RPC, Java RMI and Marshaling

What is the purpose of the marshaling procedure?

to encode application layer structures in an external form

What is a gossip protocol?

A protocol where peers randomly exchange messages to achieve, for example, unreliable multicast.

What is meant by time uncoupling in a communication framework?

Sender and receiver need not be active at the same time.

What is meant by space uncoupling in a communication framework?

A sender does not need to know the name or identifier of the receiver.

What is meant by an idempotent operation?

n operation that can be performed several times with the same effect as being performed once.

What is meant by causal ordering in a communication framework?

If a client is delivered two messages m1 and m2, then m1 could not have been sent by someone after having being delivered m2.

How are arguments passed in Java RMI?

remote objects as reference, all other as copies

Which invocation semantic is provided by Java RMI?

at most once

What level of transparency is provided by method invocation in Java RMI?

access and location transparency

If a RPC call with at least once semantics fails, we know that

the call might have been executed at least once

What is given by at least once RPC semantics?

even if a failure occurs the call has been invoked at least once

Why is a remote object passed as a reference and not as a copy in Java RMI?

the object contains a mutable state that should not be duplicated

Can we implement a RPC system with exactly-once semantics in an asynchronous system with non-failing nodes but unreliable networks?

no, we can only achieve at-most-once or at-least-once but not both

What is the difference when an error is reported for an at-least-once and at-most-once remote procedure call?

in the at-least-once case, the call could have been executed more than once