CHAPTER 2
Network Models
Solutions to Review Questions and Exercises
Review Questions
1-List the layers of the internet model?
1. The Internet model, as discussed in this chapter, include physical, data link, network,transport, and application layers.
2-Which layer of the internet model is
the user support layer?
The application layer supports the
user.
3-What is peer to peer process?
Peer-to-peer processes are processes on two or more devices communicating at a
same layer
4-What are headers and trailers how are
they added and removed?
Headers and trailers are control data added at the beginning and the end of each
data unit at each layer of the sender and removed at the corresponding layers of the
receiver. They provide source and destination addresses, synchronization points,
information for error detection, etc.
5-What are the responsibility of the Data
link layer in the internet model?
The data link layer is responsible for
a. framing data bits
b. providing the
physical addresses of the sender/receiver
c. data rate control
d. detection and
correction of damaged and lost frames
6-What are the responsibility of
Transport layer in the internet model? .
The transport layer oversees the process-to-process delivery of the entire message.
The transport layer oversees the
process-to-process delivery of the entire message.
It is responsible for
a. dividing the message
into manageable segments
b. reassembling it at
the destination
c. flow and error
control
7-Name some services provided by the
application layer in the internet model?
The application layer services include file transfer, remote access, shared database
management, and mail services.
Exercises
8-How are OSI and ISO related to each
other? .
The International Standards Organization, or the International Organization of
Standards, (ISO) is a multinational body dedicated to worldwide agreement on
international standards. An ISO standard that covers all aspects of network communications
is the Open Systems Interconnection (OSI) model.
9
a. Reliable process-to-process delivery: transport layer
b. Route selection: network layer
c. Defining frames: data link layer
d. Providing user services: application layer
e. Transmission of bits across the medium: physical layer
10
a. Format and code conversion services: presentation layer
b. Establishing, managing, and terminating sessions: session layer
c. Ensuring reliable transmission of data: data link and transport layers
d. Log-in and log-out procedures: session layer
e. Providing independence from different data representation: presentation layer
21. See Figure 2.1.
23. Before using the destination address in an intermediate or the destination node, the
packet goes through error checking that may help the node find the corruption
(with a high probability) and discard the packet. Normally the upper layer protocol
will inform the source to resend the packet.
25. The errors between the nodes can be detected by the data link layer control, but the
error at the node (between input port and output port) of the node cannot be
detected by the data link layer.
