计算机分布式系统代写 COMP90015 Distributed Systems

COMP90015 Distributed Systems: Principles and Paradigms

计算机分布式系统代写 What are the differences between the message queue paradigm and the publish/subscribe paradigm? Give an example application where

Q.1.  计算机分布式系统代写

(a) [5 marks] Consider a non-distributed application that allows a user to conduct a long-running simulation, with the ability to monitor and control the simulation using a graphical user (GUI) interface. The GUI interface displays a large number of simulation outputs in real-time. Now consider the same application that has been split into two processes: a server process that runs the simulation, and a GUI process that allows user monitoring and control. This is now a distributed application. Give three reasons for and two reasons against the use of a distributed application with respect to this example. Make sure your reasons are all distinctly different.

(b) [5 marks] Explain what is meant by eventual consistency in a distributed system. You may give an example application to aid your answer. Give your reasons for and against adopting eventual consistency in a distributed system.

Q.2.

[5 marks] For each of the following architectural designs, provide a definition and give a reason for and a reason against the use of the design. Draw a diagram to
illustrate the architecture.
(a) Client/Server
(b) Peer-to-Peer
(c) Multi-server
(d) Proxy server
(e) Thin-client

Q.3.  计算机分布式系统代写

[5 marks] In the first project, a minimum connection time interval was used, whereby connections from a given IP address were only allowed to continue if there
had been no connection within the last connection time interval. What purpose does this serve? What drawbacks or weaknesses does it have? Is there a better way
to achieve the same functionality? If yes, explain, if no give a reason.

Q.4.

(a) [5 marks] Suppose that a client creates a TCP Socket to a server, sends a command, and waits for a response. However the server has failed internally and does not respond, though the connection remains open. What can be done by the client to overcome this? Critically explain your answer and include discussion concerning relevant distributed system challenges.

(b) [5 marks] Explain what is meant by a remote procedure call or RPC. Discuss the aspects of implementing an RPC middleware such as Sun RPC. Draw a diagram to show the architectural components of the implementation.

Q.5.  计算机分布式系统代写

(a) [5 marks] What are the differences between the message queue paradigm and the publish/subscribe paradigm? Give an example application where the message queue paradigm would be the more appropriate choice over publish/subscribe and say why

(b) [5 marks] What is meant by the term overlay network in distributed systems? What is a benefit of using an overlay network? Give an example application that could benefit and draw a diagram.
(a) [4 marks] What is the purpose of cipher block chaining? Describe a technique that achieves cypher block chaining.
(b) [3 marks] List and briefly explain three worst-case assumptions when designing a secure system.
(c) [3 marks] Explain what is a digital certificate, including what is the basic technique used to create a digital certificate, and what is a certificate chain.

Q.6.

(a) [3 marks] Explain what is meant by process migration. Explain two major complications with process migration.
(b) [2 marks] What is the difference between a static location policy and a dynamic location policy? Give an example static policy and an example dynamic policy.
(c) [2 marks] With respect to decentralized load balancing, what is the difference between a sender-initiated and a receiver-initiated policy? Under what load
conditions is the former more efficient?

Q.7.  计算机分布式系统代写

A typical flat file service interface is shown below:

Read(UFID, i, n) → Data Reads up to n items from position i in the file.
Write(UFID, i, Data) Writes the data starting at position i in the file. The file is extended if necessary.
Create() → UFID Creates a new file of length 0 and returns a UFID for it.
Delete(UFID) Removes the file from the file store.
GetAttributes(UFID) → Attr Returns the file attributes for the file.
SetAttributes(UFID,Attr) Sets the file attributes.

(a) [1 marks] What is typically done to ensure that a UFID is unique across different file servers?
(b) [1 marks] Why does the interface not provide an Open(. . . ) primitive?
(c) [1 marks] Which of the primitives of the interface, if any, are not idempotent?

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