Chapter 3

Where is transport-layer functionality primarily implemented?

• Transport layer functions are implemented primarily at the hosts at the “edge” of the network.

• Transport layer functions are implemented primarily at each end of a physical link connecting one host/router/switch to another one host/router/switch.

• Transport layer functions are implemented primarily at the routers and switches in the network.

True or False: The transport layer provides for host-to-host delivery service?

• True

• False

  Check all of the services below that are provided by the TCP protocol.

• Reliable data delivery.

• A byte stream abstraction, that does not preserve boundaries between message data sent in different socket send calls at the sender.

• In-order data delivery

• A congestion control service to ensure that multiple senders do not overload network links.

• A flow-control service that ensures that a sender will not send at such a high rate so as to overflow receiving host buffers.

  Check all of the services below that are provided by the UDP protocol.

• A byte stream abstraction

• Reliable data delivery.

• A guarantee on the maximum amount of time needed to deliver data from sender to receiver.

• A guarantee on the minimum amount of throughput that will be provided between sender and receiver.

• A message abstraction, that preserves boundaries between message data sent in different socket send calls at the sender.

What is meant by transport-layer demultiplexing?

• Taking data from one socket (one of possibly many sockets), encapsulating a data chuck with header information – thereby creating a transport layer segment – and eventually passing this segment to the network layer.

• Receiving a transport-layer segment from the network layer, extracting the payload (data) and delivering the data to the correct socket.

• Receiving a transport-layer segment from the network layer, extracting the payload, determining the destination IP address for the data, and then passing the segment and the IP address back down to the network layer.

• Taking data from multiple sockets, all associated with the same destination IP address, adding destination port numbers to each piece of data, and then concatenating these to form a transport-layer segment, and eventually passing this segment to the network layer.

What is meant by transport-layer multiplexing?

• Taking data from one socket (one of possibly many sockets), encapsulating a data chuck with header information – thereby creating a transport layer segment – and eventually passing this segment to the network layer.

• Receiving a transport-layer segment from the network layer, extracting the payload (data) and delivering the data to the correct socket.

• Receiving a transport-layer segment from the network layer, extracting the payload, determining the destination IP address for the data, and then passing the segment and the IP address back down to the network layer.

• Taking data from multiple sockets, all associated with the same destination IP address, adding destination port numbers to each piece of data, and then concatenating these to form a transport-layer segment, and eventually passing this segment to the network layer.

True or False:  When multiple UDP clients send UDP segments to the same destination port number at a receiving host, those segments (from different senders) will always be directed to the same socket at the receiving host.

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• True

• False

True or False:  When multiple TCP clients send TCP segments to the same destination port number at a receiving host, those segments (from different senders) will always be directed to the same socket at the receiving host.

 

• True

• False

True or False:  It is possible for two UDP segments  to be sent from the same socket with source port 5723 at a server to two different clients.

• True

• False

True or False:  It is possible for two TCP segments with source port 80 to be sent by the sending host to different clients.

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• True

• False