CS6250 - Computer Networks Q&A
What are advantages and disadvantages of a layered architecture? - =Separation of concerns among
logical layers promotes flexibility, scalibility, and maintainability. Multiple applications can reuse the
components. It enables teams to work on different parts with minimal dependencies on other teams
What are the similarities of the OSI model and five-layered Internet model? - =They are both based on
layered architecture.
The are comparable to each other - see image 1
Both are networking standards
What are the differences of the OSI model and five-layered Internet model? - =OSI is a generic model
based on the functions of each layer. TCP is a protocol oriented standard.
OSI uses 3 upper layers (application, presentation, and session) while TCP just uses application.
Likewise, OSI uses 2 Lower layers (Physical and DataLink) while TCP just uses Link
What is a socket? - =A socket is one endpoint of a two-way communication link between two programs
running on the network.
A socket is bound to a port number so that the TCP layer can identify the application that data is
destined to be sent to.
Physical Layer - =The lowest, or first, layer of the OSI model. Protocols in this layer generate and detect
signals so as to transmit and receive data over a network medium. These protocols also set the data
transmission rate and monitor data error rates, but do not provide error correction.
The lowest layer of the OSI Model is concerned with electrically or optically transmitting raw
unstructured data bits across the network from the physical layer of the sending device to the physical
layer of the receiving device. It can include specifications such as voltages, pin layout, cabling, and radio
frequencies. At the physical layer, one might find "physical" resources such as network hubs, cabling,
repeaters, network adapters or modems.
,OSI Data Link Layer - =At the data link layer, directly connected nodes are used to perform node-to-node
data transfer where data is packaged into frames. The data link layer also corrects errors that may have
occurred at the physical layer.
The data link layer encompasses two sub-layers of its own. The first, media access control (MAC),
provides flow control and multiplexing for device transmissions over a network. The second, the logical
link control (LLC), provides flow and error control over the physical medium as well as identifies line
protocols.
OSI Network Layer - =The network layer is responsible for receiving frames from the data link layer, and
delivering them to their intended destinations among based on the addresses contained inside the
frame. The network layer finds the destination by using logical addresses, such as IP (internet protocol).
At this layer, routers are a crucial component used to quite literally route information where it needs to
go between networks.
OSI Transport Layer - =The transport layer manages the delivery and error checking of data packets. It
regulates the size, sequencing, and ultimately the transfer of data between systems and hosts. One of
the most common examples of the transport layer is TCP or the Transmission Control Protocol.
OSI Session Layer - =The session layer controls the conversations between different computers. A
session or connection between machines is set up, managed, and termined at layer 5. Session layer
services also include authentication and reconnections.
OSI Presentation Layer - =The presentation layer formats or translates data for the application layer
based on the syntax or semantics that the application accepts. Because of this, it at times also called the
syntax layer. This layer can also handle the encryption and decryption required by the application layer.
OSI Application Layer - =At this layer, both the end user and the application layer interact directly with
the software application. This layer sees network services provided to end-user applications such as a
web browser or Office 365. The application layer identifies communication partners, resource
availability, and synchronizes communication.
5 Layer Internet Model - Application Layer - =As you might have guessed, the Application layer is where
applications requiring network communications live. Examples of these applications include email clients
, and web browsers. These applications use the Transport Layer to send requests to connect to remote
hosts.
5 Layer Internet Model - Transport Layer - =The Transport layer establishes the connection between
applications running on different hosts. It uses TCP for reliable connections and UDP for fast
connections. It keeps track of the processes running in the applications above it by assigning port
numbers to them and uses the Network layer to access the TCP/IP network.
5 Layer Internet Model - Network Layer - =The Network layer is responsible for creating the packets that
move across the network. It uses IP addresses to identify the packet's source and destination.
5 Layer Internet Model - Data Link Layer - =The Data Link layer is responsible for creating the frames that
move across the network. These frames encapsulate the packets and use MAC addresses to identify the
source and destination.
5 Layer Internet Model - Physical Layer - =The Physical layer encodes and decodes the bits found in a
frame and includes the transceiver that drives and receives the signals on the network.
What is encapsulation, and how is it used in a layered model? - =In networking model, the terms
encapsulation and de-encapsulation refer to a process in which protocol information is added to the
data and removed from the data when it passes through the layers.
Protocol information can be added before and after the data. If information is added before the data, it
is known as header. If information is added after the data, it is known as trailer.
What is the end-to-end (e2e) principle? - =When a function has to be supported in a networked system,
the designer often asks if it should be implemented at the end systems; or should it be implemented
within the communication subsystem that interconnects all the end systems. The end-to-end argument
or principle states that it's proper to implement the function in the end systems. The communication
system itself may provide a partial implementation but only as a performance enhancement.
The architecture and growth of the Internet was shaped by the end-to-end principle. It allowed us to
keep the Internet simple and add features quickly to end systems. The principle enabled innovation.
End to End Principle Example - =An example of the end-to-end principle is that of an arbitrarily reliable
file transfer between two endpoints in a distributed network of a varying, nontrivial size:[3] The only
What are advantages and disadvantages of a layered architecture? - =Separation of concerns among
logical layers promotes flexibility, scalibility, and maintainability. Multiple applications can reuse the
components. It enables teams to work on different parts with minimal dependencies on other teams
What are the similarities of the OSI model and five-layered Internet model? - =They are both based on
layered architecture.
The are comparable to each other - see image 1
Both are networking standards
What are the differences of the OSI model and five-layered Internet model? - =OSI is a generic model
based on the functions of each layer. TCP is a protocol oriented standard.
OSI uses 3 upper layers (application, presentation, and session) while TCP just uses application.
Likewise, OSI uses 2 Lower layers (Physical and DataLink) while TCP just uses Link
What is a socket? - =A socket is one endpoint of a two-way communication link between two programs
running on the network.
A socket is bound to a port number so that the TCP layer can identify the application that data is
destined to be sent to.
Physical Layer - =The lowest, or first, layer of the OSI model. Protocols in this layer generate and detect
signals so as to transmit and receive data over a network medium. These protocols also set the data
transmission rate and monitor data error rates, but do not provide error correction.
The lowest layer of the OSI Model is concerned with electrically or optically transmitting raw
unstructured data bits across the network from the physical layer of the sending device to the physical
layer of the receiving device. It can include specifications such as voltages, pin layout, cabling, and radio
frequencies. At the physical layer, one might find "physical" resources such as network hubs, cabling,
repeaters, network adapters or modems.
,OSI Data Link Layer - =At the data link layer, directly connected nodes are used to perform node-to-node
data transfer where data is packaged into frames. The data link layer also corrects errors that may have
occurred at the physical layer.
The data link layer encompasses two sub-layers of its own. The first, media access control (MAC),
provides flow control and multiplexing for device transmissions over a network. The second, the logical
link control (LLC), provides flow and error control over the physical medium as well as identifies line
protocols.
OSI Network Layer - =The network layer is responsible for receiving frames from the data link layer, and
delivering them to their intended destinations among based on the addresses contained inside the
frame. The network layer finds the destination by using logical addresses, such as IP (internet protocol).
At this layer, routers are a crucial component used to quite literally route information where it needs to
go between networks.
OSI Transport Layer - =The transport layer manages the delivery and error checking of data packets. It
regulates the size, sequencing, and ultimately the transfer of data between systems and hosts. One of
the most common examples of the transport layer is TCP or the Transmission Control Protocol.
OSI Session Layer - =The session layer controls the conversations between different computers. A
session or connection between machines is set up, managed, and termined at layer 5. Session layer
services also include authentication and reconnections.
OSI Presentation Layer - =The presentation layer formats or translates data for the application layer
based on the syntax or semantics that the application accepts. Because of this, it at times also called the
syntax layer. This layer can also handle the encryption and decryption required by the application layer.
OSI Application Layer - =At this layer, both the end user and the application layer interact directly with
the software application. This layer sees network services provided to end-user applications such as a
web browser or Office 365. The application layer identifies communication partners, resource
availability, and synchronizes communication.
5 Layer Internet Model - Application Layer - =As you might have guessed, the Application layer is where
applications requiring network communications live. Examples of these applications include email clients
, and web browsers. These applications use the Transport Layer to send requests to connect to remote
hosts.
5 Layer Internet Model - Transport Layer - =The Transport layer establishes the connection between
applications running on different hosts. It uses TCP for reliable connections and UDP for fast
connections. It keeps track of the processes running in the applications above it by assigning port
numbers to them and uses the Network layer to access the TCP/IP network.
5 Layer Internet Model - Network Layer - =The Network layer is responsible for creating the packets that
move across the network. It uses IP addresses to identify the packet's source and destination.
5 Layer Internet Model - Data Link Layer - =The Data Link layer is responsible for creating the frames that
move across the network. These frames encapsulate the packets and use MAC addresses to identify the
source and destination.
5 Layer Internet Model - Physical Layer - =The Physical layer encodes and decodes the bits found in a
frame and includes the transceiver that drives and receives the signals on the network.
What is encapsulation, and how is it used in a layered model? - =In networking model, the terms
encapsulation and de-encapsulation refer to a process in which protocol information is added to the
data and removed from the data when it passes through the layers.
Protocol information can be added before and after the data. If information is added before the data, it
is known as header. If information is added after the data, it is known as trailer.
What is the end-to-end (e2e) principle? - =When a function has to be supported in a networked system,
the designer often asks if it should be implemented at the end systems; or should it be implemented
within the communication subsystem that interconnects all the end systems. The end-to-end argument
or principle states that it's proper to implement the function in the end systems. The communication
system itself may provide a partial implementation but only as a performance enhancement.
The architecture and growth of the Internet was shaped by the end-to-end principle. It allowed us to
keep the Internet simple and add features quickly to end systems. The principle enabled innovation.
End to End Principle Example - =An example of the end-to-end principle is that of an arbitrarily reliable
file transfer between two endpoints in a distributed network of a varying, nontrivial size:[3] The only
