Latest version update 2026 CS6250 Computer
Networks Exam 1 practice exam questions and
answers (verified answers) with complete solutions.
What are the differences and similarities of the OSI model and five-
layered Internet model? - 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 advantages and disadvantages of a layered architecture? -
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 layer and violates the goal of layer separation;
one layer may duplicate lower layer functionalities; overhead both in
computation and in message headers caused by abstraction barriers
between layers.
What are sockets? - ANSWER: 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 socket is analogous to its door....a socket is the interface
between the application layer and the transport layer within a host." -
Kurose and Ross, 2.1
,Provide examples of popular protocols at each layer of the five-layered
Internet model. - ANSWER: Application: NFS, DNS, SNMP, ftp, rcp,
telnet, HTTP
Transport: TCP, UDP
Internet: IP, ARP, ICMP
Data Link: PPP, IEEE 802.2, Ethernet
Physical Network: Token Ring, RS-232
Describe each layer of the OSI model. - 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.
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 packet of
information, called a datagram, from one host to another. The network
layer is responsible for delivering the 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
What is encapsulation, and how is it used in a layered model? -
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.
What is the end-to-end (e2e) principle? - 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? - 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 host communications. Network Address
Translation (NAT) boxes are also a violation because it uses the single
public IP address and distributes a new IP scheme to the hosts
connected to it to route data through re-writing the header info to route to
the correct destination host. NAT boxes are a violation because they are
not globally addressable or routable.
What is the EvoArch model? - ANSWER: An hourglass shaped model of
the Internet where the outer bands are more frequently modified or
replaced and the further in you go the harder it is for that layer to be
altered or modified.
Networks Exam 1 practice exam questions and
answers (verified answers) with complete solutions.
What are the differences and similarities of the OSI model and five-
layered Internet model? - 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 advantages and disadvantages of a layered architecture? -
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 layer and violates the goal of layer separation;
one layer may duplicate lower layer functionalities; overhead both in
computation and in message headers caused by abstraction barriers
between layers.
What are sockets? - ANSWER: 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 socket is analogous to its door....a socket is the interface
between the application layer and the transport layer within a host." -
Kurose and Ross, 2.1
,Provide examples of popular protocols at each layer of the five-layered
Internet model. - ANSWER: Application: NFS, DNS, SNMP, ftp, rcp,
telnet, HTTP
Transport: TCP, UDP
Internet: IP, ARP, ICMP
Data Link: PPP, IEEE 802.2, Ethernet
Physical Network: Token Ring, RS-232
Describe each layer of the OSI model. - 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.
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 packet of
information, called a datagram, from one host to another. The network
layer is responsible for delivering the 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
What is encapsulation, and how is it used in a layered model? -
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.
What is the end-to-end (e2e) principle? - 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? - 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 host communications. Network Address
Translation (NAT) boxes are also a violation because it uses the single
public IP address and distributes a new IP scheme to the hosts
connected to it to route data through re-writing the header info to route to
the correct destination host. NAT boxes are a violation because they are
not globally addressable or routable.
What is the EvoArch model? - ANSWER: An hourglass shaped model of
the Internet where the outer bands are more frequently modified or
replaced and the further in you go the harder it is for that layer to be
altered or modified.
