Mobility and Multicast Protocol Design and Analysis

1. Mobility and MulticastProtocol 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. 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 2

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 3

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 4

5. Example S’ S HA R1 R2 R3 R4 R5 r1 r3 r4 r2 5

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 6

7. Example S’ S R6 R1 R7 R2 R3 R4 R5 r1 r3 r4 r2 7

8. Example S’ S S R6 R1 R1 R7 R2 R3 R4 R5 r1 r3 r4 r2 8

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 9

10. Data delivery in HBH MFT S H1 U Unicast Node U MFT H2 HBH Branching Node H2 H3 H1 MFT – Multicast Forwarding Table MFT MFT H2 H3 r3 r4 r1 r2 U r1 r3 r4 r2 10

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 11

12. Source mobility with M-HBH MFT MFT S’ S H1 H1 U U U MFT H2 H3 H1 MFT MFT H2 H3 r3 r4 r1 r2 U r1 r3 r4 r2 12

13. Receiver mobility with M-HBH MFT S H1 r3 MFT H1 U r1 r2 r2’ r3 r1 U Multicast Data U Join (r2/r2’) HA Home Agent U r2 r2 HA r2’ 13

14. Routing triangle First branching node F yS Last branching node L S’ S S xS zS L F z r x r y r 14

15. Theoretical models • 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 15

16. Theoretical models (2) • 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: 16

17. Example • Self-similar tree with k = 2, D = 3, and = 2 Level 0 Level 1 Level 2 Level 3 17

18. Simulation results (multicast tree shape) • Average length of Xs vs. Xr 18

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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 21

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 22

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 23

24. Questions? 24

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 25