E-MQTT: End-to-End Synchronous and Asynchronous Communication Mechanisms in MQTT Protocol

Round 1

Reviewer 1 Report (Previous Reviewer 1)

Comments for Authors

I want to encourage the authors for their research work. The authors should add the following suggestions for the consideration of the manuscript.

1.     What is the novelty of the present research work?

2.     The authors must add recent advancements in Message Queuing Telemetry Transport in the current scenario.

3.     The research methodology needs to be clarified.

4.     The authors should focus on the previous five years' research works.

5.     Elaborate the figure 20.

6.     The authors must compare the contribution of the proposed E-MQTT with previous research works.

7.     Modify the conclusion section for better clarification of the present research outcomes.

The English language presented in the manuscript needs moderate editing.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report (Previous Reviewer 2)

The paper describe a proposed new protocol E-MQTT that extends MQTT by adding end-to-end 4-way acknowledgment features between the 2 pairs: publisher-broker and broker-subscribers.

The content of the paper was extended and improved compared to the first submission and the pesentation is more clear now.

All the problems mentioned in the previous review were properly solved.

Author Response

We thank the reviewer for accepting the resubmitted manuscript.

Reviewer 3 Report (Previous Reviewer 3)

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Comments for author File: Comments.pdf

Good.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report (Previous Reviewer 3)

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Comments for author File: Comments.pdf

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This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

Response for Authors

The present study proposed an end-to-end communication mechanism of Message Queuing Telemetry Transport (MQTT): E-MQTT. The performance of the proposed E-MQTT has been evaluated through delay and packet size measurements in various situations. The manuscript has been poorly written, and its content is not up to date according to the needs of the current scenario. The authors must improve their manuscript by including the following suggestions.

1.     The abstract should be written systematically.

2.     In the introduction, page 1, lines 33-36, MQTT is used in a variety of applications, including resource-limited environments such as Machine to Machine (M2M) and Internet of Things (IoT) contexts. MQTT is also used in messengers and social networking systems. Elaborate this statement with other applications.

3.     In the introduction, page 2, line 54-58, there have been researches to extend MQTT functionalities, to compare MQTT with other protocols and to improve MQTT in the aspect of synchronous and asynchronous communications. However, they do not consider the problem of end-to-end communication between the publisher and the subscriber. What do you mean by it?

4.     In the literature review section, the authors should add recent research works.

5.     The authors must review the latest research works.

6.     What are the sources of Figures 8,9,10,11, and 12?

7.     Elaborate table 2.

8.     In the conclusion section, state more clearly how and in what way the proposed e-MQTT has been validated.

9.     Several research works have been done on this problem, So the authors must compare the contribution of the proposed E-MQTT with previous research works.

The English language presented in the manuscript needs moderate editing.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The paper describes and evaluates a proposed new protocol, E-MQTT, that extends MQTT by adding end-to-end 4-way acknowledgment features between the 2 pairs: publisher-broker and broker-subscribers.

In the first two sections E-MQTT is presented in its synchronous variant as publisher indicating a list from which it waits for an answer. That list is to be obtained using a query from the broker.

In fact, according to the Figure 1, the broker sends the published message only to the subscribers indicated by the publisher. That means that not all the subscribers of that topic receive any published message on that topic, but only those selected by the publisher.

My question is: are all the subscribers aware of that situation, i.e. there will be messages published on the respective topic that they will never receive unless the publisher explicitly want to?

I think a more general case can be considered, so 2 subscriber actions has to be described starting with Figure 1: one of a subscriber whose id is specified by the publisher and another of a subscriber whose id is not in the id list provided by the publisher.

So, the broker should count only PUBREC packets received from subscribers whose ids are in the id list provided by the subscriber.

It would be of interest how much this more general approach affects the delays measured in section 5.

Also, in section 5 is not specified if in the synchronous E-MQTT conducted tests the number of subscribers represents the count parameter of the publisher message or is the size of id list, and if they were equal or not.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

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Comments for author File: Comments.pdf

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Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Response for Authors

I didn’t find substantial answers and modifications.  I believe the manuscript is not suitable for publication and should be rejected.

The English language presented in the manuscript needs moderate editing.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

This manuscript has undergone significant revisions, resulting in a significant improvement in quality. The comments of the reviewers were well responded to one by one, and no obvious quality issues were found throughout the entire text. I tend to accept it.

This manuscript has undergone significant revisions, resulting in a significant improvement in quality. The comments of the reviewers were well responded to one by one, and no obvious quality issues were found throughout the entire text. I tend to accept it.

Round 3

Reviewer 1 Report

Response for the Authors

I have rejected the manuscript because I didn’t find substantial answers and modifications.

The English language presented in the manuscript needs moderate editing.

Author Response

Point 1

I have rejected the manuscript because I didn’t find substantial answers and modifications.

Answer1: We thank the comments of the reviewer. Although we have tried our best to answer all the questions and comments with the revised manuscript and response letter, probably it could not satisfy the reviewer. It would have been nice if the reviewer informed us which points lacked in our answer.