Which layer is responsible for process to process delivery of packets in IOT?

The OSI model divides the tasks involved with moving information between networked computers into seven smaller, more manageable task groups. Each of the seven OSI layers is assigned a task or group of tasks.

The transport layer's tasks include error correction as well as segmenting and desegmenting data before and after it's transported across the network. This layer is also responsible for flow control and making sure that segmented data is delivered over the network in the correct sequence.

Layer 4 (the transport layer) uses the transmission control protocol (TCP) & user data protocol (UDP) to carry out its tasks.

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Techopedia Explains Transport Layer

The transport layer provides communication between application processes running on different hosts within a layered architecture of protocols and other network components.

In a nutshell, the transport layer collects message segments from applications, and transmits them into the network (Layer 3). Here the segments are reassembled into fully-fledged messages, and passed on to Layer 7.

This layer enables the host to send and receive error corrected data, packets or messages over a network and is the network component that allows multiplexing.

Transport layers (Layer 4) work transparently within the layers above to deliver and receive data without errors.

The send side breaks application messages into segments (packets) and passes them on to the network layer (Layer 3).

The receiving side then reassembles segments into messages and passes them to the application layer (Layer 7).

What Services Can the Transport Layer Provide?

Connection-Oriented Communication

Devices at the end-points of a network communication establish a handshake protocol such as TCP to ensure a connection is robust before data is exchanged.

The weakness of this method is that for each delivered message, there is a requirement for an acknowledgment, adding considerable network load compared to self-error-correcting packets.

The repeated requests cause significant slowdown of network speed when defective byte streams or datagrams are sent.

Same Order Delivery

Ensures that packets are always delivered in strict sequence by assigning them a number.

Although the network layer is responsible, the transport layer can fix any discrepancies in sequence caused by packet drops or device interruption by reordering them.

Data Integrity

Using checksums, the data integrity across all the delivery layers can be ensured.

These checksums guarantee that the data transmitted is the same as the data received and that is not corrupt.

Missing or corrupted data can be resent by requesting retransmission from other layers.

Flow Control

Devices at each end of a network connection often have no way of knowing each other's capabilities in terms of data throughput.

Data can end up being sent faster than the speed at which the receiving device is able to buffer or process it. When this happens, buffer overruns can cause complete communication breakdowns.

Conversely, if the receiving device is not receiving data fast enough, this causes a buffer underrun, which may well cause an unnecessary reduction in network performance.

Flow control ensures that the data is sent at a rate that is acceptable for both sides by managing data flow.

Traffic Control

Digital communications networks are subject to bandwidth and processing speed restrictions, which can mean a huge amount of potential for data congestion on the network.

This network congestion can affect almost every part of a network. The transport layer can identify the symptoms of overloaded nodes and reduced flow rates and take the proper steps to remediate these issues.

Multiplexing

The transmission of multiple packet streams from unrelated applications or other sources (multiplexing) across a network requires some very dedicated control mechanisms, which are found in the transport layer.

This multiplexing allows the use of simultaneous applications over a network such as when different internet browsers are opened on the same computer.

In the OSI model, multiplexing is handled in the service layer.

Byte orientation

Some applications prefer to receive byte streams instead of packets; the transport layer allows for the transmission of byte-oriented data streams if required.

The OSI Model is a logical and conceptual model that defines network communication used by systems open to interconnection and communication with other systems. The Open System Interconnection (OSI Model) also defines a logical network and effectively describes computer packet transfer by using various layers of protocols.

In this tutorial, you will learn:

• Characteristics of OSI Model
• Why of OSI Model?
• What is OSI Model?
• History of OSI Model
• 7 Layers of the OSI Model
• Physical Layer
• Data Link Layer
• Transport Layer
• Network Layer
• Session Layer
• Presentation Layer
• Application Layer
• Interaction Between OSI Model Layers
• Protocols supported at various levels
• Differences between OSI & TCP/IP
• Advantages of the OSI Model
• Disadvantages of the OSI Model

Characteristics of OSI Model

Here are some important characteristics of the OSI model:

• A layer should only be created where the definite levels of abstraction are needed.
• The function of each layer should be selected as per the internationally standardized protocols.
• The number of layers should be large so that separate functions should not be put in the same layer. At the same time, it should be small enough so that architecture doesn’t become very complicated.
• In the OSI model, each layer relies on the next lower layer to perform primitive functions. Every level should able to provide services to the next higher layer
• Changes made in one layer should not need changes in other lavers.

Why of OSI Model?

• Helps you to understand communication over a network
• Troubleshooting is easier by separating functions into different network layers.
• Helps you to understand new technologies as they are developed.
• Allows you to compare primary functional relationships on various network layers.

History of OSI Model

Here are essential landmarks from the history of OSI model:

• In the late 1970s, the ISO conducted a program to develop general standards and methods of networking.
• In 1973, an Experimental Packet Switched System in the UK identified the requirement for defining the higher-level protocols.
• In the year 1983, OSI model was initially intended to be a detailed specification of actual interfaces.
• In 1984, the OSI architecture was formally adopted by ISO as an international standard

7 Layers of the OSI Model

OSI model is a layered server architecture system in which each layer is defined according to a specific function to perform. All these seven layers work collaboratively to transmit the data from one layer to another.

• The Upper Layers: It deals with application issues and mostly implemented only in software. The highest is closest to the end system user. In this layer, communication from one end-user to another begins by using the interaction between the application layer. It will process all the way to end-user.
• The Lower Layers: These layers handle activities related to data transport. The physical layer and datalink layers also implemented in software and hardware.

Upper and Lower layers further divide network architecture into seven different layers as below

• Application
• Presentation
• Session
• Transport
• Network, Data-link
• Physical layers

Let’s Study each layer in detail:

Physical Layer

The physical layer helps you to define the electrical and physical specifications of the data connection. This level establishes the relationship between a device and a physical transmission medium. The physical layer is not concerned with protocols or other such higher-layer items.

Examples of hardware in the physical layer are network adapters, ethernet, repeaters, networking hubs, etc.

Data Link Layer:

Data link layer corrects errors which can occur at the physical layer. The layer allows you to define the protocol to establish and terminates a connection between two connected network devices.

It is IP address understandable layer, which helps you to define logical addressing so that any endpoint should be identified.

The layer also helps you implement routing of packets through a network. It helps you to define the best path, which allows you to take data from the source to the destination.

The data link layer is subdivided into two types of sublayers:

1. Media Access Control (MAC) layer- It is responsible for controlling how device in a network gain access to medium and permits to transmit data.
2. Logical link control layer- This layer is responsible for identity and encapsulating network-layer protocols and allows you to find the error.

Important Functions of Datalink Layer:

• Framing which divides the data from Network layer into frames.
• Allows you to add header to the frame to define the physical address of the source and the destination machine
• Adds Logical addresses of the sender and receivers
• It is also responsible for the sourcing process to the destination process delivery of the entire message.
• It also offers a system for error control in which it detects retransmits damage or lost frames.
• Datalink layer also provides a mechanism to transmit data over independent networks which are linked together.

Transport Layer:

The transport layer builds on the network layer to provide data transport from a process on a source machine to a process on a destination machine. It is hosted using single or multiple networks, and also maintains the quality of service functions.

It determines how much data should be sent where and at what rate. This layer builds on the message which are received from the application layer. It helps ensure that data units are delivered error-free and in sequence.

Transport layer helps you to control the reliability of a link through flow control, error control, and segmentation or desegmentation.

The transport layer also offers an acknowledgment of the successful data transmission and sends the next data in case no errors occurred. TCP is the best-known example of the transport layer.

Important functions of Transport Layers:

• It divides the message received from the session layer into segments and numbers them to make a sequence.
• Transport layer makes sure that the message is delivered to the correct process on the destination machine.
• It also makes sure that the entire message arrives without any error else it should be retransmitted.

Network Layer:

The network layer provides the functional and procedural means of transferring variable length data sequences from one node to another connected in “different networks”.

Message delivery at the network layer does not give any guaranteed to be reliable network layer protocol.

Layer-management protocols that belong to the network layer are:

1. routing protocols
2. multicast group management
3. network-layer address assignment.

Session Layer

Session Layer controls the dialogues between computers. It helps you to establish starting and terminating the connections between the local and remote application.

This layer request for a logical connection which should be established on end user’s requirement. This layer handles all the important log-on or password validation.

Session layer offers services like dialog discipline, which can be duplex or half-duplex. It is mostly implemented in application environments that use remote procedure calls.

Important function of Session Layer:

• It establishes, maintains, and ends a session.
• Session layer enables two systems to enter into a dialog
• It also allows a process to add a checkpoint to steam of data.

Presentation Layer

Presentation layer allows you to define the form in which the data is to exchange between the two communicating entities. It also helps you to handles data compression and data encryption.

This layer transforms data into the form which is accepted by the application. It also formats and encrypts data which should be sent across all the networks. This layer is also known as a syntax layer.

The function of Presentation Layers:

• Character code translation from ASCII to EBCDIC.
• Data compression: Allows to reduce the number of bits that needs to be transmitted on the network.
• Data encryption: Helps you to encrypt data for security purposes — for example, password encryption.
• It provides a user interface and support for services like email and file transfer.

Application Layer

Application layer interacts with an application program, which is the highest level of OSI model. The application layer is the OSI layer, which is closest to the end-user. It means OSI application layer allows users to interact with other software application.

Application layer interacts with software applications to implement a communicating component. The interpretation of data by the application program is always outside the scope of the OSI model.

Example of the application layer is an application such as file transfer, email, remote login, etc.

The function of the Application Layers are:

• Application-layer helps you to identify communication partners, determining resource availability, and synchronizing communication.
• It allows users to log on to a remote host
• This layer provides various e-mail services
• This application offers distributed database sources and access for global information about various objects and services.

Interaction Between OSI Model Layers

Information sent from a one computer application to another needs to pass through each of the OSI layers.

Which layer is responsible for process to process delivery of packets?

Which layer is responsible for port to port delivery of packets?

Which layer is responsible for ensuring packet delivery from host to destination?