Computer Networks-CS 6250 Exam2 Questions and
Answers Latest Versions (Complete and Accurate)
OSI Application Layer - ✔✔At 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 - ✔✔As 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 - ✔✔The 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 - ✔✔The 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 - ✔✔The 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 - ✔✔The 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? - ✔✔In 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? - ✔✔When 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 - ✔✔An 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? - ✔✔an hourglass model that consists of six protocol
and application layers that originate from a single bubble - IPv4
What are the ramifications of the hourglass shape of the internet - ✔✔
Repeater - ✔✔Physical Layer - A repeater operates at the physical layer. Its job is to regenerate
the signal over the same network before the signal becomes too weak or corrupted so as to extend
the length to which the signal can be transmitted over the same network. An important point to be
noted about repeaters is that they do not amplify the signal. When the
, signal becomes weak, they copy the signal bit by bit and regenerate it at the original strength.
It is a 2 port device.
Hub - ✔✔Physical Layer - A hub is basically a multiport repeater. A hub connects multiple
wires coming from different branches, for example, the connector in star topology which
connects different stations. Hubs cannot filter data, so data packets are sent to all connected
devices. In other words, collision domain of all hosts connected through Hub remains one.
Also, they do not have intelligence to find out best path for data packets which leads to
inefficiencies and wastage.
Bridge - ✔✔Data Link Layer - A bridge is a repeater, with add on the functionality of
filtering content by reading the MAC addresses of source and destination. It is also used for
interconnecting two LANs working on the same protocol. It has a single input and single
output port, thus making it a 2 port device.
Switch - ✔✔Data Link Layer - A switch is a multiport bridge with a buffer and a design that
can boost its efficiency(a large number of ports imply less traffic) and performance. A switch is
a data link layer device. The switch can perform error checking before forwarding data, that
makes it very efficient as it does not forward packets that have errors and forward good
packets selectively to correct port only. In other words, switch divides collision domain of
hosts, but broadcast domain remains same.
Router - ✔✔Network Layer - A router is a device like a switch that routes data packets
based on their IP addresses. Router is mainly a Network Layer device. Routers normally
connect LANs and WANs together and have a dynamically updating routing table based on
which they make decisions on routing the data packets. Router divide broadcast domains of
hosts connected through it.
What is a bridge, and how does it "learn" - ✔✔Data Link Layer Device -
bridge need to learn which computers are connected to which of its LAN interfaces. More
formally, it need to learn the set of source address that are received on each interface. The
source address of each received frame is recorded in the address table, together with the
port on which the frame was received. This is called learning
Answers Latest Versions (Complete and Accurate)
OSI Application Layer - ✔✔At 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 - ✔✔As 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 - ✔✔The 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 - ✔✔The 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 - ✔✔The 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 - ✔✔The 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? - ✔✔In 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? - ✔✔When 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 - ✔✔An 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? - ✔✔an hourglass model that consists of six protocol
and application layers that originate from a single bubble - IPv4
What are the ramifications of the hourglass shape of the internet - ✔✔
Repeater - ✔✔Physical Layer - A repeater operates at the physical layer. Its job is to regenerate
the signal over the same network before the signal becomes too weak or corrupted so as to extend
the length to which the signal can be transmitted over the same network. An important point to be
noted about repeaters is that they do not amplify the signal. When the
, signal becomes weak, they copy the signal bit by bit and regenerate it at the original strength.
It is a 2 port device.
Hub - ✔✔Physical Layer - A hub is basically a multiport repeater. A hub connects multiple
wires coming from different branches, for example, the connector in star topology which
connects different stations. Hubs cannot filter data, so data packets are sent to all connected
devices. In other words, collision domain of all hosts connected through Hub remains one.
Also, they do not have intelligence to find out best path for data packets which leads to
inefficiencies and wastage.
Bridge - ✔✔Data Link Layer - A bridge is a repeater, with add on the functionality of
filtering content by reading the MAC addresses of source and destination. It is also used for
interconnecting two LANs working on the same protocol. It has a single input and single
output port, thus making it a 2 port device.
Switch - ✔✔Data Link Layer - A switch is a multiport bridge with a buffer and a design that
can boost its efficiency(a large number of ports imply less traffic) and performance. A switch is
a data link layer device. The switch can perform error checking before forwarding data, that
makes it very efficient as it does not forward packets that have errors and forward good
packets selectively to correct port only. In other words, switch divides collision domain of
hosts, but broadcast domain remains same.
Router - ✔✔Network Layer - A router is a device like a switch that routes data packets
based on their IP addresses. Router is mainly a Network Layer device. Routers normally
connect LANs and WANs together and have a dynamically updating routing table based on
which they make decisions on routing the data packets. Router divide broadcast domains of
hosts connected through it.
What is a bridge, and how does it "learn" - ✔✔Data Link Layer Device -
bridge need to learn which computers are connected to which of its LAN interfaces. More
formally, it need to learn the set of source address that are received on each interface. The
source address of each received frame is recorded in the address table, together with the
port on which the frame was received. This is called learning
