1. Development of a Simulator for the HANARO Research Reactor (Communication Protocol)
H.S. Jung

2. Contents
Introduction
Network models
TCP
UDP
HLA

3. Introduction
A distributed simulation of a dynamic system consists of a group of components or subsystem simulations that communicate across a network during execution
All of the simulations run in parallel and pass data among themselves as needed over the network
Simulation
Non-real-time simulation
The rate of passage in the simulation may be arbitrary
Real-time simulation
The rate of passage in the simulation may be constrained to match the passage of real time

4. Introduction Benefits of distributed simulation
Non-real-time simulation
Speedup
Ability to connect multiple simulations
Real-time simulation
Requirements for communication
Correctness
Completeness
Speed

5. Network models ISO/OSI Network Model Layer 1 - Physical
Physical layer defines the cable or physical medium itself
Layer 2 - Data Link
Data Link layer defines the format of data on the network.
Ethernet addresses a host using a unique, 48-bit address called its Ethernet address or Media Access Control (MAC) address.
Layer 3 - Network
NFS uses Internetwork Protocol (IP) as its network layer interface. IP is responsible for routing, directing datagrams from one network to another.
Layer 4 - Transport
Transport layer subdivides user-buffer into network-buffer sized datagrams and enforces desired transmission control.
Layer 5 - Session
The session protocol defines the format of the data sent over the connections. The NFS uses the Remote Procedure Call (RPC) for its session protocol. RPC may be built on either TCP or UDP. Login sessions uses TCP whereas NFS and broadcast use UDP.
Layer 6 - Presentation
External Data Representation (XDR) sits at the presentation level. It converts local representation of data to its canonical form and vice versa. The canonical uses a standard byte ordering and structure packing convention, independent of the host.
Layer 7 - Application
Provides network services to the end-users. Mail, ftp, telnet, DNS, NIS, NFS are examples of network applications

6. Network models TCP/IP Network Model Layer 1 - Link Layer 2 - Network
This layer defines the network hardware and device drivers.
Layer 2 - Network
This layer is used for basic communication, addressing and routing. TCP/IP uses IP and ICMP protocols at the network layer.
Layer 3 - Transport
Handles communication among programs on a network. TCP and UDP falls within this layer.
Layer 4 - Application
End-user applications reside at this layer. Commonly used applications include NFS, DNS, Web, rlogin, talk, and ftp

7. Network models

8. TCP/IP Transmission Control Protocol/Internet Protocol
A family of communication protocols
High-level networking
Web
FTP
Remote login
Low-level networking
Transmission of packets of data between applications on the computers within networks

9. TCP/IP Architecture Application Application Transport Internetwork
Communicates with the transport layer
Transport
Deliver data to application
Error detection and retransmission
Internetwork
Deliver data to the correct computer IP
Network technology
A networking hardware
Application
Internetwork
Network technology
Transport

10. Encapsulation of Data

11. Communication with TCP/IP

12. Transport Protocols Two primary protocols Reliability of the protocols
TCP (Transmission Control Protocol)
Point-to-point communication
UDP (User Datagram Protocol)
Multicast communication
Reliability of the protocols
Error-free delivery
Assured delivery
Delivery in the same sequence the data was sent
No duplication of delivered data

13. TCP Connection-oriented protocol Stream-based Point-to-point
Similar to telephone
Reliable protocol
Stream-based
Data is a continuous stream of bytes
Ordering of data
Point-to-point
Complexity
Traffic
Large latency and small jitter
Use for non-real-time simulation

14. UDP Connectionless protocol Datagram-based Multicast
Similar to mailbox
Not reliable
Datagram-based
Data is a separate entity
No ordering
Multicast
Simplicity
No traffic
Small latency and large jitter
Use for real-time simulation

15. Effects of latency Latency degrades the overall performances
Use extrapolation to minimize the effects
Design data packet : for moving body
P(t)
V(t)
Timestamp
Estimation
P(t)’=p(t) + (ta-tt)V(t)
V(t)’=v(t) + [(ta-tt)/(tt-tp)] [v(tt) - v(tp)]

16. Lost Packets in UDP Monitoring variables Commands Not critical
Updated at next time
Commands
Critical
Use acknowledge method

17. Application in the simulator
Use UDP between simulator and instructor station
Data socket server
Multicast to the domain of user group
Data socket client
Connect with IP of the server in the user group domain
Use command acknowledge
Checks the response and retransmits if no acknowledge is received

18. HLA HLA (High Level Architecture)
A standard for communication among a group of cooperating simulations ( IEEE 1516)
A software architecture for creating computer simulations out of component simulations. The HLA provides a general framework within which simulation developers can structure and describe their simulation applications
Developed by DoD

19. HLA HLA Rules Interface Specification Object Model Template (OMT)
Ensure proper interaction of federates in a federation
Describe the responsibilities of federates and federations
Interface Specification
Defines Runtime Infrastructure (RTI) services and interfaces
Identifies “callback” functions each federate must provide
Object Model Template (OMT)
Prescribes the format and syntax for recording information
Establishes the format of key models
Federation Object Model (FOM)
Simulation Object Model (SOM)
Management Object Model (MOM)

20. References Jim Ledin, Simulation Engineering, CMP books,2001
IEEE Std , IEEE Standard for Modeling and Simulation (M&S) High Level Architecture (HLA) - Framework and Rules