DVE over Ad Hoc Network

1. DVE over Ad Hoc Network 黃仁竑 中正大學資工系/通訊系

2. Outline • Introduction • problems • Addressing method • Routing • unicast, multicast • DVE architecture • Conclusion

3. Main challenges • Characteristics of traditional DVE • Client/Server Model • Network bandwidth • Distributed interaction • Message type • Scalability • Resource management • Network topology

4. Main Challenges (cont.) • Characteristics of Ad Hoc Network • Lack of infrastructure • Low bandwidth • Signals are easy to be obstructed • Mobility • Low reliability • Client/Server architecture is not suitable

5. Project Statements • Study network virtual environment in Ad Hoc P2P networks • Approaches • Layered design • Similar to OSI/ISO 7 layer (or DVE over TCP over IP) • Separate DVE, P2P, Ad Hoc • Simulated scenario • Consider physical formation of Ad Hoc network • DVE is designed with physical Ad Hoc network in mind

6. Our Solutions and Goals • Constructing a P2P infrastructure on the Ad Hoc Network • Routing, mobility (dynamic re-addressing) • Building a networked virtual environment over P2P

7. Issues P2P over MANET • Overlay topology • Self-organizing, self-addressing • Routing • Unicast, multicast • Mobility • Fault tolerant

8. Overlay Topology Self-organizingSelf-addressing

9. Overlay construction:Join process

10. Addressing Issue(2) • Example1: 1.0 1.0 1.0 1.0 1.0 Reply to join with IP Request to join 1.1 Reply ack (4) (5) (1) (2) (3)

11. Addressing Issue(3) • Example2: 1.0 1.0 1.0 1.0 1.0 Reply with IP Reply ack 1.1 1.1 Request to join 1.1 1.1 1.1 1.2 Reply with IP (1) (2) (3) (4) (5)

12. Policy to choose a parent node • For low mobility environment • Define a threshold of signal strength • Choose parent that has shortest logical IP and stronger signal strength than the threshold • Logical IP changes slowly • Less maintenance overhead

13. Other Possible Policies • Most power capacity • Strongest signal • Lowest mobility

14. Routing • Default routing • Traverse the tree up to the nearest common ancestor and then down to the destination • Enhancement: Cache • Take advantage of broadcast • Cache two-hop away neighbors • Longest Prefix Match

15. Take advantage of broadcast • Node 1.1.1.2 is closer to 1.1.2.1 • Node 1.1.1.2 can detect that 1.1.1.1 is sending packets to 1.1.2.1 because of broadcasting

16. Longest Prefix Match

17. Routing Combine with Routing Cache

18. Mobility • Nodes may select a new node as its parent: • Signal strength is weaker than some threshold • Signal range can’t reach its original parent

19. Re-Addressing (cont.)

21. Multicast • Members join • Members leave • Packet forwarding

22. Membership management • Join • Take advantage of the tree architecture • Leave • Similar to join

23. Join 1 1.1 1.2 1.1.1 1.1.2 M 1.2.1 1.1.1.1 1.1.2.1 P 1.2.1.2

24. Rules of join • Requesting node P sends join message to its parent M • If M is already in the group, discard the message • Otherwise, the message will be forwarded to the parent of M up to the root

25. Forwarding • Packet format • <M,S,I> • M: multicast address • S: source address • I: intermediate address

26. Forward (cont.) • For some node A • Up • I is a child of A • I exactly matches the prefix of S • Down • I is the parent of A • S is not any descendant of A • Some descendants of A are members of M • If A is the root of the tree • If other branches have members of M, forward the packet

27. Issues of DVE in Ad Hoc Network • Unworkable solutions • Static server • Direct P2P message exchange (flood of messages) • Proposed solution • AOI+Multicast

28. AOI + Multicast • Entities (or avatar) only interested in receiving information from entities within AOI • Entities send messages to or receive them from their AOIs, corresponding to the region in which they are acting • Map each region (cell) into a multicast group

29. DVE software architecture • Multicasting • Fully distributed (no server) • Scalable • AOIM (area of interest manager) • Divide the virtual world into several cells • Assign distinct multicast channels to each cell

30. AOIM • Entities send messages to AOI (its cell and neighbor cells) via multicast channels • Entities listen to the multicast channel of its cell only • No centralized servers are needed

31. DVE software architecture Control message from user IO Message queue render AOIM Message queue Message queue Net

32. Leader of the cell • Leader maintains status of entities in the cell • When a new entity enters the cell, it requests information of other entities from the leader • The state of the new joined cell can be initialized

33. Election of cell leader • An entity enter a new cell • It sends a message to find the leader • If there is no response, it becomes the leader • When an entity leave a cell • It sends a message to tell other entities • Other entities then send their MAC address to the cell, and the entity with largest MAC address will be the new leader

34. Conclusion • P2P over MANET • Tree structured overlay topology • Self-addressing, self-organizing • Unicast and multicast routing • DVE • Multicast + AOI • What can be discussed in the future? • Connectivity, fast mobility • Commercial products?