Which two protocols work at the transport layer and ensures that data gets to the right applications
The transport layer is the second layer in the TCP/IP model. It is directly beneath the application layer and provides services to it. For the applications, it seems as if the two hosts are connected directly, however, they may actually be separated by a plethora of routers and other types of links. Show
Transport layer protocols have nothing to do with the actual network system, but they are implemented in the end systems and provide process-to-process communication. There may be many processes running on one host system, but the transport layer ensures communication between the right processes. Transport layer protocolsTwo major protocols of the transport layer are:
TCPTCP is a connection-oriented protocol that ensures data reliability and no packet losses. It uses a three-way handshake to first establish the connection between hosts before transmitting any data. It is used in critical applications where packet loss cannot be tolerated. UDPUDP is a connectionless protocol that does not ensure that all the data sent by the sender will be received. It is faster than TCP and is used for video and audio transmission because some data loss can be tolerable. Fundamental functions of the transport layer1) Connection between hostsIt is responsible for end-to-end connection and data transfer between two different end systems. It relies on the lower layers to achieve this. 2) Multiplexing and DemultiplexingTo allow process-to-process communication, the transport layer uses socketsCombination of IP address and port number. One port number is assigned to a running process in a host system. These port numbers are used to distinguish the different processes that may be running at the same host. When multiple applications need to send data from one host, this data is collected and encapsulated into transport layer segments with information related to the host and process that they are being sent to. This is called multiplexing – the information in the transport layer headers is used by the receiver for demultiplexing. Demultiplexing refers to delivering the received data to the correct process in a host. 3) Error detectionDuring transmission, it is possible that the data may get corrupted. Data integrity is checked by the transport layer by using different mechanisms such as a checksum. Moreover, in TCP, acknowledgments and negative acknowledgments are sent by the receiver back to the sender to indicate whether or not the correct(or any) data was received. 4) Reliable data transferTCP provides additional reliability services on top of the ones provided by the network layer. It ensures that there are no errors in the data, no losses, no duplicates, and that all the data chunks are received and put together in order. 5) Congestion and flow controlWhen there is a lot of traffic in the network, packets start to get dropped by the routers because their limit is exceeded. This results in retransmission of the lost data which increases the congestion even more. TCP implements congestion control using an algorithm that has the following parts:
Another problem solved by TCP is that of flow control. A receiver may be overwhelmed if a lot of data is received at the same time and its capacity is reached. TCP ensures that the sender does not transmit more data than the receiver’s capacity. Security threats
Services provided by the Transport LayerThe services provided by the transport layer are similar to those of the data link layer. The data link layer provides the services within a single network while the transport layer provides the services across an internetwork made up of many networks. The data link layer controls the physical layer while the transport layer controls all the lower layers. The services provided by the transport layer protocols can be divided into five categories:
End-to-end delivery:The transport layer transmits the entire message to the destination. Therefore, it ensures the end-to-end delivery of an entire message from a source to the destination. Reliable delivery:The transport layer provides reliability services by retransmitting the lost and damaged packets. The reliable delivery has four aspects:
Error Control
Sequence Control
Loss Control Loss Control is a third aspect of reliability. The transport layer ensures that all the fragments of a transmission arrive at the destination, not some of them. On the sending end, all the fragments of transmission are given sequence numbers by a transport layer. These sequence numbers allow the receiver?s transport layer to identify the missing segment. Duplication Control Duplication Control is the fourth aspect of reliability. The transport layer guarantees that no duplicate data arrive at the destination. Sequence numbers are used to identify the lost packets; similarly, it allows the receiver to identify and discard duplicate segments. Flow ControlFlow control is used to prevent the sender from overwhelming the receiver. If the receiver is overloaded with too much data, then the receiver discards the packets and asking for the retransmission of packets. This increases network congestion and thus, reducing the system performance. The transport layer is responsible for flow control. It uses the sliding window protocol that makes the data transmission more efficient as well as it controls the flow of data so that the receiver does not become overwhelmed. Sliding window protocol is byte oriented rather than frame oriented. MultiplexingThe transport layer uses the multiplexing to improve transmission efficiency. Multiplexing can occur in two ways:
Addressing
Which two protocols works at the transport layer?Transport layer protocols, namely, Transmission Control Protocol (TCP) and User Datagram Protocol (UDP), identify applications communicating with each other by means of port numbers.
What are the two transport protocols?In the IP protocol stack, the most widely used two transport protocols are User Datagram Protocol (UDP) and the Transport Control Protocol (TCP).
Which transport layer protocol is used for reliable data transport?Transmission Control Protocol (TCP) The Transmission Control Protocol (TCP) is a widely used connection-oriented transport layer protocol that provides reliable transfer of data between two end points, and includes mechanisms to handle flow-control, segmentation, error recovery, and multiplexing.
What are the two most common transport protocols?Even though many transport layer protocols exist, the two most commonly used protocols are the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP).
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