1. M-HBH Efficient Mobility Management in Multicast Rolland Vida, Luis Costa, Serge Fdida Laboratoire d’Informatique de Paris 6 – LIP6 Université Pierre et Marie Curie, Paris NGC ‘02, October 23-25, Boston, MA

2. NGC ’02, Boston, MA 2 Outline The mobility problem in a multicast group Traditional solutions Bi-directional tunneling Remote subscription The original HBH protocol Mobility handling in M-HBH Performance analysis Conclusion

3. NGC ’02, Boston, MA 3 The problem More and more emerging mobile devices Mobility handling became an important service requirement The multicast service: a multicast group, identified by a multicast address G a source S that sends data to G a receiver r that listens to packets sent to G How to assure multicast data delivery if … the source S is mobile or the receiver r is mobile

4. NGC ’02, Boston, MA 4 Traditional solutions (1) Proposed by Mobile IP [Perkins, RFC 3220] Bi-directional tunneling (BT) tunnel between the home and the foreign location of the MN Source mobility: data is tunneled to the home network, and then retransmitted on the old tree Receiver mobility: data is delivered on the old tree, and then tunneled to the MN Drawbacks: triangular routing encapsulation/decapsulation of data tunnel convergence (receiver mobility)

5. NGC ’02, Boston, MA 5 Example R1R1 R5R5 R4R4 R2R2 R3R3 S r4r4 r3r3 r2r2 r1r1 S’ HA

6. NGC ’02, Boston, MA 6 Traditional solutions (2) Remote subscription (RS) reconfiguration of the multicast tree according to the new location of the MN Source mobility: receivers redirect their Join messages towards the new location of the source Receiver mobility: the MN joins the tree from its new location Drawbacks: Source mobility: the entire tree must be reconstructed reconstruction is costly, not efficient for a highly mobile source Receiver Mobility cost is lower, only a branch has to be added

7. NGC ’02, Boston, MA 7 Example R1R1 R5R5 R4R4 R2R2 R3R3 S r4r4 r3r3 r2r2 r1r1 S’ R6R6 R7R7

8. NGC ’02, Boston, MA 8 Example R1R1 R5R5 R4R4 R2R2 R3R3 S r4r4 r3r3 r2r2 r1r1 S’ R6R6 R7R7 R1R1 S

9. NGC ’02, Boston, MA 9 Hybrid solutions Switch between the two techniques, based on specific criteria Mobile Multicast Protocol (MoM) [Harrison et al., Mobicom ’97] Range-Based MoM [Lin et al., Infocom ’00] Hierarchical Multicast Architecture [Wang et al., ACM Mobile Networks and Applications, 2001]

10. NGC ’02, Boston, MA 10 HBH multicast In traditional multicast, the group is a single unit, identified by the multicast address Mobility of an individual member is hard to handle Keep the unit (tree) + tunnel Reconstruct the unit (tree) HBH – Hop-By-Hop Multicast Routing [Costa et al., Sigcomm ’01] Uses a recursive unicast addressing scheme to provide multicast Data is not sent to the group, but to the next branching node Nodes are handled as individuals, not as a group

11. NGC ’02, Boston, MA 11 Data delivery in HBH H1H1 H5H5 H4H4 H2H2 H3H3 S r4r4 r3r3 r2r2 r1r1 r4r4 r3r3 S H4H4 SH3H3 SH2H2 H2H2 S r2r2 r2r2 r1r1 S S MFT MCT H1H1 H2H2 Relay Node Branching Node MFT – Multicast Forwarding Table MCT – Multicast Control Table

12. NGC ’02, Boston, MA 12 The M-HBH protocol In HBH multicast, nodes are treated as individuals, not as a group Mobility is easier to handle Mobile Hop-By-Hop Multicast Routing Protocol Extension of HBH Handles both source and receiver mobility Mobile Node Multicast connectivity – M-HBH Unicast connectivity – Mobile IP

13. NGC ’02, Boston, MA 13 Source mobility with M-HBH H1H1 H5H5 H4H4 H2H2 H3H3 S r4r4 r3r3 r2r2 r1r1 r4r4 r3r3 H4H4 S/SH3H3 H2H2 H2H2 r2r2 r2r2 r1r1 MFT MCT S’ U1U1 U2U2 S/S H2H2 MFT S/S’ U Unicast Router

14. NGC ’02, Boston, MA 14 Receiver mobility with M-HBH H1H1 H2H2 U S r3r3 r 2’ r2r2 r1r1 r3r3 H1H1 S S MFT MCT H3H3 H4H4 r2r2 S r2r2 S MFT r1r1 r2r2 r 2 /r 2’ S MCT r3r3 Join (r 2 /r 2’ ) Multicast Data HA Home Agent r2r2

15. NGC ’02, Boston, MA 15 Advantages of M-HBH Reduces triangular routing Better delivery path No encapsulation, no tunneling Transparent handling of mobility Preserves the advantages of HBH Passes through unicast-only clouds Takes into account asymmetric routes, data is forwarded on direct shortest path Limits tree reconstruction …

16. NGC ’02, Boston, MA 16 The M-HBH tradeoff M-HBH represents a trade-off between: Shortest path delivery Tree reconstruction M-HBH shortcuts routing triangles, but… Passing through the first (or the last) branching node does not assure shortest path delivery Periodical tree reconfiguration can be considered Reconfiguration frequency is limited

17. NGC ’02, Boston, MA 17 Routing triangle SS’ F xSxS ySyS zSzS S L z r y r x r F First branching node L Last branching node

18. NGC ’02, Boston, MA 18 Performance analysis Mathematical models K-ary trees Self-similar trees Simulation Realistic Internet-like generated topology

19. NGC ’02, Boston, MA 19 Simulation results (multicast tree shape) Average length of Xs vs. Xr

20. NGC ’02, Boston, MA 20 Simulation results (source mobility) A) Average delivery delay M-HBH vs. BT vs. RS B) Relative gains in average delivery delay, for M-HBH over BT, proportional to the average length of Xs

21. NGC ’02, Boston, MA 21 Simulation results (receiver mobility) A) Average delivery delay M-HBH vs. BT vs. RS B) Relative gains in average delivery delay, for M-HBH over BT, proportional to the average length of Xr

22. NGC ’02, Boston, MA 22 Conclusion Traditional solutions have drawbacks: Triangular routing, encapsulation (BT) Frequent tree reconstruction (RS) M-HBH uses a recursive unicast addressing scheme Reduces routing triangles eliminates tunneling limits tree reconstruction Simple, transparent, incrementally deployable Simulations show important performance gains Further details and analysis: hhtp://www-rp.lip6.fr/~vida/mhbh_techrep.pdf

23. NGC ’02, Boston, MA 23 Questions?

24. NGC ’02, Boston, MA 24 Mobile multicast source Shared Multicast Tree (CBT, PIM-SM) S sends data in unicast to the core (RP) data is retransmitted on the shared tree if S moves in a new network, it still can send unicast packets to the core (RP). Data is delivered to receivers. Source-Specific Multicast Tree (PIM-SSM) the multicast tree is rooted in the home network of S S moves in a new network and obtains a new address (S’): Multicast packets sent by S’ are dropped if … no multicast router in the visited network no multicast routing state in the router