1.Chapter 1, Question13: Describe the five layers in the Internet network model and what they do.
Physical Layer : used by application program , transfer a series of electrical, radio, or light signals through the circuit.
Data Link Layer : It performs the same three functions as the data link layer in the OSI model. First, it controls the physical layer by deciding when to transmit messages over the media. Second, it formats the messages by indicating where they start and end. Third, it detects and may correct any errors that have occurred
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First, it is responsible for linking the application layer software to the network and establishing end-to-end connections between the sender and receiver when such connections are needed. Second, it is responsible for breaking long messages into several smaller messages to make them easier to transmit and then recombining the smaller messages back into the original larger message at the receiving end. The transport layer can also detect lost messages and request that they be resent.
Application Layer : It is the application software used by the network user and includes much of what the OSI model contains in the application, presentation, and session layers. It is the user’s access to the network. By using the application software, the user defines what messages are sent over the network.
2.Chapter 1,Queation 26:How many bits (not bytes) are there in a 10 page text document? Hint: There are approximately 350 words on a double-spaced page.
Use the following assumptions:
* There are 350 words on a page
* There are 6 characters per word
* There are 8 bits per character (because of ASCII coding)
Because there are 8 bits per character (because of ASCII coding), so there are 6×8=48 bits per word. Because there are 350 words on a page, so there are 48×350=16800 bits per page.
There are 16800×10=168000 bits in a 10 page text document.