CS 6250 Computer Networks Exam 1
UPDATED ACTUAL QUESTIONS AND
CORRECT ANSWERS
What are advantages and disadvantages of a layered architecture? - CORRECT ANSWER Each
protocol layer offers different services.
Layered Architecture - CORRECT ANSWER Each protocol layer offers different services.
Layered Architecture Advantages - CORRECT ANSWER - Scalability,
- Flexibility
- Ease of adding / removing components making it easier for cost-effective implementations.
Layered Architecture Disadvantages - CORRECT ANSWER - 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 - CORRECT ANSWER Many of the layers
are the same
OSI and Five-Layered Internet model Differences - CORRECT ANSWER - 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? - CORRECT 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.
- ."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. - CORRECT ANSWER - 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 - CORRECT ANSWER - Service, Interface, Protocol.
Ex: Turn on your smartphone and look at the list of apps. (HTTP, SMTP, FTP, DNS)
,OSI Model Presentation Layer - CORRECT ANSWER - 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 - CORRECT ANSWER - 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 - CORRECT ANSWER - 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 - CORRECT ANSWER - 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 - CORRECT ANSWER - 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 - CORRECT ANSWER 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
Data Link: PPP, IEEE 802.2, Ethernet
Physical Network: Token Ring, RS-232
5-Layer Model - Transport Layer Protocols - CORRECT ANSWER - TCP- UDP
5-Layer Model - Application Layer Protocols - CORRECT ANSWER - NFS
- DNS
- SNMP
UPDATED ACTUAL QUESTIONS AND
CORRECT ANSWERS
What are advantages and disadvantages of a layered architecture? - CORRECT ANSWER Each
protocol layer offers different services.
Layered Architecture - CORRECT ANSWER Each protocol layer offers different services.
Layered Architecture Advantages - CORRECT ANSWER - Scalability,
- Flexibility
- Ease of adding / removing components making it easier for cost-effective implementations.
Layered Architecture Disadvantages - CORRECT ANSWER - 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 - CORRECT ANSWER Many of the layers
are the same
OSI and Five-Layered Internet model Differences - CORRECT ANSWER - 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? - CORRECT 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.
- ."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. - CORRECT ANSWER - 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 - CORRECT ANSWER - Service, Interface, Protocol.
Ex: Turn on your smartphone and look at the list of apps. (HTTP, SMTP, FTP, DNS)
,OSI Model Presentation Layer - CORRECT ANSWER - 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 - CORRECT ANSWER - 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 - CORRECT ANSWER - 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 - CORRECT ANSWER - 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 - CORRECT ANSWER - 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 - CORRECT ANSWER 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
Data Link: PPP, IEEE 802.2, Ethernet
Physical Network: Token Ring, RS-232
5-Layer Model - Transport Layer Protocols - CORRECT ANSWER - TCP- UDP
5-Layer Model - Application Layer Protocols - CORRECT ANSWER - NFS
- DNS
- SNMP
