CS6250 Computer Networks Exam 1 Actual Exam Newest
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What are advantages and disadvantages of a layered architecture? - ans -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 the differences and similarities of the OSI model and five-layered
Internet model? - ans -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? - ans -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. - ans -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. - ans -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? - ans -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? - ans -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? - ans -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? - ans -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.
Explain a round in the EvoArch model. - ans -EvoArch is a discrete-time model that
is executed over rounds. At each round, we perform the following steps: A) We
introduce new nodes, and we place them randomly at layers. B) We examine all
layers, from the top to the bottom, and we perform the following tasks: 1) We
connect the new nodes that we may have just introduced to that layer, by
choosing substrates based on the generality probabilities of the layer below
s(l−1), and by choosing products for them based on the generality probability of
the current layer s(l). 2) We update the value of each node at each layer l, given
that we may have new nodes added to the same layer l. 3) We examine all nodes,
in order of decreasing value in that layer, and remove the nodes that should die.
C) Finally, we stop the execution of the model when the network reaches a given
number of nodes.
What are the ramifications of the hourglass shape of the internet? - ans -A. Many
technologies that were not originally designed for the internet have been
Complete Questions And Correct Detailed Answers|
Already Graded A+
What are advantages and disadvantages of a layered architecture? - ans -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 the differences and similarities of the OSI model and five-layered
Internet model? - ans -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? - ans -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. - ans -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. - ans -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? - ans -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? - ans -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? - ans -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? - ans -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.
Explain a round in the EvoArch model. - ans -EvoArch is a discrete-time model that
is executed over rounds. At each round, we perform the following steps: A) We
introduce new nodes, and we place them randomly at layers. B) We examine all
layers, from the top to the bottom, and we perform the following tasks: 1) We
connect the new nodes that we may have just introduced to that layer, by
choosing substrates based on the generality probabilities of the layer below
s(l−1), and by choosing products for them based on the generality probability of
the current layer s(l). 2) We update the value of each node at each layer l, given
that we may have new nodes added to the same layer l. 3) We examine all nodes,
in order of decreasing value in that layer, and remove the nodes that should die.
C) Finally, we stop the execution of the model when the network reaches a given
number of nodes.
What are the ramifications of the hourglass shape of the internet? - ans -A. Many
technologies that were not originally designed for the internet have been
