The transport layer is the layer in the open system interconnection (OSI) model responsible for end-to-end communication over a network. It provides logical communication between application processes running on different hosts within a layered architecture of protocols and other network components.
The transport layer can provide some or all of the following services:
- Connection-Oriented Communication
- connectionless communication
- flow control
Connectionless communication
The connectionless protocol at the transport layer is UDP (User Datagram Protocol). It is an unreliable (but fast) protocol that does not contain error detection or correction, and is not a reliable delivery mechanism.
Connection-oriented communication
Connection-oriented protocol services are often but not always reliable network services, that provide acknowledgment after successful delivery, and automatic repeat request functions in case of missing data or detected bit-errors. ATM, Frame Relay and MPLS are examples of a connection-oriented, unreliable protocol.
Flow control (data)
flow control is the process of managing the rate of data transmission between two nodes to prevent a fast sender from overwhelming a slow receiver. It provides a mechanism for the receiver to control the transmission speed, so that the receiving node is not overwhelmed with data from transmitting node. Flow control should be distinguished from congestion control, which is used for controlling the flow of data when congestion has actually occurred.[1] Flow control mechanisms can be classified by whether or not the receiving node sends feedback to the sending node.
Sliding Window
A method of flow control in which a receiver gives a transmitter permission to transmit data until a window is full. When the window is full, the transmitter must stop transmitting until the receiver advertises a larger window.
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