CS6250 Computer Networks Exam 1 UPDATED ACTUAL QUESTIONS AND
CORRECT ANSWERS
What are advantages and disadvantages of a layered Each protocol layer offers different services.
architecture?
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 Application: NFS, DNS, SNMP, ftp, rcp, telnet, HTTP
the five-layered Internet model.
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
CORRECT ANSWERS
What are advantages and disadvantages of a layered Each protocol layer offers different services.
architecture?
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 Application: NFS, DNS, SNMP, ftp, rcp, telnet, HTTP
the five-layered Internet model.
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
