Task 13. Find the answers to these questions in the text 11B.

Date: 2015-10-07; view: 623.

Task 12. Mark the following statements true or false.

Task 11. Fill in the blanks with the proper word from the text 11B.

1. The message is ____________into bits by the ________________layer.

2. The ___________ layer confirms the arrival of the packets, logs them in, and calculates the ____________ for each packet.

3. The incoming ___________ are recounted by the network layer for security and billing purposes.

4. The checksum is re-____________by the transport layer which also reassembles the message segments.

5. The parts of the message are held _______________the session layer _____________the message is complete. Then it sends the message to the next _______________________.

6. The message is compressed and ___________________ by the presentation layer.

7. The application layer converts the bits into __________________ characters, and ____________ the data to the correct application.

1. Most of the work that an application does to prepare a message for sending over a network is not seen by the user.

2. ASCII is always used to transmit data.

3. The encryption layer compresses the message.

4. The network layer keeps track of how many packets are in each message.

5. The network layer keeps a copy of each packet until it arrives at the next node undamaged.

6. Analogue signals are used on ordinary telephone lines.

7. When a message arrives at its destination, it passes through the same seven network communications layers as when it was sent, but in reverse order.

1. Into what units is data subdivided by the following layers?

a. transport layer

b. network layer

2. What is the purpose of a transmission checksum test?

3. How long does the data-link layer keep a copy of each packet?

4. What processes can be carried out at intermediate nodes?

5. Which network communications layer is described by each of the following statements?

a. Makes sure that the message is transmitted in a language that the receiving computer can understand

b. Protects the data being sent

d. Encodes and sends the packets

e. Supervises the transmission

f. The part of a communications process that a user sees

g. Starts communications and looks after communications among network nodes

h. Chooses a route for the message

i. Makes backup copies of the data if required

j. Confirms the checksum, then addresses and duplicates the packets