Transcript NPSNET: A NETWORK SOFTWARE ARCHITECTURE FOR LARGE SCALE VIRTUAL ENVIRONMENT Present by Zhang Weihui StudentID: 4070557 2015/11/7

NPSNET: A NETWORK SOFTWARE
ARCHITECTURE FOR LARGE SCALE
VIRTUAL ENVIRONMENT
Present by Zhang Weihui
StudentID: 4070557
2015/11/7
BRIEF INTRODUCTION

Motivation

Challenges

Software Tested for Solutions
Distributed Interactive Simulation Protocol
IP Multicast: Network Group Communication
Heterogeneous Parallelism
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Taxonomy

Communication
- Available network bandwidth determines the size and
richness of a VR
- Latency controls the interactive and dynamic nature of
the virtual environment

Views
- Synchronous
view
- Asynchronous view

Data
- Homogeneous world database
- Client-server

model
Processes
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Evolution of NPSNET Networking

History of NPSNET
- Its previous version and related application
protocol
- NPSNET-IV

SIMNET
- A brief introduction of SIMNET
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DIS PROTOCOL

Definition of DIS
-
DIS, which adopts the concordant configuration, standard,
protocol and database through the LAN or WAN, can establish an
interconnection between simulation and simulation program that
is distributed at different location.

Quality of Technique
Interoperability: Standard Database Structure, TCP/IP
Scalability: Dead Reckoning Method
Time-Space Coherence: Time and Space
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DIS PROTOCOL

PDU (Protocol Data Units)
The core of DIS protocol
IEEE 1278 defined 27 different PDUs
Only four of these are for entity interaction
Entity State, Fire, Detonation and Collision
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DIS PROTOCOL

Simulation Philosophy
Player: Each object is controlled on its own host
workstation by a software
Ghost: A version of player is dynamically modeled as an
object on every other workstation
Only four of these are for entity interaction
Dead-reckoning Algorithm
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Synchronization of Networking Game
 Two problems
Broadcast to who and what
Networking latency
 The specification of problem two
Sends instruction
Player A
Server
Player B
T0
T1
T2
A and B have a discrepancy of T2 – T1
Solution: (P4-P1)/T(P4-P3)
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Dead-Reckoning Algorithm
Predetermined error threshold
Definition
Methods
1： Target= Origin + S * (Tb – Ta)
2： Target= Origin + S * (Tb – Ta) + 1/2 * A * T
T = Dest( TargetB – OriginB ) / Speed
_TargetB = NewPDU.Speed * T
_S = Dest( _TargetB – OriginB ) / T
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Multicast

One to One Model
-
Multicast Group
Multicast Router
-
Having same bandwidth within one subnet when multicasting

IP Multicast: how to multicast
Five classes of IP address: Class D, Start bit ‘1110’
Range is 224.0.0.0 ~ 239.255.255.255
Class D IP Packet and IP Packet
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MBONE PROTOCOL

Brief introduction of MBone
-
The first formal tryout of MBone happened at 1992

MBone: the concept of networking transmission
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MBone

MBone Communication Protocol
-
UDP: that is adopted at transport layer
RTP: that is adopted at application layer
-
IGMP: that is adopted at network layer

The Architecture of MBone
1. Island
2. Mrouter (Multicast routing daemon)
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Three functions of mrouted
- Decide the routing path
- Copy packet
- Multicast packet switch
3. Tunnel (Two parameters)
- Metric: used to decide which routing path
- Threshold: limit the range of spread of multicast packet

The Operational Principle of MBone
1. Send out a Multicast IP packet from one host of Island
2. Execute mrouted to receive this packet
3. Repack the packet to unicast and send out
4. Revert the packet received to multicast packet
5. Receiving these IP multicast packet in different Island host
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ATM

Definition
-
ATM: This is the international standard for cell rely in which
multiple service types (such as voice, video, or data) are conveyed
in fixed-length (53 bytes) cells. Fixed-length cells allow cell
processing to occur in hardware, thereby reducing transit delays.
ATM is designed to take advantage of high-speed transmission
media.
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Heterogeneous Parallelism

Advantages
 Disadvantages
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Conclusion
The importance of distributed virtual environments continuing to
grow within the next several years. Government organizations
have recognized this through programs such as CATT, a
distributed 3D simulator for training tank crews and units and so
on.
Commercial interest is also keen. Some companies are pursuing
distributed VR for multi-player games.
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Thank You
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