CS6250 COMPUTER NETWORK EXAM 1
QUESTIONS WITH VERIFIED ANSWERS
2026 | Exam Prep Bundle | A+ Verified
• What are advantages and disadvantages of a layered architecture? -✓✓Each protocol
layer offers different services.
• Layered Architecture -✓✓Each protocol layer offers different services.
• Layered Architecture Advantages -✓✓- Scalability,
- Flexibility
- Ease of adding / removing components making it easier for cost-effective
implementations.
• Layered Architecture Disadvantages -✓✓- 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
- Overhead in message headers caused by abstraction barriers between layers.
• OSI and Five-Layered Internet model Similarities -✓✓Many of the layers are the same
• OSI and Five-Layered Internet model Differences -✓✓- Three of the layers are
combined in the 5-layered model.
- Specifically the five-layer model combines the
- Application
- Presentation
- Session layers
from the OSI model into a single Application layer.
• What are sockets? -✓✓- 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.
- ."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. -✓✓- Application layer: Service, Interface,
Protocol.
- Presentation layer: Plays intermediate role of formatting the information received from
the layer below and delivering it to the application layer.
- Session layer: Responsible for the mechanism that manages the different transport
streams that belong to the same session between end-user and application process.
- Transport layer: Responsible for the end-to-end communication between end hosts.
Network layer: This layer is responsible for moving the packet of information, called a
datagram, from one host to another.
- Data Link layer: Responsible for moving the frames from one node (host or router) to
the next node.
- Physical layer: This layer is the actual hardware responsible to transfer bits within a
frame between two nodes c
• OSI Model Application Layer -✓✓- Service, Interface, Protocol.
Ex: Turn on your smartphone and look at the list of apps. (HTTP, SMTP, FTP, DNS)
• OSI Model 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.
• OSI Model 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.
• OSI Model Network Layer -✓✓- This layer is responsible for moving the packet of
information, called a datagram, from one host to another.
- 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.
,• OSI Model Transport Layer -✓✓- Responsible for the end-to-end communication
between end hosts.
- 2 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.
• OSI Model 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 ___________ layer protocol include reliable delivery
(transmission of the data from one transmitting node, across one link, to the receiving
node.
• OSI Model 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.
-✓✓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
• 5-Layer Model - Transport Layer Protocols -✓✓- TCP- UDP
• 5-Layer Model - Application Layer Protocols -✓✓- NFS
- DNS
- SNMP
, - FTP
- RCP
- Telnet
- HTTP
• 5-Layer Model - Internet Layer Protocols -✓✓- IP
- ARP
- ICMP
• 5-Layer Model - Data Link Layer Protocols -✓✓- PPP
- IEEE 802.2
- Ethernet
• 5-Layer Model - Physical Network Layer Protocols -✓✓- Token Ring
- RS-232
• What is encapsulation, and how is it used in a layered model? -✓✓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? -✓✓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? -✓✓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.
QUESTIONS WITH VERIFIED ANSWERS
2026 | Exam Prep Bundle | A+ Verified
• What are advantages and disadvantages of a layered architecture? -✓✓Each protocol
layer offers different services.
• Layered Architecture -✓✓Each protocol layer offers different services.
• Layered Architecture Advantages -✓✓- Scalability,
- Flexibility
- Ease of adding / removing components making it easier for cost-effective
implementations.
• Layered Architecture Disadvantages -✓✓- 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
- Overhead in message headers caused by abstraction barriers between layers.
• OSI and Five-Layered Internet model Similarities -✓✓Many of the layers are the same
• OSI and Five-Layered Internet model Differences -✓✓- Three of the layers are
combined in the 5-layered model.
- Specifically the five-layer model combines the
- Application
- Presentation
- Session layers
from the OSI model into a single Application layer.
• What are sockets? -✓✓- 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.
- ."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. -✓✓- Application layer: Service, Interface,
Protocol.
- Presentation layer: Plays intermediate role of formatting the information received from
the layer below and delivering it to the application layer.
- Session layer: Responsible for the mechanism that manages the different transport
streams that belong to the same session between end-user and application process.
- Transport layer: Responsible for the end-to-end communication between end hosts.
Network layer: This layer is responsible for moving the packet of information, called a
datagram, from one host to another.
- Data Link layer: Responsible for moving the frames from one node (host or router) to
the next node.
- Physical layer: This layer is the actual hardware responsible to transfer bits within a
frame between two nodes c
• OSI Model Application Layer -✓✓- Service, Interface, Protocol.
Ex: Turn on your smartphone and look at the list of apps. (HTTP, SMTP, FTP, DNS)
• OSI Model 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.
• OSI Model 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.
• OSI Model Network Layer -✓✓- This layer is responsible for moving the packet of
information, called a datagram, from one host to another.
- 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.
,• OSI Model Transport Layer -✓✓- Responsible for the end-to-end communication
between end hosts.
- 2 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.
• OSI Model 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 ___________ layer protocol include reliable delivery
(transmission of the data from one transmitting node, across one link, to the receiving
node.
• OSI Model 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.
-✓✓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
• 5-Layer Model - Transport Layer Protocols -✓✓- TCP- UDP
• 5-Layer Model - Application Layer Protocols -✓✓- NFS
- DNS
- SNMP
, - FTP
- RCP
- Telnet
- HTTP
• 5-Layer Model - Internet Layer Protocols -✓✓- IP
- ARP
- ICMP
• 5-Layer Model - Data Link Layer Protocols -✓✓- PPP
- IEEE 802.2
- Ethernet
• 5-Layer Model - Physical Network Layer Protocols -✓✓- Token Ring
- RS-232
• What is encapsulation, and how is it used in a layered model? -✓✓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? -✓✓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? -✓✓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.
