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Implementation of Label Switching for Distributed Control in Instrumentation System

1A.Irawan, 2N. Hazlina* Faculty of Electrical & Electronics Engineering,

Universiti Malaysia Pahang (UMP), Locked Bag 12, 25000 Kuantan, Pahang, Malaysia. 1addieirawan@ump.edu.my, 2hazlina@ump.edu.my

Abstract This article describes an implementation of label switching technique in data acquisition and control design for instrumentation control system. Multi-protocol Label switching (MPLS) and Basic Stamp II (BS-2) module are utilised in this system. Two layers of data labelling are defined for the system by considering the average distance and area of the system. This study has found that label switching concept that is being used for instrument unit data communication has the potential to be re-configured with the increment of number of instrumentation system and devices. Apart from that, limitation of processing unit memory and data storage could also affect the performance of data forwarding. However, these limitations has minimum effect on deploying scaling forwarding via label switching technique for instrumentation communication and control purposes. 1. Introduction

Data communication and networking for instrumentation system unit evolves rapidly due to the raising issues on implementation and application requirements. In this research, the focus is on introducing an alternative technique on data communication method for intermediate system of instrumentation units. In the internetworking or internet backbone area, Multi-protocol Label Switching (MPLS) IS introduced to solve the limitation of Internet Protocol (IP) address and improve the quality services on data forwarding. Therefore, this research initiates the implementation of MPLS-like technique and concept in instrumentation system area for process control.

This project develops several switchers and virtual instrument (control panel in computer) for control purposes. The main objective of the research is to

deploy and evaluate the potential of the label switching protocol for intermediate data communication for instrumentation unit (IU). 2. Instrumentation unit system design

In developing the instrumentation system unit, there are some important things that need to be focused; interface unit and control panel system development. In this research, three prototypes of switchers ARE developed; Instrument A (IA), Instrument B (IB), and Instrument C (IC), as in Figure 1.

Figure 1. Block diagram of Instrumentation Control Network System

This project has developed a graphical user

interface (GUI) of a suitable virtual instrument for the system using LabVIEW development tools. This development tools also prepare suitable data logging and interface tools which are important in computer control. In the first phase of this project, a virtual instrument to generate and receive labelled data is developed. This instrument is used for testing purposes. The hardware system (switchers and server) is developed using Basic Stamp II (BS-2) module. This

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micro-controller module allows user to do online monitoring on its internal data processing. Therefore, in the first phase of development, the project use BS-2 module as a main tools for data processing unit in each interface system unit of the IU members. BS-2 module provides 20MHz oscillation timer, 8 bit core and about 4000 instruction per-second execution speed.

Figure 2. Example of one of GUI system 3. Instrumentation Network Topology

The network topology of instrumentation control network system that needs to be tested is illustrated as Figure 3. IA, IB and IC are clustered as a group of sub-server or sub-switcher and internal IU which will be acted as transceivers system (Figure 3). The aim of this study is to do analysis on data distribution performances between control panel, server unit and instrumentation switcher.

Figure 3. Instrumentation Control System Network Model Topology

As mentioned in section I, label switching concept is used to set the data format for each distributed data

between control panel unit and IU members. Two particular labels have been defined and formatted for each navigated data which is Label 1 for device identification and Label 2 for unit identification (Figure 4). Therefore, 4 bits IS used for each label and others for information data.

Figure 4. Data Frame Format in the

Network System

For link set-up and data forwarding administration, IU system used the RS232 signalling procedure via RS232 transducer device as shown in Figure 5.

Figure 5. Data Signalling Level in Switching Unit in each Instrumentation Unit

First in first out (FIFO) procedure IS applied in

each receiving, transmitting and server system on each instrument unit. FIFO is used to hold and queued up the data which are arrived on intermediate network of network system. 4. Analysis of entire network performances

The project carries several analyses on the performance of data distribution for IU network system. The objective of the analysis is to evaluate the scaling performances of label switching which has been setup in each IU member including control panel system in personal computer (PC). The method of testing is illustrated as Figure 6.

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Figure 6. Network topology and setting for analysis purposes

Each IU members/systems which can be represented by a switch system will be tab for data collecting purposes accept PC. All data in PC will be collected in the programmed data logging system in named file. The test will consider the label switching performances which WAS programmed in each switcher in IU system.

In this development phase, the IU system is configured with 6 labels which are 10, 20, 30, 40, 50 and 60. The configuration of label is defined in Table 1.

Table 1: Label configurations for each IU

Flow Label Value Instrumentation System

ID 10 IA 20 IB

Transmit

30 IC 40 IA 50 IB

Receive

60 IC

0

10

20

30

40

50

60

PC Server IA IB IC

CFCPIU Systems

Num

ber o

f Fra

me

Label 10 Label 20 Label 30

Figure 7. Label scaling performances for each forwarded labelled frame for Transmit

flow cases (5 times repeating in each switcher)

0

10

20

30

40

50

60

PC Server IA IB IC Loss

CFCPIU Systems

Num

ber o

f Fra

me

Label 40 Label 50 Label 60

Figure 8. Label scaling performances for each forwarded labelled frame for Receive

flow cases (5 times looping in each switcher)

However, Figure 11 shows several losses occurred

in each forwarding flow especially for the number of looping/repeating in switching in each system is 5. Other issue has been raised in this testing progress. However, this problem arises when the number of looping/repeating in each switcher increase. Figure 11 shows a decrement in data losses up to 90% upon increasing the number of looping. However, increasing the number of looping/repeating will cost the growth of memory and processing unit usage. This will contribute latency on data forwarding either in Transmit flow or Receive flow.

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0

10

20

30

40

50

60

PC Server IA IB IC

CFCPIU Systems

Num

ber o

f Fra

me

Label 10 Label 20 Label 30

Figure 9. Label Scaling Performances for Each Forwarded Labelled Frame for

transmit Flow (10 times looping in each switcher)

0

10

20

30

40

50

60

PC Server IA IB IC

CFCPIU Systems

Num

ber o

f Fra

me

Label 40 Label 50 Label 60

Figure 10. Label scaling performances for each forwarded labelled frame for Receive flow (10 times looping in each switcher)

0

1

1

2

2

3

3

4

4

5

5

10 20 30 40 50 60

Label Identification Code

Perc

enta

ge o

f Los

ses

(%)

Looping 5 Looping 10

Figure 11. The Effect of increasing the number of repeating/looping in switching and forwarding data in each IU systems.

(Transmit and Receive flow)

5. Conclusion From scaling in switching point of view, the project

is success. However, on data forwarding reliability and quality, some problem occurred which is on limited storage and memory of BS-2. The continuity of this project will focus on replacing a compatible processing unit for each IU members with several new techniques on switching for efficiency and reliability purposes. All this modification and improvement will be done AS A preparation to the increasing number of devices that will be added in next development of carbon fibre process plant.

6.Acknowledgement

Special thanks to all researchers in Faculty of Electrical & Electronics Engineering, who are involved in this fundamental research. Also thanks to the management who support on the fund on publishing this article. 7.References [1] Stallings, W. (2001). Multi-protocol Label Switching (MPLS). The Internet Protocol Journal.Available at: http://www.cisco.com/warp/public. [2] Stalling, W. (2001). Data and Computer Communications, 7th ed.: Prentice-Hall International, Inc. [3] Irawan, A., Ahmad, R., B., (2002). Proposal of Modelling IP over WDM Network using OMNeT++. Proc. of the International on Robotics, Vision, Information and

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Signal Processing 2003 (IEEE Conference), Georgetown, Penang, Malaysia. pp. 209-215. [4] Irawan, A., Ahmad, R. B. (2003). IP/GMPLS overWDM Network: Implementation of WDM Tree Construction Protocol with QoS Support. Proc. of APCC 2003, the 9thAsia-Pasific Conference on Communications cons. with 6th Malaysia International Conference on Communications (MICC03), Georgetown, Penang, Malaysia. Vol. 2, pp. 756-758. [5] UK Patent 1 326 736, 1970. John Charles Joiner and Vernon Findlay. [6] UK Patent Application GB 2 071 702, 1981.Kazuhisa Saito, Hiroyasu Ogawa and Tetsuro Shegei [7] US Patent 4 234 398, 1980. Ryuichi Yamamoto and Ehime. [8] Travis, J., (2002). LabVIEW for Everyone. National Instruments Virtual Instrumentation Series. 2nd ed.: Prentice-Hall International, Inc.