4. Transparency Goals Flashcards Preview

COMP18112 - Distributed Systems > 4. Transparency Goals > Flashcards

Flashcards in 4. Transparency Goals Deck (10)
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1
Q

What does transparency mean?

A

A process or interface functioning without the user being aware of its presence

2
Q

What are the standard set of transparencies?

A

Access: hiding how a resource is accessed
Location: hiding where a resource is located
Migration: hiding the fact that a resource may move location
Relocation: hiding the fact a resource may move to another location during use
Replication: Hiding the fact a resource is replicated
Concurrency: Hiding the fact a resource may be shared by several users
Failure: hiding the failure and recovery of a resource

3
Q

Why is transparency desirable?

A

Allows us to build DSs “as if” they were centralised. Or “as if” the axioms weren’t in force

4
Q

How do we achieve transparency of location?

A

Transport and internet protocols (DNS). Naming, addressing, connection and routing

5
Q

How do we achieve transparency of migration?

A

Dynamically update directories of hosts and routes.

6
Q

How do we achieve transparency of relocation?

A

The physical and link layers take care of handover from cell to cell. Transport and internet protocols are still in charge

7
Q

How do we achieve transparency of replication?

A

Transport and internet protocols are not enough here, distributed processors and resource managers need to schedule cleverly

8
Q

How do we achieve transparency of access?

A

Use interoperable standards XML, RDF etc. Compensate with wrappers and mappers to build mediator middleware.

9
Q

How do we achieve transparency of concurrency?

A

Resource/ process managers handle concurrent access using the following algorithms:
selecting a coordinator
clock synchronisation
joint decision making
May lead to issues such as deadlock and livelock.

10
Q

How do we achieve transparency of failure?

A

Sender can poll/ try again