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CS6250 Computer Networks Exam Questions with Verified Correct Answer
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CS6250 Computer Networks Exam Questions with Verified Correct Answer
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CS6250 Computer Networks Exam Questions withVerified Correct Answer
What are advantages and disadvantages of a layered architecture? -
ANSWERSeparation of concerns among logical layers promotes flexibility, scalibility,
and maintainability. Multiple applications can reuse the components. It enables teams to
work on different parts with minimal dependencies on other teams
What are the similarities of the OSI model and five-layered Internet model? -
ANSWERThey are both based on layered architecture.
The are comparable to each other - see image 1
Both are networking standards
What are the differences of the OSI model and five-layered Internet model? -
ANSWEROSI is a generic model based on the functions of each layer. TCP is a
protocol oriented standard.
OSI uses 3 upper layers (application, presentation, and session) while TCP just uses
application.
Likewise, OSI uses 2 Lower layers (Physical and DataLink) while TCP just uses Link
What is a socket? - ANSWERA socket is one endpoint of a two-way communication link
between two programs running on the network.
A socket is bound to a port number so that the TCP layer can identify the application
that data is destined to be sent to.
Physical Layer - ANSWERThe lowest, or first, layer of the OSI model. Protocols in this
layer generate and detect signals so as to transmit and receive data over a network
medium. These protocols also set the data transmission rate and monitor data error
rates, but do not provide error correction.
The lowest layer of the OSI Model is concerned with electrically or optically transmitting
raw unstructured data bits across the network from the physical layer of the sending
device to the physical layer of the receiving device. It can include specifications such as
voltages, pin layout, cabling, and radio frequencies. At the physical layer, one might find
"physical" resources such as network hubs, cabling, repeaters, network adapters or
modems.
,OSI Data Link Layer - ANSWERAt the data link layer, directly connected nodes are
used to perform node-to-node data transfer where data is packaged into frames. The
data link layer also corrects errors that may have occurred at the physical layer.
The data link layer encompasses two sub-layers of its own. The first, media access
control (MAC), provides flow control and multiplexing for device transmissions over a
network. The second, the logical link control (LLC), provides flow and error control over
the physical medium as well as identifies line protocols.
OSI Network Layer - ANSWERThe network layer is responsible for receiving frames
from the data link layer, and delivering them to their intended destinations among based
on the addresses contained inside the frame. The network layer finds the destination by
using logical addresses, such as IP (internet protocol). At this layer, routers are a crucial
component used to quite literally route information where it needs to go between
networks.
OSI Transport Layer - ANSWERThe transport layer manages the delivery and error
checking of data packets. It regulates the size, sequencing, and ultimately the transfer
of data between systems and hosts. One of the most common examples of the
transport layer is TCP or the Transmission Control Protocol.
OSI Session Layer - ANSWERThe session layer controls the conversations between
different computers. A session or connection between machines is set up, managed,
and termined at layer 5. Session layer services also include authentication and
reconnections.
OSI Presentation Layer - ANSWERThe presentation layer formats or translates data for
the application layer based on the syntax or semantics that the application accepts.
Because of this, it at times also called the syntax layer. This layer can also handle the
encryption and decryption required by the application layer.
OSI Application Layer - ANSWERAt this layer, both the end user and the application
layer interact directly with the software application. This layer sees network services
provided to end-user applications such as a web browser or Office 365. The application
layer identifies communication partners, resource availability, and synchronizes
communication.
5 Layer Internet Model - Application Layer - ANSWERAs you might have guessed, the
Application layer is where applications requiring network communications live.
Examples of these applications include email clients and web browsers. These
applications use the Transport Layer to send requests to connect to remote hosts.
5 Layer Internet Model - Transport Layer - ANSWERThe Transport layer establishes the
connection between applications running on different hosts. It uses TCP for reliable
connections and UDP for fast connections. It keeps track of the processes running in
, the applications above it by assigning port numbers to them and uses the Network layer
to access the TCP/IP network.
5 Layer Internet Model - Network Layer - ANSWERThe Network layer is responsible for
creating the packets that move across the network. It uses IP addresses to identify the
packet's source and destination.
5 Layer Internet Model - Data Link Layer - ANSWERThe Data Link layer is responsible
for creating the frames that move across the network. These frames encapsulate the
packets and use MAC addresses to identify the source and destination.
5 Layer Internet Model - Physical Layer - ANSWERThe Physical layer encodes and
decodes the bits found in a frame and includes the transceiver that drives and receives
the signals on the network.
What is encapsulation, and how is it used in a layered model? - ANSWERIn networking
model, the terms encapsulation and de-encapsulation refer to a process in which
protocol information is added to the data and removed from the data when it passes
through the layers.
Protocol information can be added before and after the data. If information is added
before the data, it is known as header. If information is added after the data, it is known
as trailer.
What is the end-to-end (e2e) principle? - ANSWERWhen a function has to be supported
in a networked system, the designer often asks if it should be implemented at the end
systems; or should it be implemented within the communication subsystem that
interconnects all the end systems. The end-to-end argument or principle states that it's
proper to implement the function in the end systems. The communication system itself
may provide a partial implementation but only as a performance enhancement.
The architecture and growth of the Internet was shaped by the end-to-end principle. It
allowed us to keep the Internet simple and add features quickly to end systems. The
principle enabled innovation.
End to End Principle Example - ANSWERAn example of the end-to-end principle is that
of an arbitrarily reliable file transfer between two endpoints in a distributed network of a
varying, nontrivial size:[3] The only way two endpoints can obtain a completely reliable
transfer is by transmitting and acknowledging a checksum for the entire data stream; in
such a setting, lesser checksum and acknowledgment (ACK/NACK) protocols are
justified only for the purpose of optimizing performance - they are useful to the vast
majority of clients, but are not enough to fulfill the reliability requirement of this particular
application. A thorough checksum is hence best done at the endpoints, and the network
maintains a relatively low level of complexity and reasonable performance for all clients
What is the EvoArch model? - ANSWERan hourglass model that consists of six protocol
and application layers that originate from a single bubble - IPv4
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