127

6. EXPERIMENTAL RESULT ANALYSIS

6.1 INTRODUCTION

Replica Management in the proposed DUDDI system is all about proposing

a proper methodology to maintain consistency in Services information across all

nodes of the DUDDI system, wherever the replicas are placed. Chapter 3 elaborated

the experimentation methodology wherein the Distributed UDDI Architecture has

been well defined along with its components. Based on the proposed Distributed

UDDI Architecture a detailed experimentation framework has also been proposed

in Chapter 3. Various challenging factors that are to be considered for replica

placement and replica consistency have been identified. The performance attribute

layer of the proposed experimentation framework listed out a set of performance

attributes to be considered for evaluating the effectiveness of the proposed

methodology for replica placement and replica consistency. Based on the

discussions, the proposed methodology is to be evaluated with respect to the

number of message passes, the message density, the processing and the success

ratio. This evaluation is to be carried out between a Traditional P2P based DUDDI

system and the DST structured P2P DUDDI system. Also, it has been proposed to

optimize the DST structured P2P DUDDI system using Ant Colony Optimization.

There is a separate set of evaluation to be carried out between the DST structured

P2P DUDDI and the ACO optimized DST structured P2P DUDDI. The evaluation

has been proposed to be Service Consistency based, Availability based and Cost

based assessments.

Chapter 4 elaborated the way how the proposed Distributed UDDI system

has been modeled and simulated in OMNET++. Using OMNET++, a P2P DUDDI,

DST structured P2P DUDDI and ACO optimized DST structured P2P DUDDI

128

system have been simulated. Based on the identified assessment criteria for the

given set of performance attributes and using the simulated DUDDI environments

as the test bed, experimentation was conducted as discussed in Chapter 5.

By using the experimental setup and based on the identified attributes and

assessment methodologies, the simulated environment has been used as the test bed

for conducting set of experimental simulations and the results are analyzed in this

Chapter. Chapter 6.2 is devoted for a theoretical analysis which will set a base to

analyze and realize the performance of the results of the experimental simulation.

6.2 THEORETICAL ANALYSIS

The perceived Replica Management in the proposed P2P based DUDDI

system is to be performed in a way that a DUDDI node holding the latest replica of

the Service information acts as the server for all the purposes of the replica update

and Read requests. On receiving the Read requests from other nodes, latest replica

is to be communicated to the requesting node of the DUDDI system. All Write

operations assume higher priority over Read operations in the proposed Replica

Management Methodology. This ensures that the Read requests are always serviced

with the latest replicas. Also, it has been one of the prime objectives of this

research, from the communication perspective, that the proposed DUDDI system

should be able to deliver the requested replica in a highly reduced number message

passes across the nodes of the DUDDI system. The following Theoretical analysis

creates the base for this objective.

In the P2P based DUDDI System, a Read operation is defined as the process

of getting the latest version of the Service information or its replica from a SRL

node. On the other hand, the Write operation is defined as the process of publishing

a new Service information or updating the latest version of the Service information

129

on a node and updating the Service information and version. In DST structured P2P

based DUDDI System, Read operation is the process of getting the Service

information or its replica from the Head Node which holds it and a Write operation

is the process of publishing or updating the Service information in each Head Node

of the DUDDI system. In the proposed Replica Management methodology, let

„N‟ be the number of message passes between the Head Node and the

node which is having the latest replica of the Service information.

„R‟ be the number of message passes between one Head Node to another

Head Node.

„M‟ be the number of message passes between a Head Node and a Leaf

Node.

„S‟ be the number of nodes in the DUDDI system.

„P‟ be the number of Leaf Nodes under each Head Node (it is considered

that the number of Leaf Nodes under every Head Node is almost the

same).

„U‟ be the number of nodes forming the DSTj dynamically from time t0 to

t1.

„V‟ be the number of nodes deleted/removed in DSTj dynamically from

time t0 to t1.

where, 1 ≤ M ≤ N ≤ S and 1 ≤ P ≤ S.

With this background, the total number of message passes required for a single

Read operation in a P2P based DUDDI system can be estimated as,

n (P2P DUDDI Readmsgpass) =(N+M)+(S*(N+M))+(N+M)+(S*(N+M))

= (2N + 2M + 2SN + 2SM) - (6.1)

130

When the value of „S‟ is high, then 2N and 2M are negligible when compared to SN

and SM. So, the Equation 6.1 can be rewritten as,

n(P2P DUDDI Readmsgpass) ≥ 2 S (N+M) - (6.2)

Thus the total number of message passes required for a single Read

operation in a P2P based DUDDI system is directly proportional to the number of

nodes in the DUDDI system. Whereas, in a DST structured P2P DUDDI, the total

number of message passes required for a single Read operation at time t0 is

estimated to be,

n(DST structured P2P DUDDI Readmsgpass) at t0 = (M)+(M)+(M)+(M * P)

- (6.3)

Equation 6.3 can be rewritten as,

n(DST structured P2P DUDDI Readmsgpass) at t0 ≥ 3M+(M * P)

- (6.4)

The total number of message passes required to insert a node into any

Distributed Spanning Tree is estimated as,

n(DST structured P2P DUDDI insert Nodemsgpass) = 1+1+(M+1)

= M + 3 - (6.5)

Total number of message passes required to remove a node from any

Distributed Spanning Tree is estimated as,

131

n(DST structured P2P DUDDI removeNodemsgpass) = M - (6.6)

The total number of message passes required for single Read operation in

DST structured P2P based DUDDI at time t1 with „U‟ being the number of nodes

inserted and „V‟ being the number of nodes removed from the Distributed Spanning

Tree is defined as,

n(DST structured P2P DUDDI Readmsgpass) at t1

= (M+3)+(M+U)+(M+U)+(M+U)+((M+U)*P)+(M*V)

- (6.7)

After neglecting (M+3), the Equation 6.7 can be rewritten as,

n(DST structured P2P DUDDI Readmsgpass) at t1 ≥ 3(M+U)+((M+U)*P)+(M*V)

- (6.8)

The total number of message passes required for a Read operation in the

DST structured P2P based DUDDI system increases proportionally with the value

of „U‟. Also, the Equation 6.4 and Equation 6.8 can be considered as the Best and

the Worst cases for the Read operation in the DST structure P2PDUDDI system

respectively.

Similarly, an analysis of the Write operation can also be described. The total

number of message passes required for single Write operation in P2P based

DUDDI system is,

n(P2P DUDDI Writemsgpass) = (N+M)+(S*(N+M))+(N+M)+(S*(N+M))

= (2N+2M+2SN+2SM) - (6.9)

132

Since 2N and 2M are negligible, Equation 6.9 can be re-written as

n(P2P DUDDI Writemsgpass) ≥ 2S(N+M) - (6.10)

Thus the total number of message passes required for a single Write

operation in a P2P based DUDDI system is directly proportional to the number of

nodes in the DUDDI system. The total number of message passes required for

single Write operation in DST structured P2PDUDDI is given by,

n(DST structured P2P DUDDI Writemsgpass) at t0

= M+(S/(P+1))*R+(S/(P+1))*R+M+(S/(P+1))*R - (6.11)

Since 2M is negligible and S/(P+1) equals the total number of Head Nodes

formed in the DUDDI System, which is n(HN). Equation 6.11 can be rewritten as,

≥ 3(R*S/(P+1))

n(DST structured P2P DUDDI Writemsgpass) at t0 ≥ 3*n(HN)*R - (6.12)

Now, the total number of message passes required for a single Write

operation in the DST structured P2P DUDDI system at time t1 with „U‟ being the

number of nodes inserted and „V‟ being the number of nodes removed from the

DST structure can be defined as,

n(DST structured P2P DUDDI Writemsgpass) at t1

=(M+3)+(M+U)+(S/(P+1))*(R+U-V)+(S/(P+1))*(R+U-V)+(M+U)+(S/P(P+1))*(R+U-V)+(M*V)

- (6.13)

Since (M+U), (M+V) and (M+3) are much smaller when considering large

values of „R‟ and S/(P+1), it equals the total number of Head Nodes formed in the

system, n(HN). Equation 6.13 can be rewritten as,

133

n(DST structured P2P DUDDI Writemsgpass) at t1 ≥ 3((R+U-V)*S/(P+1))+(M*V)

- 6.14

From Equation 6.14, it is understood that the total number of message passes

required for a Write operation in the DST structured P2P DUDDI increases with

the value of „U‟. Also, Equation 6.12 and Equation 6.14 can be considered as the

Best and the Worst cases for Write operation in DST structured P2P DUDDI

system respectively.

Comparison between the message passes of the Read and Write operations is

shown in Table 6.1. The values recorded in the Table 6.1 clearly demonstrates the

reduction in the total number of message passes required for each Read and Write

operation in a DST structured P2P DUDDI compared to the same in the P2P

DUDDI system. Though the Write operation looks complex in the DST structured

P2P DUDDI, it has its own unique features such as dynamic self-organisation,

replica consistency, less response time, etc... Since the Read operation is only

concerned with a particular DST structure on which the Read operation request has

been initiated, concurrent Read operations are made easily possible. Thus using

DST as the interconnection structure, it is proved that the Replica Management can

be effectively done in the P2P based DUDDI system with reduced number of

message passes and in least possible time, which are considered to be the critical

QoS parameters for the proposed system.

134

Table 6.1 Performance Comparison for Read/Write Operations Between

P2P DUDDI System and DST Structured P2P DUDDI System

S.

No.

READ OPERATION WRITE OPERATION

Operation Message passes

in P2PDUDDI

Message passes in

DST Structured

P2P DUDDI

Operation Message passes in

P2PDUDDI

Message passes in

DST Structured

P2P DUDDI

1 Read Request N+M M Write Request N+M M

2 Lock Message S*(N+M) Not Applicable Lock Message S*(N+M) (S/(P+1)) * R

3 Lock

Acknowledge Not Applicable Not Applicable

Lock

Acknowledge Not Applicable (S/(P+1)) * R

4 Read Reply N+M M Write Reply N+M M

5 Unlock Message S*(N+M) M Unlock Message S*(N+M) (S/(P+1)) * R

6 Wait Message Not Applicable ≤ M * P Wait Message Not Applicable ≤ M * P

135

6.3 EXPERIMENTAL ANALYSIS

This section describes the experimental setup, basically the simulation

using OMNET++, developed for investigating the proposed research work.

OMNeT++, an object-oriented, modular, discrete, event network simulator has

been used for the simulation of the proposed DUDDI system. A P2P based

DUDDI is simulated (comp1, comp2, comp3 …comp100) and all the nodes are

interconnected in a random fashion. Unit propagation delay of the transmission

medium has been assumed as 10 ms. The experimentation and analysis has been

carried out in two different phases which are as shown below.

Phase 1: Simple P2P DUDDI Vs DST Structured P2P DUDDI

Phase 2: Simple P2P DUDDI Vs DST structured P2P DUDDI Vs

ACO optimized DST structured P2P DUDDI.

6.3.1 P2P DUDDI Vs DST Structured P2P DUDDI

In this phase, the proposed model has been examined in two different

methods. Experiments of Method 1 have been designed such that to prove the role

of DST in improving the performance by reducing the number of message passes

for Replica Management (i.e. in reducing the number of message passes) in a P2P

based DUDDI and the experimentation was carried out in two different

environments, which are P2P DUDDI and the DST Structured P2P DUDDI.

Method 2 is aimed at assessing the contribution of DST in improving the

scalability of the overall environment, particularly from the Replica Management

perspective. Method 2 assessment has been carried out in four different

environments, which are Sparse P2P DUDDI, Sparse DST Structured P2P

DUDDI, Dense P2P DUDDI and Dense DST Structured P2P DUDDI.

136

6.3.1.1 Service Read/Write Based Assessments

Method 1: It has been designed such that to prove the role of DST in

improving the performance of Replica Management by reducing the number of

message passes in two different environments, which are P2P DUDDI and

DST structured P2P DUDDI. Method-1 examines the scalability of the system for

Read and Write operations. This experiment is to assess the scalability in terms of

accommodating more number of Read and Write operations. In accordance to this

experimental setup, Equation 6.1 is rewritten as,

- (6.15)

Where, the node numbers are to be preceded by the term ―comp‖. For

example, the DST1 should be interpreted as DST1 = (comp04, comp01…comp95),

in which the first node ―comp04‖ is the Head Node of DST1 and all other nodes

are Leaf Nodes of DST1 as given in the Equation 6.1.

In the simulated system, the Head Nodes of the DSTs are comp04, comp18,

comp36, comp54 and comp93. Obviously the other nodes act as Leaf Nodes under

the appropriate Head Nodes. The total number of Leaf Nodes under DST1, DST2,

DST3, DST4 and DST5 in the simulated system is 22, 16, 26, 17 and 14

respectively. These values show that the Leaf Nodes are not uniformly distributed

among the Head Nodes, which implies that the number of Leaf Nodes under the

corresponding Head Node depends on various criteria like the distance between

=

DST1

DST2

DST3

DST 4

DST5

04,01,02,05,06,11,17,26,37,40,57,46,58,66,70,71,72,75,84,86,89,94,95

18,12,31,03,20,21,22,35,38,19,52,53,59,62,81,55,65

36,27,28,07,23,30,14,29,39,41,43,44,60,61,63,68,69,76,77,67,79,80,85,87,88,90,96,97

54,51,42,09,25,45,32,48,13,45,49,50,56,64,78,73,74,83

93,92,91,10,08,24,33,34,16,47,54,98,99,100,82

137

them, channel capacity, congestion on a particular region, user approval, etc.,. In

principle, the message passes required for each node and for the overall system

can be defined as shown in the Equation 6.16 and Equation 6.17.

Definition 1: Let P(i) be a node. For P(i) to be part of a DST, the number of

message passes required can be defined as,

n(P(i)msg = - 6.16

Where,

n(P(i)msg is the number of message passes required by the node P(i) to become

the member of a DST, and i=1, 2, 3…..s. and „s‟ is the total number of nodes in

the system.

„r‟ is the number of nodes directly connected with P(i).

Definition 2: Let n(DSTmsg) be the total number of message passes required

by all the nodes in the system to form the DSTs which is given as,

- 6.17

Where, ‗s‘ is the total number of nodes in the system.

Equation 6.16 and Equation 6.17 help to estimate the number of message

passes required to convert the entire P2P DUDDI system into a number of logical

DST structured P2P DUDDI. From the simulation results, the value of n(DSTmsg)

is found to be 437 and the time taken to form the entire DST structured

P2P DUDDI is 6.39 seconds. It is also observed that around 124 Read operations

have been performed by 50 nodes in the first 100 seconds in the DST structured

P2P DUDDI, whereas it is only 72 Read operations been performed by 41 nodes

r, if P(i) = HN

r + 1, if P(i) ≠ HN

s

i

msgimsg PnDSTn0

)( )()(

138

for the same period in the simple P2P DUDDI. The values obtained through the

simulation are given in Table 6.2.

Table 6.2 Performance Comparison between P2P DUDDI System and

DST Structured P2P DUDDI System for Service Read and Write

Sl.

No. Performance Criteria

Simple P2P

DUDDI

DST

Structured

P2P DUDDI

1 No. of Messages to formulate the system NA 437

2 Time taken to formulate the system (in sec) NA 6.39

3 No. of read operations performed in first

100 seconds 72 124

4 No. of nodes involved in read operation in first

100 seconds 41 50

5 No. of write operations performed in first

100 seconds 28 51

6 No. of nodes involved in write operation in first

100 seconds 21 25

Thus, using DST as an interconnection structure, efficiency of the proposed

P2P DUDDI system can be improved upto 85% in the overall Read operations

by the way of reducing the number of required message passes. This is clearly

visible from the Figure 6.1. Similarly, it can also be observed that there are 51

Write operations performed by 25 nodes in the first 100 seconds in DST

structured P2P DUDDI, whereas there are only 28 Read operations performed by

21 nodes for the same period in the Simple P2PDUDDI. These values are

presented in Table 6.2. It can be clearly visible that the efficiency of the Write

operations on the P2P DUDDI system can be improved upto 80% by reducing

the number of message passes required for Write operations using DST Structure

in P2PDUDDI. This improvement is clearly visible from the Figure 6.2.

139

Figure 6.1 Comparison between the Simple P2P DUDDI and DST Structured P2P DUDDI in terms of Overall Read Operations

Figure 6.2 Comparison between the P2P DUDDI and DST Structured P2P DUDDI in terms of Overall Write Operations

com

p0

1

com

p0

2

com

p0

4

com

p1

1

com

p1

2

com

p1

6

com

p1

7

com

p1

8

com

p1

9

com

p2

2

com

p2

3

com

p2

4

com

p2

7

com

p2

8

com

p3

0

com

p3

2

com

p3

3

com

p3

4

com

p3

8

com

p4

0

com

p4

2

com

p4

7

com

p4

8

com

p4

9

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p5

1

com

p5

4

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p5

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p5

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p5

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p5

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p6

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p6

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p7

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p8

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p8

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p8

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p9

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p9

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com

p9

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p9

5

com

p9

8

0

2

4

6

8

10

Simple P2P DUDDI DST Structured P2P DUDDI

0

1

2

3

4

5

com

p0

2

com

p0

3

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p0

4

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p0

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p1

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p1

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p1

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p2

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p2

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p5

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p7

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p7

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com

p8

2

Simple P2P DUDDI DST Structured P2P DUDDI

No. of

Rea

d O

per

atio

ns

Per

form

ed

No. of

Wri

te O

per

atio

ns

Per

form

ed

Leaf Nodes

Leaf Nodes

140

6.3.1.2 Assessment of Scalability

Method 2: In Method 2, experiments have been designed such that to

assess the scalability of the proposed environment, particularly from the Replica

Management perspective. Technically, P2P DUDDI is analyzed based on the

factor, the communication cost, which is the cost measure associated with the link

between any two nodes defined by its link‘s physical properties like distance,

capacity, etc. Here, if the communication cost is high then the nodes of the system

are considered to be spatially distributed sparse and the same is dense incase if the

communication cost is less.

A DUDDI system has been simulated with 103 nodes (10 times the size

considered for Method-1 experimental environment) for each type and the

analysis has been carried out in four different environments, which are

1) Sparse P2P DUDDI, 2) Sparse DST structured P2P DUDDI, 3) Dense

P2P DUDDI and 4) Dense DST structured P2P DUDDI

The system has been observed for the first 100 seconds and the results are

tabulated in Table 6.3. Here, the Success Ratio (SR) is defined as the ratio

between the number of Read/Write request made and the number of successful

Read/Write operations performed in a particular interval of time. The QoS values

derived from the set of values of the Table 6.3 are presented in Table 6.4 and the

same has been graphically represented as shown in Figure 6.3, Figure 6.4,

Figure 6.5 and Figure 6.6. The Figure 6.3 corresponds to the message density of

the system, which is defined as the total number of messages on the system, being

utilized for communication among the nodes at a particular time period.

Figure 6.4 corresponds to the number of message passes by unsuccessful

Read/Write operations at a particular time period. Figure 6.5 and Figure 6.6 show

the success ratio of Read and Write operations performed under different

scenarios respectively. Average is the average message density, average number

of message passes, average success ratio in Read/Write operations, as in the

Figure 6.3, Figure 6.4, Figure 6.5 and Figure 6.6 respectively.

141

Table 6.3 Performance Comparison between P2P DUDDI and DST Structured P2P DUDDI

Table 6.3.1: Read Operation

S. No

Simulation

Time Interval

(s)

READ OPERATION

SPDUDDI SDDUDDI DPDUDDI DDDUDDI

RR RS SR RR RS SR RR RS SR RR RS SR

1 0-10 21 16 76.2% 22 20 90.9% 19 16 84.2% 29 28 96.6%

2 10-20 17 13 76.5% 21 18 85.7% 17 15 88.2% 26 24 92.3%

3 20-30 17 12 70.6% 19 17 89.5% 19 16 84.2% 24 23 95.8%

4 30-40 18 15 83.3% 21 18 85.7% 19 17 89.5% 26 25 96.2%

5 40-50 18 13 72.2% 22 19 86.4% 18 15 83.3% 28 26 92.9%

6 50-60 21 15 71.4% 20 18 90.0% 21 16 76.2% 31 29 93.5%

7 60-70 18 13 72.2% 18 16 88.9% 19 13 68.4% 29 25 86.2%

8 70-80 18 11 61.1% 21 16 76.2% 18 12 66.7% 23 21 91.3%

9 80-90 15 10 66.7% 19 15 78.9% 18 13 72.2% 25 22 88.0%

10 90-100 14 9 64.3% 21 16 76.2% 19 12 63.2% 23 21 91.3%

SPDUDDI - Sparse P2PDUDDI RR - Read Request WR - Write Request

SDDUDDI - Sparse DST P2PDUDDI RS – Read Success WS – Write Success

DPDUDDI - Dense P2PDUDDI SR – Success Ratio

DDDUDDI - Dense DST P2PDUDDI

142

Table 6.3 Performance Comparison between P2P DUDDI and DST Structured P2P DUDDI

Table 6.3.2: Write Operation

SPDUDDI - Sparse P2PDUDDI RR - Read Request WR - Write Request

SDDUDDI - Sparse DST P2PDUDDI RS – Read Success WS – Write Success

DPDUDDI - Dense P2PDUDDI SR – Success Ratio

DDDUDDI - Dense DST P2PDUDDI

Sl. No

Simulation

Time Interval

(sec)

WRITE OPERATION

SPDUDDI SDDUDDI DPDUDDI DDDUDDI

WR WS SR WR WS SR WR WS SR WR WS SR

1 0-10 3 2 66.7% 4 3 75.0% 4 3 75.0% 6 6 100%

2 10-20 3 3 100% 5 4 80.0% 6 5 83.3% 6 4 66.7%

3 20-30 5 4 80.0% 5 5 100% 6 4 66.7% 7 7 100%

4 30-40 4 2 50.0% 6 5 83.3% 5 3 60.0% 6 6 100%

5 40-50 7 5 71.4% 7 6 85.7% 6 5 83.3% 4 4 100%

6 50-60 5 2 40.0% 6 5 83.3% 5 3 60.0% 9 8 88.9%

7 60-70 7 3 42.9% 4 3 75.0% 6 4 66.7% 11 8 72.7%

8 70-80 8 4 50.0% 6 5 83.3% 6 5 83.3% 7 7 100%

9 80-90 9 3 33.3% 7 5 71.4% 7 3 42.9% 7 6 85.7%

10 90-100 5 2 40.0% 3 2 66.7% 5 3 60.0% 5 4 80.0%

143

Table 6.4 Performance Comparison Between

Simple P2P DUDDI and DST P2P DUDDI Under Different Test Scenarios

S.No QoS Factor SPDUDDI SDDUDDI DPDUDDI DDDUDDI

1 Time taken to create the system

with technique (in sec) NA 29.32 NA 22.29

2 Time taken for 100 Read

operations (in sec) 78 56 69 41

3 Time taken for 100 Write

operations (in sec) 342 244 272 169

4 Average no. of message passes

required for a Read operation > 49 26 41 18

5 Average no. of message passes

required for a Write Operation 81 55 73 46

6 Message density in the system

after 100 seconds 10.23 x103 6.19 x103 9.2 x103 3.3 x103

7 Overall Success Ratio for Write

operation 53.6% 81.6% 67.9% 88.2%

8 Overall Success Ratio for Read

operation 74.5% 84.8% 80.6% 92.4%

SPDUDDI - Sparse P2PDUDDI

SDDUDDI - Sparse DST P2PDUDDI

DPDUDDI - Dense P2PDUDDI

DDDUDDI - Dense DST P2PDUDDI

144

Figure 6.3 Message Density with respect to Time in Different Conditions

Figure 6.4 Message Passes of Unsuccessful Read/Write Operations

0

2000

4000

6000

8000

10000

12000

Sparse P2P DUDDI Sparse DST Structured P2P DUDDI

Dense P2P DUDDI Dense DST Structured P2P DUDDI

0

100

200

300

400

500

600

700

800

10 20 30 40 50 60 70 80 90 100 Average

Sparse P2P DUDDI Sparse Structured DST P2P DUDDI

Dense P2P DUDDI Dense DST P2P DUDDI

Simulation Time (sec)

Mes

sage

Den

sity

Simulation Time (sec)

No. of

Mes

sage

Pas

ses

145

Figure 6.5 Success Ratio of Read Operation

Figure 6.6 Success Ratio of Write Operation

40%

60%

80%

100%

Sparse P2P DUDDI Sparse DST Structured P2P DUDDI

Dense P2P DUDDI Dense DST Structured P2P DUDDI

0%

20%

40%

60%

80%

100%

Sparse P2P DUDDI Sparse DST Structured P2P DUDDI

Dense P2P DUDDI Dense DST Structured P2P DUDDI

Succ

ess

Rat

io

Simulation Time (sec)

Succ

ess

Rat

io

Simulation Time (sec)

146

The overall success ratio of Write operation has increased from 53.6% to

81.6% from Sparse P2P DUDDI to Sparse DST P2P DUDDI and thereby the

advantage of the application of DST structures in P2P DUDDI is shown visibly.

Similarly, the overall success ratio of Read operation has also increased from

74.5% to 84.8% due to the application of the DST structures. Also, when the

Dense P2P DUDDI and Dense DST P2P DUDDI is compared, the overall success

ratio of the Write operation has increased from 67.9% to 88.2% and the same for

the Read operation has also increased from 80.6% to 92.4% which is again due to

the application of the DST structures. Hence it is proved that the application of

DST structures over the P2P DUDDI system contributes to the improvement of

the overall efficiency of the Replica Management in the proposed DUDDI system.

6.3.2 P2P DUDDI Vs DST P2P DUDDI Vs ACO Optimized DST P2P DUDDI

In this phase of analysis, the proposed system has been examined in three

different environments based on important issues in Service Replica Management

such as consistency, availability and the response time. For analysis,

experimentation setup established as said in Chapter 4 has been used with

different values for Service request generation with an additional change that the

ACO optimization is performed in the proposed DST structured P2P DUDDI

system. To route a replica request message from a requesting node to a SRL node,

where the requested replica is available, Ant Colony Optimized routing technique

has been tried, which is proved to be efficient in terms of the number of message

passes and response time, because of the dynamically identified optimal route

between every SRL node and the Service requesting nodes. Formulation of Ant

Colony Optimization of DST structured P2P DUDDI is the next step after the

implementation of DST structures in the P2P DUDDI, which is achieved by

sending Probe Request messages from Head Node to its Leaf Nodes and Head

Nodes to all other Head Nodes.

147

During the process of simulation, it has been observed that nearly 189 Read

operations have been performed by nearly about 59 nodes in 600 seconds (with a

delay of 100 ms). Thus the number of message passes for Read operation has been

proved reducing at a greater extent by using Ant Colony Optimization in the

DST structured P2P DUDDI and the Read operations are performed faster and

consistent as is been shown through the results.

As far as the Write operations are concerned, during the simulation, it is

found that about 23 Write operations have been performed by 16 nodes in 30

seconds. The outcome of the result analysis shows that the ACO optimized

DST structured P2P DUDDI can perform Read/Write operations at higher speed

and with consistency than it is without these techniques on them. Table 6.5 shows

a straight comparison of a DST structured P2P DUDDI with an ACO optimized

DST structured P2P DUDDI for various performance criteria measures identified

(Chapter 3). The comparison proves that for a propagation delay of 100 ms, the

number of Read/Write operations performed can be greatly improved by

optimizing the DST structured P2P DUDDI system with ACO.

Based on the results displayed in Table 6.5, it is clearly visible that the

ACO optimized DST strucutred P2P DUDDI system can perform the operations

nearly 50% faster than the simple DST structured P2P DUDDI system. The

simulation has been done for a channel of propagation delay set to 100ms. The

system‘s response could be further sped up by decreasing the propagation delay.

148

Table 6.5 Comparison Between

DST P2P DUDDI System and ACO Optimized DST P2P DUDDI System

S.No Measurement Criteria DST

P2PDUDDI

ACO

Optimized DST

P2PDUDDI

1 No. of Messages created to formulate the technique 437 220

2 Time taken to formulate the technique (in sec) 6.39 3.14

3 No. of Read operations performed in 600 sec 121 181

4 No. of Nodes involved in Read Operation in 600 sec 49 56

5 No. of Write operations performed in 30 sec 17 25

6 No. of Nodes involved in Write Operation in 30 sec 16 18

Table 6.6 Comparison of

P2P DUDDI Vs DST P2PDUDDI Vs ACO Optimized DST P2P DUDDI

With Respect to Various QoS Factors - Propagation Delay:10ms

S.

No QoS Factor P2PDUDDI

DST

P2PDUDDI

ACO

Optimized

DSTP2PDU

DDI

1 Time Taken to create network with

technique (in sec) NA 6.39 9.33

2 Time Taken for 100 Read Operations

(in sec) 69 45 36

3 Time Taken for 100 Write Operations

(in sec) 32 24 14

4 Average no. of Message Pass

required for a Read Operation 81 7 7

5 Average no. of Message Pass

required for a Write Operation 87 46 35

Based on the results of the simulation and the measured values of the

various QoS parameters, it is highly visible that the performance of a DST

structured P2P DUDDI is more when compared to that of the simple P2P DUDDI

and further the performance of ACO Optimized DST structured P2P DUDDI is

149

still more better when compared to the DST structured P2P DUDDI, which is

obvious when looking at the numeric figures at the Table 6.6.

6.3.2.1 Service Consistency Evaluation

Consistency Management of a Service item or its replica is a crucial issue

which directly influences the overall efficiency of the Replica Management

methodology. Web Service information or its replica updations are not so frequent

as the way the Distributed Database replicas are updated. Since the frequency of

updations of Web Services information is less, in the proposed DUDDI system, a

simple consistency model is just enough to keep the consistency and hence the

time based consistency model has been chosen, which is simple and effective for

Service / Replica consistency management applications.

Let Di be the Service/Replica item which is cached at time ‗Tc‟, then the

validity of the Service item is TRUE at time Tr, at which the Service request was

received, if it satisfies the condition, Tc + T < Tr . Here „Tc‟ is the time at

which Service item is cached in cache node, ‗Tr‘ is the time at which the Service

item is requested by a node and „T‟ is the validity period of the Service item

within the DUDDI system.

Every Head Node which stores the Service/Replica item also stores

metadata about the Service item Di which contains the time at which Di is being

cached. This information is used to check the validity of Service item. „T‟ is a

constant which varies based on the Service item being updated.

100× cached item serviceno.of Total

use before expired item serviceno.of Total-cached item serviceno.of Total

=usage item serviceconsistent of %

150

The measure used to evaluate the consistency can be defined as the ratio

between the number of Service item requests serviced to the sum of requests

served and the number of Service items expired before its usage. This can be

expressed as shown in Table 6.7, which shows the consistency statistics of the

sample Leaf Nodes in P2P DUDDI, DST structured P2P DUDDI and the ACO

optimized DST structured P2P DUDDI.

Also, Table 6.7 gives the experimental results for the number of Service

items expired before being used by any requesters, which shows that the services

replica is available in a Head Node where there are no users, i.e., the Service

requestors. A better Service replica utility can be seen from the figures of the

table, which proves that the Service replica utility is more in the

DST structured P2P DUDDI system when compared to the simple P2P DUDDI

system and the utility is further improved in ACO optimized DST structured P2P

DUDDI compared to the other two systems, which is shown in Figure 6.7. From

these statistics, it can be observed that the effective usage of cached Service items

are much improved in DUDDI with DST and ACO optimized DST schemes.

Compared to the traditional DUDDI approach, as per the illustration in the Figure

6.7 and Figure 6.8, the proposed techniques display improved performance.

151

Figure 6.7 Consistency in P2P DUDDI Vs DST P2P DUDDI Vs

ACO Optimized DST P2PDUDDI

Figure 6.8 Number of Service Items Expired Before Utilization in

P2P DUDDI Vs DST P2P DUDDI Vs ACO Optimized DST P2PDUDDI

0%

20%

40%

60%

80%

100%

P2P DUDDI DST Structured P2P DUDDI ACO Optimized DST P2P DUDDI

0

0.5

1

1.5

2

2.5

3

3.5

P2P DUDDI DST Structured P2P DUDDI ACO Optimized DST P2P DUDDI

Consi

sten

cy (

% )

Leaf Nodes

No. of

Ser

vic

e it

ems

expir

ed

Leaf Nodes

152

Table 6.7 Consistency in P2P DUDDI Vs DST Structured P2P DUDDI Vs ACO Optimized DST P2P DUDDI

S. No LN

P2PDUDDI DST Structured P2PDUDDI ACO Optimized DSTP2PDUDDI

No. of

data item

cached

No. of

data item

request

served

No. of

data

items

deleted

before

use

% of data

item used

before

consistenc

y expires

No. of

data

item

cached

No. of

data item

request

served

No. of

data

items

deleted

before

use

% of data

item used

before

consistenc

y expires

No. of

data

item

cached

No. of

data item

request

served

No. of

data

items

deleted

before

use

% of data

Item used

before

consistency

expires

1 comp02 2 9 1 50% 8 26 1 87.5% 9 23 2 77.7%

2 comp06 8 16 1 87.5% 5 12 2 60% 4 10 1 75.0%

3 comp09 5 11 2 60% 4 15 0 100% 5 15 0 100.0%

4 comp13 4 13 1 75% 3 9 1 66.6% 3 11 1 66.6%

5 comp17 3 6 1 66.6% 3 18 0 100% 4 16 0 100.0%

6 comp21 5 13 2 60% 5 23 2 60% 6 22 0 100.0%

7 comp24 4 12 2 50% 6 19 3 50% 7 26 2 71.4%

8 comp26 4 17 1 75% 5 14 1 80% 4 21 1 75.0%

9 comp29 5 21 3 40% 6 26 2 66.6% 8 23 2 75.0%

10 comp32 2 10 1 50% 3 21 0 100% 5 21 1 80.0%

11 comp37 1 0 1 0% 2 15 0 100% 4 19 0 100.0%

12 comp43 3 0 3 0% 5 9 2 60% 3 16 1 66.6%

13 comp46 2 5 1 50% 6 18 3 50% 6 21 2 66.6%

14 comp47 4 21 1 75% 3 12 1 66.6% 2 16 0 100.0%

15 comp49 3 8 2 33.3% 3 7 0 100% 5 14 1 80.0%

153

6.3.2.2 Assessment of Availability

Availability is defined as the ratio between the number of times a service

item is served to the total number of times it is requested or expected to be served.

This can be expressed as,

Since the operations in every DST are performed through Head Nodes, it

may easily become the traffic bottleneck and single point of failure of the DST.

Failure of the Head Node would contribute to a decrease in the availability of the

service item since the details about the Leaf Node which hold the cached service

cannot be accessed after the failure of the Head Node.

So, every Head Node operations are monitored and if any Head Node fails

and the failure period exceeds the set threshold time, then any Leaf Node adjacent

to that Head Node, which also satisfies the test conditions to become the Head

Node, will act as Head Node. This reduces the traffic in the existing Head Node.

Thus the dynamic selection of Head Node increases the availability of the cached

Service item.

The Service availability statistics of these approaches from the

experimental results have been tabulated in Table 6.8. Also, Table 6.8 tabulates

the experimental results for Service Ratio, which is a ratio between the total

number Services served and the total number of Services requested. The

performance of the DUDDI system after having DST structures and ACO

optimized has improved in terms of the Service Availability and the Service Ratio

which is illustrated in Figure 6.9 and in Figure 6.10. It proves the enhanced

performance of the proposed methodologies in comparison with the traditional

P2P DUDDI system.

100× failure LN cached to due dropped request no.of Total+ servedrequest item serviceno.of Total

servedrequest item serviceno.of Total

=tyavailabili item serviceof %

154

Table 6.8 Availability in P2P DUDDI Vs DST Structured P2P DUDDI Vs ACO Optimized DST P2P DUDDI

S.

No HN

P2PDUDDI DST Structured P2PDUDDI ACO Optimized DSTP2PDUDDI

No. of

requests

received

(A)

No. of

requests

served

(B)

Service

ratio

(A/B)

No. of

requests

dropped

due to

cached

LN

unavailab

ility

% of data

item

available

No. of

requests

received

(A)

No. of

requests

served

(B)

Service

ratio

(A/B)

No. of

request

dropped

due to

cached

LN

unavaila

bility

% of data

item

available

No. of

requests

received

(A)

No. of

requests

served

(B)

Service

ratio

(A/B)

No. of

request

dropped

due to

cached

LN

unavaila

bility

% of data

item

available

1 comp04 112 91 81.25% 21 81.2% 170 158 92.94% 12 92.9% 178 169 94.94% 9 94.9%

2 comp18 132 120 90.91% 12 90.9% 206 197 95.63% 9 95.6% 219 208 94.98% 11 94.9%

3 comp36 154 135 87.66% 19 87.6% 148 132 89.19% 16 89.2% 158 146 92.41% 12 92.4%

4 comp55 98 89 90.82% 9 90.8% 165 154 93.33% 11 93.3% 181 172 95.03% 9 95.0%

5 comp56 119 90 75.63% 29 75.6% 157 145 92.36% 12 92.4% 166 158 95.18% 8 95.1%

6 comp93 154 135 87.66% 19 87.6% 170 158 92.94% 12 92.9% 219 208 94.98% 11 94.9%

155

Figure 6.9 Availability with respect to Head Nodes of

P2P DUDDI Vs DST P2P DUDDI Vs ACO DST P2P DUDDI

Figure 6.10 Service Ratio with respect to Head Nodes of

P2P DUDDI Vs DST P2P DUDDI Vs ACO DST P2P DUDDI

50%

60%

70%

80%

90%

100%

comp04 comp18 comp36 comp55 comp56 comp93

P2P DUDDI DST Structured P2P DUDDI ACO Optimized DST P2P DUDDI

70%

80%

90%

100%

comp04 comp18 comp36 comp55 comp56 comp93

P2P DUDDI DST Structured P2P DUDDI ACO Optimized DST P2P DUDDI

Avai

labil

ity

( %

)

Head Nodes

Ser

vic

e R

atio

( %

)

Head Node

156

6.3.2.3 Assessment of Response Time

Response Time is a critical performance measure which refers to the process

of visiting each node in a DST structured P2P DUDDI exactly once, in a systematic

way at comparatively low number of hops, i.e, through a shortest path. To analyze

the performance of the proposed system in terms of the Response Time, the number

of hops need to be passed through, for every Service item request by a requester,

before reaching the nearest Head Node which carries the requested Service item or

its replica, is considered. The Response Time in terms of the number of hop count

for a Service item request in all the three environments under study has been

tabulated in Table 6.9. Also, the experimental results for a Leaf Node to reach its

Head Node and the number hops that it has to traverse to reach the Head Node are

tabulated in Table 6.9.

The tabulated data proves that the response time is better and the number of

hops to be traversed by a Leaf Node to reach its Head Node is minimized in the

ACO optimized DST structured DUDDI system, compared to the other two

systems. This system‘s efficiency in terms of response time and the number of hop

counts to reach the Head Node is shown in the Figure 6.11 and Figure 6.12

respectively. It is clear from the experimental results given in the Table 6.9 and

from the Figure 6.11 and Figure 6.12 that the approach of P2P DUDDI system with

the DST structured node distribution has better performance in terms of Response

Time and less number of hops to traverse to reach the Head Node. Also, the

Response Time is still better when the ACO optimized DST structured P2P UDDI

is compared with the other two systems. The difference of performance in these

systems in terms of the Response Time and the number of hop counts is clearly

illustrated in the graphs as shown in the Figure 6.11 and Figure 6.12 respectively.

157

Table 6.9 Response Time for Service Requests in

P2P DUDDI Vs DST P2P DUDDI Vs ACO Optimized DST P2P DUDDI

S.

No LN

P2PDUDDI DST P2PDUDDI ACO Optimized DSTP2PDUDDI

Number of hops required to

identify the nearest HN for

each data item request

Average

Hop

count

required

for first

HN

traversal

Average

Time

taken

for first

HN

traversal

(ms)

Number of hops required to

identify the nearest HN for

each data item request

Average

Hop

count

required

for first

HN

traversal

Average

Time

taken

for first

HN

traversal

(ms)

Number of hops required

to identify the nearest HN

for each data item request

Average

Hop

count

required

for first

HN

traversal

Average

Time

taken

for first

HN

traversal

(ms)

Rq 1 Rq 2 Rq 3 Rq 4 Rq 5 Rq 1 Rq 2 Rq 3 Rq 4 Rq 5 Rq 1 Rq 2 Rq 3 Rq 4 Rq

5

1 comp02 6 4 6 - - 3.3 39.6 3 2 2 - - 2.3 27.6 1 2 2 - - 1.6 27.6

2 comp06 5 8 3 - 3.3 39.6 2 3 1 1 - 2 24 1 3 1 1 - 1.5 18

3 comp09 2 5 8 3 12 6 72 2 3 1 4 2 2.4 28.8 3 2 3 2 1 2.2 28.8

4 comp13 5 6 - - - 5.5 66 5 2 - - - 3.5 42 3 1 - - - 2 24

5 comp17 - - - - - - - - - - - - - - - - - - - - -

6 comp21 7 8 - - - 7.5 90 3 2 - - - 2.5 30 2 3 - - - 2.5 30

7 comp24 7 8 2 - - 5.6 67.2 3 1 4 - - 2.6 31.2 2 1 3 - - 2 24

8 comp26 11 3 8 - - 7.3 87.6 4 3 1 - - 2.6 31.2 4 2 1 - - 2.3 27.6

9 comp29 3 6 2 - - 3.6 43.2 1 2 4 3 - 2.5 30 2 1 2 3 - 2 24

10 comp32 6 3 10 3 - 5.5 66 2 2 2 3 - 2.25 27 1 2 2 3 - 2 24

11 comp37 1 5 - - - 3 36 1 3 - - - 2 24 1 2 - - - 1.5 18

12 comp43 6 5 2 - - 4.3 51.6 6 2 1 - - 3 36 3 1 2 - - 3 36

13 comp46 - - - - - - - - - - - - - - - - - - - - -

14 comp47 6 13 1 - - 6.6 79.2 3 4 1 - - 2.6 31.2 3 3 1 - - 2.3 27.6

15 comp49 3 5 6 - - 4.6 55.2 1 2 1 - - 1.3 15.6 1 1 1 - - 1 12

158

Figure 6.11 Average Time Taken to Service the Requests by Leaf Nodes

Figure 6.12 Number of Hop Counts Required to Identify the

Nearest Head Node for Each Service Item Request

0102030405060708090

100

DST Structured P2P DUDDI P2P DUDDI ACO Optimized DST P2P DUDDI

0

1

2

3

4

5

6

7

8

P2P DUDDI DST Structured P2P DUDDI ACO Optimized DST P2P DUDDI

Tim

e ta

ken

(m

s)

Leaf Nodes

Hop C

ounts

Leaf Nodes

159

6.4 SUMMARY

The reason why the research topic has been chosen on Service Consistency

and related issues in a Distributed UDDI registry has been well established

through the discussions of the Chapter 1 and Chapter 2. Having identified the

research domain, the goals of the research work have been identified and

presented in the Chapter 3. Based on the set goals, necessary infrastructure

modeling has been done and explained through the Chapter 4. Experimentation

was conducted in the test bed, which was established through OMNET++, for

assessing the performance of the proposed DUDDI system. The experimental

results have been analyzed in this Chapter for assessing the performance of the

proposed DUDDI system in three variants viz., 1) A Traditional P2P based

DUDDI System, 2) A DST structured P2P based DUDDI system and 3) ACO

optimized DST structured P2P DUDDI system.

While evaluating the performance of the proposed DUDDI system, it is

identified that the application of DST structures on the proposed P2P DUDDI

system has contributed to the improvement in the total number of Read and Write

operations performed. Also, the Success Ratio for the Service Read request and

Write request is better in the DST structured P2P DUDDI system compared to the

traditional P2P DUDDI system, as shown in the Section 6.3.1. While the Section

6.3.1 proves the improvement in performance after the application of DST

structures in the traditional P2P DUDDI system, the Section 6.3.2 analyzes the

ACO optimized DST structured P2P DUDDI system with the simple DST

structured P2P DUDDI system. Results and its analysis from the set of tables and

graphs have shown appreciable performance improvements with respect the

Service Consistency, Service Availability and the Response Time for Service

Read and Write requests. Therefore, it is evident that the proposed DST structured

DUDDI system with ACO optimization can offer an effective and efficient

Replica Management system with good response time and least possible number

of message exchanges.