1. Mobility and Multicast Protocol Design and Analysis Rolland Vida, Luis Costa, Serge Fdida Laboratoire d’Informatique de Paris 6 – LIP6 Université Pierre et Marie Curie, Paris ISCIS XVII, October 28-30, Orlando, FL

2. ISCIS XVII, Orlando, FL 2 Outline The mobility problem in a multicast group Traditional solutions Bi-directional tunneling Remote subscription Reducing routing triangles in M-HBH Performance analysis Theoretical models Simulation results Conclusion

3. ISCIS XVII, Orlando, FL 3 The problem More and more emerging mobile devices Mobility handling became an important service requirement Consider the following: 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. ISCIS XVII, Orlando, FL 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

5. ISCIS XVII, Orlando, FL 5 Example R1R1 R5R5 R4R4 R2R2 R3R3 S r4r4 r3r3 r2r2 r1r1 S’ HA

6. ISCIS XVII, Orlando, FL 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. ISCIS XVII, Orlando, FL 7 Example R1R1 R5R5 R4R4 R2R2 R3R3 S r4r4 r3r3 r2r2 r1r1 S’ R6R6 R7R7

8. ISCIS XVII, Orlando, FL 8 Example R1R1 R5R5 R4R4 R2R2 R3R3 S r4r4 r3r3 r2r2 r1r1 S’ R6R6 R7R7 R1R1 S

9. ISCIS XVII, Orlando, FL 9 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

10. ISCIS XVII, Orlando, FL 10 Data delivery in HBH U U H3H3 H1H1 H2H2 S r4r4 r3r3 r2r2 r1r1 r4r4 r3r3 H3H3 H2H2 H1H1 r2r2 r1r1 MFT U H2H2 Unicast Node HBH Branching Node MFT – Multicast Forwarding Table

11. ISCIS XVII, Orlando, FL 11 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

12. ISCIS XVII, Orlando, FL 12 Source mobility with M-HBH U U H3H3 H1H1 H2H2 S r4r4 r3r3 r2r2 r1r1 r4r4 r3r3 H3H3 H2H2 H1H1 r2r2 r1r1 MFT S’ U U H1H1 MFT

13. ISCIS XVII, Orlando, FL 13 Receiver mobility with M-HBH H1H1 U U S r3r3 r 2’ r2r2 r1r1 r3r3 H1H1 MFT U U r1r1 r2r2 r 2’ Join (r 2 /r 2’ ) Multicast Data HA Home Agent r2r2

14. ISCIS XVII, Orlando, FL 14 Routing triangle SS’ F xSxS ySyS zSzS S L z r y r x r F First branching node L Last branching node

15. ISCIS XVII, Orlando, FL 15 Perfect K-ary tree of depth D Receivers randomly placed on leaves is obtained as a weighted average: where is the probability of the first branching node being hops away from the source Theoretical models

16. ISCIS XVII, Orlando, FL 16 Self-similar k-ary tree of depth D Between a node at level and a node at level there are concatenated links, and where is the similarity factor Then, is obtained as follows: Theoretical models (2)

17. ISCIS XVII, Orlando, FL 17 Example Level 3 Level 2 Level 1 Level 0 Self-similar tree with k = 2, D = 3, and = 2

18. ISCIS XVII, Orlando, FL 18 Simulation results (multicast tree shape) Average length of Xs vs. Xr

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21. ISCIS XVII, Orlando, FL 21 Simulation results (source mobility) A) Average delivery delay M-HBH vs. BT vs. RS B) Relative gains in average delivery delay proportional to the average length of Xs

22. ISCIS XVII, Orlando, FL 22 Simulation results (receiver mobility) A) Average delivery delay M-HBH vs. BT vs. RS B) Relative gains in average delivery delay proportional to the average length of Xr

23. ISCIS XVII, Orlando, FL 23 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

24. ISCIS XVII, Orlando, FL 24 Questions?

25. ISCIS XVII, Orlando, FL 25 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