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DVE over Ad Hoc Network. 黃仁竑 中正大學資工系 / 通訊系. Outline. Introduction problems Addressing method Routing unicast, multicast DVE architecture Conclusion. Main challenges. Characteristics of traditional DVE Client/Server Model Network bandwidth Distributed interaction Message type

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DVE over Ad Hoc Network

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DVE over Ad Hoc Network

黃仁竑

中正大學資工系/通訊系


Outline

  • Introduction

    • problems

  • Addressing method

  • Routing

    • unicast, multicast

  • DVE architecture

  • Conclusion


Main challenges

  • Characteristics of traditional DVE

    • Client/Server Model

    • Network bandwidth

    • Distributed interaction

    • Message type

    • Scalability

    • Resource management

    • Network topology


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


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


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


Issues P2P over MANET

  • Overlay topology

    • Self-organizing, self-addressing

  • Routing

    • Unicast, multicast

  • Mobility

    • Fault tolerant


Overlay Topology

Self-organizingSelf-addressing


Overlay construction:Join process


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)


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)


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


Other Possible Policies

  • Most power capacity

  • Strongest signal

  • Lowest mobility


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


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


Longest Prefix Match


Routing Combine with Routing Cache


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


Re-Addressing (cont.)


Multicast

  • Members join

  • Members leave

  • Packet forwarding


Membership management

  • Join

    • Take advantage of the tree architecture

  • Leave

    • Similar to join


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


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


Forwarding

  • Packet format

    • <M,S,I>

    • M: multicast address

    • S: source address

    • I: intermediate address


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


Issues of DVE in Ad Hoc Network

  • Unworkable solutions

    • Static server

    • Direct P2P message exchange (flood of messages)

  • Proposed solution

    • AOI+Multicast


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


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


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


DVE software architecture

Control message from user

IO

Message queue

render

AOIM

Message queue

Message queue

Net


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


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


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?


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