The transport layer of the transmission control protocol/Internet protocol (TCP/IP) protocol stack is an end-to-end layer that aims to provide, as much as possible, the required quality-of-service (QoS) to the application layer, at the lowest cost. To assure this functionality, the transport layer aims to achieve a trade-off between the QoS parameters requested by the application layer and the QoS available at the network layer (which is a function of the instantaneous traffic).
The QoS parameters dealt with and negotiated by the transport layer includes the following:
• Requested bit rate in each direction
• Bit error rate
• Maximum end-to-end delay
• Maximum end-to-end jitter
• Priority rules
• Probability ...