Distributed systems

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A. Practices on Entity Naming in Distributed Systems

1. Entity Naming Preliminaries

a) Can an identifier used in naming refer to more than one entity in a distributed system? Why

or why not?

b) Why do you think for efficient and wide application in distributed system we need names

to be location independent? Give specific examples in your explanations.

c) Briefly explain what information is necessary for mounting to be possible in a distributed

system. Can any workstation mount any file in a distributed system? Why or why not? What

are the advantages of mounting in case of low budgets?

d) Why do you think merging of different name spaces can cause scalability problems? Are

there situations where scalability would not be a problem? Explain your answer.

e) Briefly differentiate between lazy and (immediate) eager update propagation. How can they

be compared to delayed-write and write-through policy in implementation? Which

situations would they be good?

2. Replication in Distributed Environment

a) Why do you think the number of replicas for global layer are many?

b) Can you think of a commercial example of such in the internet domain that you are familiar

with? What are the problems for users of the services?

c) Do you think caching in the global layer replicas can be a problem in such a situation? (Hint:

Think Consistency!). What is the potential solution?

d) Under what circumstances does the iterative name resolution process become a better

process than recursive name resolution?

e) Under what circumstances does the iterative name resolution process become a better

process than recursive name resolution? How can you know for sure whether to use

iterative or recursion resolution for your distributed environment?

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3. Pointers in Distributed Environment

a) Why should a designer to a distributed environment be wary of using pointers for tracing

entities? Any solutions to the potential problems?

b) How does the heterogeneous environment handle the use of pointers? Is it scalable?

c) In the hierarchical approach for locating pointers, does the depth of really hierarchy matter?

d) How can one obtain the optimum working scenario for the hierarchy organization for the

distributed environment?

4. Locating Entities in a Distributed Environment

a) What kind of naming services do you know? Why do distributed systems need this

function?

b) Why is it that broadcasting (or multicasting) can cause scalability problems? Hint:

Performance problems and are susceptible to broken links.

c) What would be a better approach to support mobile entities in large-scale networks? Any

precautions in this application format.

d) What are the drawbacks of home-based approach in large-scale networks? Hint:

Communication latency and fixed home location.

e) How does name caching improve help a name service’s availability? Hint: Names