Computer Networks and Operating Systems: Consensus Protocols Report

This report examines the application of consensus protocols in the context of unreliable networks, focusing on challenges posed by misbehaving agents and faulty components. It delves into the complexities of security in networks dealing with clock synchronization, motion coordination, and cooperative estimation. The report identifies key challenges such as data delivery, data integrity, and security threats, while also exploring the role of consensus protocols in addressing these issues. It discusses various applications of consensus protocols, including transaction processing, leader election, state machine replication, and atomic broadcasts. A critical analysis of the effectiveness of these protocols is provided, along with a discussion of the limitations of techniques like internet content filters and firewalls. The report concludes by emphasizing the importance of consensus protocols in securing distributed systems and the need for continuous improvement to mitigate potential risks.

COMPUTER NETWORKS AND OPERATING SYSTEMS
Computer Networks and Operating Systems
Name of the Student
Name of the University
Author Note

1COMPUTER NETWORKS AND OPERATING SYSTEMS
Table of Contents
Introduction................................................................................................................................2
Applications of consensus protocols for unreliable networks....................................................2
Challenges presented by unreliable networks............................................................................3
Role of consensus protocols to solve these problems................................................................4
Critical Analysis.........................................................................................................................5
Conclusion..................................................................................................................................6
Reference....................................................................................................................................7
Appendix....................................................................................................................................8

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Introduction
The prime determination of this unit of the paper is to focus on the application of
security protocols due to the presence of the miss behaving agents which have a very
indifferent behaviour considering consensus network. There were huge complexities due to
security reasons in those networks, those networks usually deal with clock synchronisation,
motion co-ordination and co-operative estimation. The presence of the misbehaving agents
such as malicious agents such as Byzantine and faulty agents which are also known as the
non-colluding agents.
The security measures also help in detecting those faults in the first place. The prime
challenges related to those unreliable networks will be described in details in this paper. The
challenges will be described in such a way that it will help the readers of this document to
understand the reasons behind those challenges also (Rezaee and Abdollahi 2015). The paper
will also focus on the effectiveness of the consensus protocols which are actively used to
solve the problems related to those unreliable networks. This paper will provide the readers
with an idea about the impact of reliability on an operating system as most of the times the
system has some faulty components.
Applications of consensus protocols for unreliable networks
The challenges related to the consensus problems are a major issue in most of the
distributed systems these days. Stable results are not obtained from the fault free processors.
Dealing with these consensus problems is a must as they are very much influence from the
faulty components. The foremost problems related with the unreliable networks are the clock
synchronisation problem, agreeing on the value of the replicated sensor, finding the location
of the replicated file in the distributed systems and the transaction problems.
Reliability of a system is a very basic issue of every distributed computing systems
(Bae, Lim and Ahn 2017). As a huge number of data are processed in the computing systems,
there are different applications of consensus in those systems.
The prime applications of consensus protocols for the unreliable networks are as followings:
Transaction: It is one of the chief purposes of the consensus networks. The database of every
system is designed and built in such a way so that it can store and execute different types of
data irrespective of its design (Zheng and Wang 2016). So committing or saving the

3COMPUTER NETWORKS AND OPERATING SYSTEMS
transactions in the database is a very important very important application of consensus in
reliable networks.
Leaders: Election of the leaders in a distributed system is the other important application of
consensus in unreliable networks. The election of the leaders is initiated after the task is
underway. Communications of the networking nodes are very important in every distributed
system for the selection of the leaders (Hong et al. 2018). The nodes compare each other
specification and identities, the nodes with the highest identity is selected as the leader. All
the processors of the unreliable network know who their leader is and the also the features
provided by the leader to the nodes.
State Machine Replication: This one of the most important applications of consensus is the
state machine replication. Implementation of a fault tolerance service is attained with the
extensive use of the replicating servers. The design replication management protocol can be
understood with the help of the state machine replication. The unreliable network having
more than one server and operations are the main areas of expertise of this replication
approach.
Atomic broadcasts: Most of the distributed computing systems all the correct
processes receive a same set of messages with the help of a broadcast known as the atomic
broadcast. The application of the atomic broadcasts does not have any kind of side effect.
The validations of the messages which are sent from one location to another are done with the
help of the atomic broadcasts (Li, Wang and Li 2017). The atomic broadcast makes sure that
if one of the correct participants receives a message then all the participants can receive that
message. The integrity of those messages are also maintained with the help of this total order
broadcast. The order of the messages is also managed with the help of atomic broadcast in
unreliable networks.
Challenges presented by unreliable networks
The main challenge of the unreliable network is the delivery of the data in the desired
locations. The alteration and maintenance of the integrity of the data are the other important
challenges of these unreliable networks. Security dilemma is the other type of challenge
related to the unreliable networks. The ineffective communication processes considering
those messages are the other type of challenges related to the unreliable network (Chou et al.

4COMPUTER NETWORKS AND OPERATING SYSTEMS
2018). Increasing number of external threats in the form of hacking is the other type of
challenge related to the computer networks.
The consensus protocols are designed and implemented by experienced IT
professional in such a way that it is very much reliable to apply them in the unreliable
networks. The implementation of the consensus protocols is extremely costly in nature in
term of the computing resources and time. The validation of the blocks is done in a more
efficient manner with the help of the consulting protocols. The working mechanism of the
consensus protocols varies depending upon the block chain which is helpful in validating the
blocks. The consensus protocols are found in different categories and this method is very
much efficient and effective for security purposes in the unreliable computer networks.
The consensus protocols are the most important aspect of block chain technology.
The different networking systems which are connected in a distributed network are secured
from the different threats with the help of the consensus protocols. The nodes of the network
can agree with the help of the same state of a block chain making the network a self-auditing
echo system. The consensus protocols allow the block chain to be updated so that it can deal
with all the updates threats coming from the crackers as well as the hackers. Every participant
associated with the networking system is secured with the help of the consensus protocols. If
there are issues in any of the part of an unreliable network block chain system which
designed in such a way that the rest of the system is unaffected by it. The network reliability
issues are the biggest challenge of every business organisations. Reliable networking systems
are a must for every organisation to provide the desired products and services.
Role of consensus protocols to solve these problems
There are different techniques by which the challenges related to the unreliable
networks can be solved purposefully such as the internet content filters, proxy servers and
firewalls. The security of the data is often compromised with the help of these challenges. On
top of that, the hackers and the crackers play a huge role in these unreliable networks in spite
of strong data encryption technique. The extensive development in the field of networking
technology has led to the increase of connectivity and security issues also. The legal
liabilities are the other type of challenge related to the network security. The privacy
challenge is the most essential among all of the discussed challenges as the importance of
data which are transmitted from one location to another is increasing every day.

5COMPUTER NETWORKS AND OPERATING SYSTEMS
The co-ordination of the modes is done with the help of the data consistency, updating
the propagation of the data, considering the consistent global states, effective group
communication, distributed consensus and quorum consensus (Binetti et al. 2014). Even a
single type of faulty process has the ability to solve the challenges of the unreliable network.
Fault making is defined as a type of technique by which the complexities associated with the
processes can be effectively reduced. The failure detectors are the other type of security
measure in the unreliable networks.
The protocol rules of the consensus help in validating the blocks and the transactions
associated with it. Every single data value is made to follow the specific set of rules which
are followed in every distributed network. When the nodes of the network are failing or in the
unreliable connections the consensus rules can work unanimously. The block chain
technology sometimes goes through critical stages known as the double spend which can be
effectively avoided with the help of the consensus protocols. Incentives and rewards are
provided to the participants of the unreliable network for protecting the mechanism of the
distributed systems where they are integrated. Tokens and cryptocurrencies are the different
forms of incentives which are provided to each of the participants these are the most
motivating factors for each of the participants (Gao et al. 2016). The digital currencies are
used for maintaining a complete history of the transactions of users at any point of time or the
entire block chain process as a whole.
Critical Analysis
The author of this resource helps in identifying the issues related to the different
applications of the consensus protocols such as the involvement of the external threats in the
transactions, ineffective selection of the leaders with low specifications, issues related to the
state machine replication, incorrect validations of the atomic broadcasts.
Other writers have a completely different approach regarding this issue. There is a
completely different opinion about the different discussed applications of consensus
protocols. There are different issues related with those application so these uses also have
certain limitations associated with them (Gao, Cui and Chen 2017). The different types of
data collected from various sources help in identifying the issues related to the discussed
applications of consensus protocols. Based on the research done with the help of the practical
practitioners it can be concluded that the issues and challenges related with the discussed

6COMPUTER NETWORKS AND OPERATING SYSTEMS
applications of consensus protocols should be minimized to a significant extent so that the
desired security measures are considered in an unreliable network.
The discussed challenges of the unreliable network can also be evaluated from a
different perspective as well. There will be challenges related to the techniques which are
actively used to cope up with the challenges of consensus protocols. According to numerous
resources, it was known that there are different types of complexities associated with internet
content filters, proxy servers and firewalls. Blockage of wrong sites and contents are one of
the most important drawbacks of the internet content filters. Some of the authors stressed on
the accidental access to other sites as one of the major drawbacks of the content filters. The
survey helps in understanding the compatibility issues and the issues of data theft issues of
the proxy servers with the help of the TLS and SSL encrypted connections (Yu and Long
2015). Further studies help in understanding the limitations of the firewall as it cannot save
the systems from the internal threats it can only block the external threats from entering the
system.
Based on the above discussions of different authors it can be stated that that the
challenges related to the unreliable networks can be purposefully solved with the help of the
techniqies such as internet content filters, firewalls and the proxy servers. The blockage of the
websites is also a preventive step against the challenges of the unreliable networks. There are
drawbacks in those preventive steps which are needed to be minimised so that the efficiencies
of those techniques can be maintained.
Conclusion
From the above paper, it can be concluded that there are different types of limitations
associated with the application of consensus protocols for the unreliable networks such as the
cracking and the hacking activity of the cybercriminals who may have a role in the
transaction processes. Unprofessional database design may lead to many other types of
security issues as well. Inefficient election of the leaders is the other disadvantage of the
application of consensus in unreliable network.
There are compatibility issues regarding the replication of the servers in a computer
system as well. The prime challenges of the unreliable networks are also discussed in this
paper such as the inefficient delivery of data to the desired locations. Maintenance of the
alteration and integrity of the data are the other types of limitations of these unreliable

7COMPUTER NETWORKS AND OPERATING SYSTEMS
networks. The implementation of the consensus protocols in unreliable network is also very
costly in nature so effective planning is strictly required so that the effectiveness of the
protocol is maintained. The proxy servers, internet content filters and the firewalls can be
successfully used to solve the challenges related to the consensus protocols. It can be also
understood that there are numerous issues related with the application of consensus protocols
as well such as the blockage of website due to the internet content filters and data theft issues
due to the proxy servers and restricted security issues of firewall.

8COMPUTER NETWORKS AND OPERATING SYSTEMS
Reference
Bae, Y.B., Lim, Y.H. and Ahn, H.S., 2017, March. Edge deletion algorithm for minimally
rigid graph using consensus protocols. In Industrial Technology (ICIT), 2017 IEEE
International Conference on (pp. 779-784). IEEE.
Binetti, G., Davoudi, A., Lewis, F.L., Naso, D. and Turchiano, B., 2014. Distributed
consensus-based economic dispatch with transmission losses. IEEE Transactions on Power
Systems, 29(4), pp.1711-1720.
Chou, C.N., Lin, Y.J., Chen, R., Chang, H.Y., Tu, I. and Liao, S.W., 2018. Personalized
Difficulty Adjustment for Countering the Double-Spending Attack in Proof-of-Work
Consensus Protocols. arXiv preprint arXiv:1807.02933.
Gao, L., Cui, Y. and Chen, W., 2017. Admissible consensus for descriptor multi-agent
systems via distributed observer-based protocols. Journal of the Franklin Institute, 354(1),
pp.257-276.
Gao, L., Cui, Y., Chen, W. and Chen, W., 2016. Leader-following consensus for discrete-
time descriptor multi-agent systems with observer-based protocols. Transactions of the
Institute of Measurement and Control, 38(11), pp.1353-1364.
Hong, H., Yu, W., Fu, J. and Yu, X., 2018. A novel class of distributed fixed-time consensus
protocols for second-order nonlinear and disturbed multi-agent systems. IEEE Transactions
on Network Science and Engineering.
Li, G., Wang, X. and Li, S., 2017. Distributed composite output consensus protocols of
higher-order multi-agent systems subject to mismatched disturbances. IET Control Theory &
Applications, 11(8), pp.1162-1172.

9COMPUTER NETWORKS AND OPERATING SYSTEMS
Rezaee, H. and Abdollahi, F., 2015. Average consensus over high-order multiagent systems.
IEEE Transactions on Automatic Control, 60(11), pp.3047-3052.
Yu, S. and Long, X., 2015. Finite-time consensus for second-order multi-agent systems with
disturbances by integral sliding mode. Automatica, 54, pp.158-165.
Zheng, Y. and Wang, L., 2016. Consensus of switched multiagent systems. IEEE
Transactions on Circuits and Systems II: Express Briefs, 63(3), pp.314-318.

10COMPUTER NETWORKS AND OPERATING SYSTEMS
Appendix
Number Resource Reason for selection
1 Mushi, M., Murphy-Hill, E.
and Dutta, R., 2015, March.
The human factor: A
challenge for network
reliability design. In Design
of Reliable Communication
Networks (DRCN), 2015 11th
International Conference on
the (pp. 115-118). IEEE.
The challenges related to the
unreal network are focused in
this paper.
2 Jain, A., Network Security-
The Biggest Challenge in
Communication.
The network security
challenges are discussed in this
paper.
3 Wang, Y., Song, Y., Krstic,
M. and Wen, C., 2016. Fault-
tolerant finite time consensus
for multiple uncertain
nonlinear mechanical systems
under single-way directed
communication interactions
and actuation failures.
Automatica, 63, pp.374-383.
The failures of the fault
tolerance systems which works
on the consensus protocols are
discussed in this resource.
4 Ongaro, D. and Ousterhout,
J.K., 2014, June. In search of
an understandable consensus
algorithm. In USENIX
Annual Technical Conference
(pp. 305-319).
The algorithm of the consensus
protocols is described in this
paper.
5 Li, Z., Wen, G., Duan, Z. and
Ren, W., 2015. Designing
fully distributed consensus
protocols for linear multi-
agent systems with directed
graphs. IEEE Transactions
on Automatic Control, 60(4),
pp.1152-1157.
The distributed consensus
protocols for linear multi agent
systems which gives an idea
about the working principals of
the consensus protocols.
6 Zuo, Z. and Tie, L., 2014. A
new class of finite-time
nonlinear consensus
protocols for multi-agent
systems. International
Journal of Control, 87(2),
pp.363-370.
This resource helps in the
understanding different aspects
of nonlinear consensus
protocols for different systems.

11COMPUTER NETWORKS AND OPERATING SYSTEMS
7 El Chamie, M., Neglia, G.
and Avrachenkov, K., 2015.
Distributed weight selection
in consensus protocols by
Schatten norm minimization.
IEEE Transactions on
Automatic Control, 60(5),
pp.1350-1355.
The resource helps in
determining the impact of
consensus protocols in the
automatic transactions.
8 Carvalho, C., Porto, D.,
Rodrigues, L., Bravo, M. and
Bessani, A., 2018. Dynamic
Adaptation of Byzantine
Consensus Protocols.
The impact of the adaptation of
byzantine in the consensus
protocols are described in this
paper.
9 Park, M.J., Kwon, O.M. and
Seuret, A., 2017. Weighted
consensus protocols design
based on network centrality
for multi-agent systems with
sampled-data. IEEE
Transactions on Automatic
Control, 62(6), pp.2916-2922.
The reason behind selecting
this resource is that the
effectiveness of the design can
be well understood with the
help of this resource.
10 Cachin, C. and Vukolić, M.,
2017. Blockchains consensus
protocols in the wild. arXiv
preprint arXiv:1707.01873.
The reason behind selecting
this resource is that it gives an
idea about the impact of block
chain technology in consensus
protocols.