DVE over Ad Hoc Network

黃仁竑中正大學資工系 /通訊系

Outline

Introductionproblems

Addressing method Routing

unicast, multicast DVE architecture Conclusion

Main challenges

Characteristics of traditional DVEClient/Server ModelNetwork bandwidthDistributed interactionMessage typeScalabilityResource managementNetwork topology

Main Challenges (cont.)

Characteristics of Ad Hoc NetworkLack of infrastructureLow bandwidthSignals are easy to be obstructedMobilityLow reliabilityClient/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 NetworkRouting, mobility (dynamic re-addressing)

Building a networked virtual environment over P2P

Issues P2P over MANET

Overlay topologySelf-organizing, self-addressing

RoutingUnicast, multicast

MobilityFault tolerant

Overlay Topology

1.0

1.11.2

1.3

1.2.11.2.2

1.1.1

無線通訊範圍

行動裝置

Logical IP1.0

1.11.2

1.3

1.2.11.2.2

1.1.1

1.0

1.11.2

1.3

1.2.11.2.2

1.1.1

無線通訊範圍

行動裝置

Logical IP

Self-organizing

Self-addressing

Overlay construction:Join process

一節點一開機

等一段random的時間

廣播發出訊息檢查是有logical IP的節點(Nn)存在

無 自己成為root，logical IP為1.0，並將自己的MAC address當作該樹的ID。

有

廣播發出訊息檢查Nn所在的樹是否root存在

有

無

針對那些Nn發出要加入(requestto join)的訊息。

針對所有收到的回覆選擇selective IP長度最短的當作logical IP

收到那些Nn的回覆(response to join with selective logical IP)

沒收到那些Nn的回覆

向父節點發出回覆(response to join的ack)的訊息

確認取得logical IP，同時定期與父節點作聯繫的動作。

一節點一開機

等一段random的時間

廣播發出訊息檢查是有logical IP的節點(Nn)存在

無 自己成為root，logical IP為1.0，並將自己的MAC address當作該樹的ID。

有

廣播發出訊息檢查Nn所在的樹是否root存在

有

無

針對那些Nn發出要加入(requestto join)的訊息。

針對所有收到的回覆選擇selective IP長度最短的當作logical IP

收到那些Nn的回覆(response to join with selective logical IP)

沒收到那些Nn的回覆

向父節點發出回覆(response to join的ack)的訊息

確認取得logical IP，同時定期與父節點作聯繫的動作。

Addressing Issue(2)

Example1:

1.0

Request to join

Reply to join with IP

Reply ack

1.01.0

1.01.0

1.1

(1) (2) (3) (4) (5)

Addressing Issue(3)

Example2:

1.0

1.1

1.0

1.1Request to join

1.0

1.1

Reply with IP

Reply with IP

1.0

1.1

Reply ack

1.0

1.1 1.2

(1) (2) (3) (4) (5)

Policy to choose a parent node

For low mobility environmentDefine a threshold of signal strengthChoose parent that has shortest logical IP

and stronger signal strength than the threshold

Logical IP changes slowlyLess maintenance overhead

Other Possible Policies

Most power capacity Strongest signal Lowest mobility

Routing

Default routingTraverse the tree up to the nearest common

ancestor and then down to the destination Enhancement: Cache

Take advantage of broadcast Cache two-hop away neighborsLongest 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

1.0

1.11.2

1.3

1.1.2 1.2.21.1.1

1.3.1

1.1.1.11.1.1.2 1.1.2.1

主動告知

1.0

1.11.2

1.3

1.1.2 1.2.21.1.1

1.3.1

1.1.1.11.1.1.2 1.1.2.1

主動告知

Longest Prefix Match

1.0

1.11.2

1.3

1.1.2 1.2.21.1.1

1.3.1

1.1.1.21.1.1.1

1.1.2.1

1.0

1.11.2

1.3

1.1.2 1.2.21.1.1

1.3.1

1.1.1.21.1.1.1

1.1.2.1

Routing Combine with Routing Cache

1.0

1.11.2

1.3

1.1.2 1.2.21.1.1

1.3.1

1.1.1.1.1

1.1.2.1.1

1.1.2.11.1.1.21.1.1.1

1.0

1.11.2

1.3

1.1.2 1.2.21.1.1

1.3.1

1.1.1.1.1

1.1.2.1.1

1.1.2.11.1.1.21.1.1.1

Mobility

Nodes may select a new node as its parent:Signal strength is weaker than some thresholdSignal range can’t reach its original parent

Re-Addressing (cont.)

AB

Release IP of node PP

Request to joinA

B

Release IP of node PP

Request to join

發出加入的訊息(request to join)給父節點。

重新執行找logical address的程序，如先前所提到addressing的程序。

沒收到父節點的回覆(response to join)

檢查該父節點的logical IP長度是否有比原來的父節點短。

無

向該父節點發出要求新logicalIP的訊息(request to join)。

有

取得新的logical IP

沒收到該父節點的回覆(response to join)

收到該父節點回覆的logical IP(response to join)

發出父節點回覆(response tojoin)的ack給新的父節點

向原來的父節點作IP release的動作

向底下的子節點通知父節點IPaddress已經改變

開始與新父節點作定期註冊的動作

聽到其他父節點所發出的回應response to join

有收到父節點的回覆(response to join)

發出加入的訊息(request to join)給父節點。

重新執行找logical address的程序，如先前所提到addressing的程序。

沒收到父節點的回覆(response to join)

檢查該父節點的logical IP長度是否有比原來的父節點短。

無

向該父節點發出要求新logicalIP的訊息(request to join)。

有

取得新的logical IP

沒收到該父節點的回覆(response to join)

收到該父節點回覆的logical IP(response to join)

發出父節點回覆(response tojoin)的ack給新的父節點

向原來的父節點作IP release的動作

向底下的子節點通知父節點IPaddress已經改變

開始與新父節點作定期註冊的動作

聽到其他父節點所發出的回應response to join

有收到父節點的回覆(response to join)

Multicast

Members join Members leave Packet forwarding

Membership management

JoinTake advantage of the tree architecture

LeaveSimilar to join

P

Join

1

1.1 1.2

1.1.11.1.2

1.1.1.11.1.2.1

1.2.1

1.2.1.2

M

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 addressS: 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 serverDirect P2P message exchange (flood of mess

ages) 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

MulticastingFully distributed (no server)Scalable

AOIM (area of interest manager)Divide the virtual world into several cellsAssign 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

IO

render AOIM

Net

Control message from user

Message queue

Message queue

Message queue

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 entitiesOther 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?