. Conclusions • Simulations of M&M, CIP and HAWAII have been done using • UDP and TCP traffic • Simple wireless model (loss less , zero delay) • Simple tree topologies • Conclusions • Micro-mobility schemes incur significantly less packet loss than Mobile IP • Secondary optimizations like MSF, SSF (as in HAWAII) or semi soft handoff (as in CIP) reduce packet loss even further Ganesha Bhaskara

23. Drawbacks • Lacks systematic study of factors affecting performance parameters • Simple wireless models can mask events that can cause protocols to fail • Simple tree topologies hides routing inefficiencies Ganesha Bhaskara

24. Contributions of This Study • Systematic study of factors affecting performance parameters using • Detailed wireless model (802.11) • Rich set of topologies (tree and mesh like) • Design guidelines for M&M (functional requirements for protocol correctness) • Performance evaluation using detailed packet level simulations Ganesha Bhaskara

25. Design Issues in M&M • Routing and Route update • Choice of multicast protocol • Effect of mechanisms of multicast protocol on routing efficiency • Mobility detection and Handoff mechanism • Algorithms for the same • Interaction of the above with mechanisms of multicast protocol Ganesha Bhaskara

26. Choice of Multicast Protocol • M&M represents a sparse membership scenario • Broadcast and prune protocols not suitable • Minimize resource usage • Our choice PIM-SM Ganesha Bhaskara

27. PIM-SM • Rendezvous Point (RP) • RP bootstrap and election algorithm • Placement of RP affects routing efficiency • Registration mechanism • Any BR can send packet to RP • No restriction on entry point of packets into a domain Ganesha Bhaskara

28. Rendezvous Point (RP) Placement Ganesha Bhaskara

29. Design of Mobility Detection and Handoff • Design for correctness • Protocol should setup routes to deliver packets to the MN • Protocol should be able to recover from loss of states / control packets to deliver data • Design for performance • Once the protocol satisfies the correctness conditions, the protocol can be tweaked for better performance • Low handoff delay • Low packet loss etc Ganesha Bhaskara

30. Mobility Detection and Handoff • Mobility Detection • Process by which Mobile Node (MN) finds out that it has moved into the coverage area of another Base Station (BS) and it needs to initiate handoff • Handoff • Process by which routes are updated such that packets are delivered to the new BS Ganesha Bhaskara

31. Mobility Detection Ganesha Bhaskara

32. Mobility Detection • BS assisted - using beacons • Beacon contains subnet / DR information • BS broadcasts beacons periodically • MN detects mobility when it receives new beacon • MN initiates handoff to the appropriate base station depending on the handoff algorithm • Transmission of beacons from adjacent BS should not be synchronized as they will collide in the overlapping region Ganesha Bhaskara

33. Issues in Mobility Detection • What triggers handoff ? • Power of received beacons • How many beacons to sample ? • If power information is not available • Handoff on first new beacon ? • Handoff after receiving “n” beacons from new BS ? • More handoff algorithms ……. beyond the scope of this study Ganesha Bhaskara

34. Issues in Mobility Detection • Why is it important ? • Sampling “n” beacons may take hundreds of milliseconds • MN could have crossed the overlap region before handoff is initiated • But link delays typically of the order of tens of millisecond • Faster the mobility detection, the better Ganesha Bhaskara

35. Handoff • Approaches to handoff • Network assisted handoff • MN assisted handoff • Network assisted handoff • MN sends ICMP packet to DR with its RCOA • DR maps the RCOA to MCOA using algorithmic mapping • DR sends a join to MCOA group • DR decapsulates unicast IP packet from the multicast packet Ganesha Bhaskara

36. Handoff • MN assisted handoff • MN needs to be aware that M&M scheme is being used • On detecting mobility, the MN sends a join to its multicast group • MN needs to decapsulate the unicast IP packet from the multicast packet Ganesha Bhaskara

37. Handoff in M&M • With overlap • Old and new BS simultaneously receive packets from the multicast tree (Bi-casting) • Bi-casting gives rise to • Negligible packet loss • Packet reordering and duplication • Bi-casting : natural extension of multicast • Equivalent to MNF in HAWAII and Semi soft handoff in CIP Ganesha Bhaskara

38. Bi-casting During Handoff RP Ganesha Bhaskara

39. Handoff Design for Bi-casting Scheme Ganesha Bhaskara

40. Forwarding Schemes and M&M • With no overlap • Mechanisms similar to forwarding schemes in HAWAII need to be incorporated • BS, on realizing that the packets can’t be delivered to the MN can buffer packets and multicast it to the CAR set • Forwarding schemes will require modification to multicast protocol and may not ensure zero packet loss Ganesha Bhaskara

41. Issues in Mobility Detection and Handoff • Mobility detection only through beacons • How to interpret loss of beacons ? • Out of range of BS • Lost due to collision • How many lost beacons indicates MN is out of range of BS ? • Answer to the above questions affects correctness of the protocol and hence performance Ganesha Bhaskara

42. STRESS • Used to iterate design of M&M especially mechanisms needed for • Mobility detection • Handoff • Used to generate scenarios for simulation • Check end cases Ganesha Bhaskara

43. Correctness Conditions • As long as a mobile node is in the range of a base station, there must exist an entry corresponding to the multicast group of the mobile node, at the DR on that LAN. • The absence of forwarder/designated router on the LAN will lead to packet loss • DR on the LAN should have an entry for the multicast group only if the MN is in range of the BS • Violation of this condition will lead to wasted bandwidth and increase in the number of multicast states Ganesha Bhaskara

44. STRESS Model of M&M • Protocol model • FSM of individual components • Global FSM • Topology model • Error model • Unacceptable states of the GFSM • Occurs due to violation of correctness conditions • STRESS is used to design for correctness rather than performance Ganesha Bhaskara

45. Protocol Model • FSM of Mobile Node including • Beacon receive timer • Solicit timer • FSM of DR and beacon transmit timer Ganesha Bhaskara

46. Topology Model Ganesha Bhaskara

47. Error Model • Black holes: When the mobile node moves from a base station in one sub-domain to another base station in another sub domain, packet loss may occur during handoff. Sustained loss of packets causes black holes Ganesha Bhaskara

48. Outcome of STRESS Study • Functionality requirements • MN should be able to recognize loss of beacons and take steps to recover from it • MN should ensure that the DR on the LAN knows its presence as long as it is in the range of the BS on that LAN • MN should be able to handoff to the best BS • Violation of this condition will lead to increased number of handoffs and hence degraded performance Ganesha Bhaskara

49. Beacon Receive Timer Ganesha Bhaskara

50. Recovery From Beacon Loss Ganesha Bhaskara