Serving applications - Multiple Choices Questions - [CNP3] Computer Networking : Principles, Protocols and Practice

שאלה 1: The transport services

The services play an important role in computer networks since they define what the user can really expect. Selection all the correct affirmations about the connectionless network service ?

The connectionless network service may never deliver some SDUs to their destination.

The connectionless network service may deliver the same SDU several times to a given destination.

The connectionless network will always deliver SDUs in order at their destination.

The connectionless network service will never deliver twice the same SDU to a given destination.

The connectionless network service can transfer SDUs of limited size

The connectionless network service may deliver corrupted SDUs at their destination

שאלה 2: The connection-oriented service: user interactions

The connection-oriented service is perhaps the most widely used transport service. The interactions between the user of the service and the underlying protocol can be represented as the exchange of various primitives. Considering the interactions between a user of the connection-oriented transport service and its provider, which of the following affirmations are correct? Select all the correct ones.

A Connect.request primitive issued by a user can be followed by a Disconnect.indication issued by the service provider.

A service provider may issue a Disconnect.indication primitive on an established connection at any time.

A user that has initiated a connection cannot issue a Data.request before having received a Connect.confirm primitive.

The service provider issues a Connect.indication primitive to indicate that it has received a connection establishment attempt.

To confirm the establishment of a connection, a user responds to a Connect.request primitive by issuing a Connect.response primitive.

A Connect.request primitive issued by a user is always followed by a Connect.confirm issued by the service provider.

To refuse the establishment of a connection, a user responds to a Connect.indication primitive with a Disconnect.request primitive.

A user that has received a Connect.indication primitive can immediately issue Data.request primitives to send data over the connection.

A user that has accepted a connection can issue a Data.request immediately after having issued the Connect.response primitive.

A Connect.request primitive is issued by the user to request the establishment of a connection.

שאלה 3: The connection-oriented transport service

Consider the connection-oriented transport service. Among the following affirmations about this service, select the ones that are correct.

A user may issue a Data.request after having received a graceful Disconnect.indication.

A transport service provider may itself issue a Disconnect.indication to gracefully terminate a connection.

When a user issues a graceful Disconnect.request, only one direction of transfer is closed.

An abrupt connection release may cause some SDUs to be corrupted.

A transport service provider may issue a Data.indication primitive to a user after having received a graceful Disconnect.request from this user.

With a message-mode service, each Data.request issued by one user will lead to a Data.indication at the other end.

A transport service provider may issue a Disconnect.indication at any time to terminate a connection.

An abrupt connection release may cause some SDUs to be discarded.

שאלה 4: The network layer

Which of the following affirmations correspond to the behaviour of the network layer ? Select all the correct ones.

The network layer may deliver the same packet several times to a given destination.

The network layer may loose packets.

The network layer will never deliver a given packet twice.

The network layer may modify the content of packets.

שאלה 5: Connectionless transport

Which of the following mechanisms are likely to be used inside a protocol that provides the unreliable connectionless transport service running on top of an unreliable connectionless network layer? Select all the applicable mechanisms.

A connection establishment mechanism.

Port numbers to identify the communicating applications.

Go-back-n.

A CRC to detect transmission errors.

Selective repeat.

A checksum to detect transmission errors.

שאלה 6: The three-way handshake

The three-way handshake allows successfully negotiating the establishment of a transport connection. Among the following time-sequence diagrams, which is the one that corresponds to a valid three-way handshake ?

שאלה 7: The three-way handshake: possible scenarios

The three-way handshake allows successfully negotiating the establishment of a transport connection. Consider a transport connection that begins which the exchange of two segments as shown in the figure below.

Consider what happens after the exchange of these two segments. Only one of the affirmations below is correct. Which one ?

At this stage, the connection is established and all CA segments that arrive should be considered as duplicate and discarded.

If Host B does not receive CA(seq=12345,ack=56789) after some time, it will retransmit CA(seq=56789,ack=12345).

If Host B receives again CR(seq=12345), it will discard the duplicate segment.

מועד הגשה	אין מועד הגשה
מגבלת הגשות	אין הגבלה
תגיות קטגוריה	transport

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