Exampromax - Stuvia US 2025/2026
1
CS6250 Computer Networks Exam 1 Questions
and Answers and Graded
What are advantages and disadvantages of a layered architecture?
Correct Answer
Each protocol layer offers different services. Some
advantages are scalability, flexibility, and ease of adding /
removing components making it easier for cost-effective
implementations. Disadvantages include: some layers
functionality depends on the information from the other
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layer and violates the goal of layer separation; one layer
Exampromax - Stuvia US
may duplicate lower layer functionalities; overhead both in
computation and in message headers caused by abstraction
barriers between layers.
What are the differences and similarities of the OSI model and five-layered
Internet model?
Correct Answer
The OSI model and the 5-layered Internet Model have
many of the same layers, with the difference being three of
the layers are combined in the 5-layered model. Specifically
the five-layer model combines the application,
presentation, and session layers from the OSI model into a
single application layer.
What are sockets?
Correct Answer
, Exampromax - Stuvia US 2025/2026
2
A network socket is a software structure within a network
node of a computer network that serves as an endpoint for
sending and receiving data across the network. The
structure and properties of a socket are defined by an
application programming interface (API) for the networking
architecture. Sockets are created only during the lifetime of
a process of an application running in the
node.https://en.wikipedia.org/wiki/Network_socket."A
process sends messages into, and receives messages from,
the network through a software interface called a socket.
Let's consider an analogy to help us understand processes
and sockets. A process is analogous to a house and its
© 2025 Assignment Expert
socket is analogous to its door....a socket is the interface
Exampromax - Stuvia US
between the application layer and the transport layer within
a host." - Kurose and Ross, 2.1
Describe each layer of the OSI model.
Correct Answer
Application layer: Service, Interface, Protocol. Ex: Turn on
your smartphone and look at the list of apps. (HTTP, SMTP,
FTP, DNS)
Presentation layer: Plays intermediate role of formatting the
information received from the layer below and delivering it
to the application layer. Ex: converting big endian to little
endian.
Session layer: Responsible for the mechanism that manages
the different transport streams that belong to the same
session between end-user and application process. Ex:
teleconference app, it is responsible for tying together
audio and video streaming.
, Exampromax - Stuvia US 2025/2026
3
Transport layer: Responsible for the end-to-end
communication between end hosts. 2 transport protocols,
TCP and UDP. TCP includes a connection-oriented service to
the applications that are running on the layer above,
guaranteed delivery of the application-layer messages, flow
control, and congestion control mechanism. UDP provides a
connectionless, best-effort service to the applications that
are running in the layer above without reliability, flow, or
congestion control. In this layer the packet is called a
segment.
Network layer: This layer is responsible for moving the
© 2025 Assignment Expert
packet of information, called a datagram, from one host to
another. The network layer is responsible for delivering the
Exampromax - Stuvia US
datagram to the Transport layer on the destination host. In
this layer there are the IP Protocol and the routing tables.
Data Link layer: Packets are referred to as frames. Examples
include: ethernet, ppp, wifi. Responsible for moving the
frames from one node (host or router) to the next node.
Services offered by the data link layer protocol include
reliable delivery (transmission of the data from one
transmitting node, across one link, to the receiving node.
Physical layer: This layer is the actual hardware responsible
to transfer bits within a frame between two nodes c
Provide examples of popular protocols at each layer of the five-layered
Internet model.
Correct Answer
Application: NFS, DNS, SNMP, ftp, rcp, telnet, HTTP
Transport: TCP, UDP
Internet: IP, ARP, ICMP
, Exampromax - Stuvia US 2025/2026
4
Data Link: PPP, IEEE 802.2, Ethernet
Physical Network: Token Ring, RS-232
What is encapsulation, and how is it used in a layered model?
Correct Answer
Encapsulation is when data (called a header) is appended
to the packet through each layer to signify its on the
correct path to the destination host.
© 2025 Assignment Expert
What is the end-to-end (e2e) principle?
Exampromax - Stuvia US
Correct Answer
A design choice that shaped the current internet
architecture. It states the network core should be simple
and minimal, while the end systems should carry the
intelligence. Network functions should be simple and
essential commonly used functions so any host can utilize
the service and higher form functions should be built into
the application itself. Lower level layers should be
independent and free to perform only their designed
function and the higher-level layers deal with the more
intricate functions that deal with the specific application.
What are the examples of a violation of e2e principle?
Correct Answer
Violations include firewalls and traffic filters. Firewalls
violate because they are intermediate devices that are
operated between two end hosts and they can drop the end
1
CS6250 Computer Networks Exam 1 Questions
and Answers and Graded
What are advantages and disadvantages of a layered architecture?
Correct Answer
Each protocol layer offers different services. Some
advantages are scalability, flexibility, and ease of adding /
removing components making it easier for cost-effective
implementations. Disadvantages include: some layers
functionality depends on the information from the other
© 2025 Assignment Expert
layer and violates the goal of layer separation; one layer
Exampromax - Stuvia US
may duplicate lower layer functionalities; overhead both in
computation and in message headers caused by abstraction
barriers between layers.
What are the differences and similarities of the OSI model and five-layered
Internet model?
Correct Answer
The OSI model and the 5-layered Internet Model have
many of the same layers, with the difference being three of
the layers are combined in the 5-layered model. Specifically
the five-layer model combines the application,
presentation, and session layers from the OSI model into a
single application layer.
What are sockets?
Correct Answer
, Exampromax - Stuvia US 2025/2026
2
A network socket is a software structure within a network
node of a computer network that serves as an endpoint for
sending and receiving data across the network. The
structure and properties of a socket are defined by an
application programming interface (API) for the networking
architecture. Sockets are created only during the lifetime of
a process of an application running in the
node.https://en.wikipedia.org/wiki/Network_socket."A
process sends messages into, and receives messages from,
the network through a software interface called a socket.
Let's consider an analogy to help us understand processes
and sockets. A process is analogous to a house and its
© 2025 Assignment Expert
socket is analogous to its door....a socket is the interface
Exampromax - Stuvia US
between the application layer and the transport layer within
a host." - Kurose and Ross, 2.1
Describe each layer of the OSI model.
Correct Answer
Application layer: Service, Interface, Protocol. Ex: Turn on
your smartphone and look at the list of apps. (HTTP, SMTP,
FTP, DNS)
Presentation layer: Plays intermediate role of formatting the
information received from the layer below and delivering it
to the application layer. Ex: converting big endian to little
endian.
Session layer: Responsible for the mechanism that manages
the different transport streams that belong to the same
session between end-user and application process. Ex:
teleconference app, it is responsible for tying together
audio and video streaming.
, Exampromax - Stuvia US 2025/2026
3
Transport layer: Responsible for the end-to-end
communication between end hosts. 2 transport protocols,
TCP and UDP. TCP includes a connection-oriented service to
the applications that are running on the layer above,
guaranteed delivery of the application-layer messages, flow
control, and congestion control mechanism. UDP provides a
connectionless, best-effort service to the applications that
are running in the layer above without reliability, flow, or
congestion control. In this layer the packet is called a
segment.
Network layer: This layer is responsible for moving the
© 2025 Assignment Expert
packet of information, called a datagram, from one host to
another. The network layer is responsible for delivering the
Exampromax - Stuvia US
datagram to the Transport layer on the destination host. In
this layer there are the IP Protocol and the routing tables.
Data Link layer: Packets are referred to as frames. Examples
include: ethernet, ppp, wifi. Responsible for moving the
frames from one node (host or router) to the next node.
Services offered by the data link layer protocol include
reliable delivery (transmission of the data from one
transmitting node, across one link, to the receiving node.
Physical layer: This layer is the actual hardware responsible
to transfer bits within a frame between two nodes c
Provide examples of popular protocols at each layer of the five-layered
Internet model.
Correct Answer
Application: NFS, DNS, SNMP, ftp, rcp, telnet, HTTP
Transport: TCP, UDP
Internet: IP, ARP, ICMP
, Exampromax - Stuvia US 2025/2026
4
Data Link: PPP, IEEE 802.2, Ethernet
Physical Network: Token Ring, RS-232
What is encapsulation, and how is it used in a layered model?
Correct Answer
Encapsulation is when data (called a header) is appended
to the packet through each layer to signify its on the
correct path to the destination host.
© 2025 Assignment Expert
What is the end-to-end (e2e) principle?
Exampromax - Stuvia US
Correct Answer
A design choice that shaped the current internet
architecture. It states the network core should be simple
and minimal, while the end systems should carry the
intelligence. Network functions should be simple and
essential commonly used functions so any host can utilize
the service and higher form functions should be built into
the application itself. Lower level layers should be
independent and free to perform only their designed
function and the higher-level layers deal with the more
intricate functions that deal with the specific application.
What are the examples of a violation of e2e principle?
Correct Answer
Violations include firewalls and traffic filters. Firewalls
violate because they are intermediate devices that are
operated between two end hosts and they can drop the end
