CS6250 COMPUTER NETWORK EXAM 1
(Latest 2026 Update) | Complete Guide with
Questions and Verified Answers | 100%
Correct | Graded A+
‣ 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 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
,‣ 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
, ‣ 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
‣ 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
(Latest 2026 Update) | Complete Guide with
Questions and Verified Answers | 100%
Correct | Graded A+
‣ 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 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
,‣ 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
, ‣ 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
‣ 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
