This is the principle mechanism used in frame relay to ensure that resource requirement, once accepted, can be guaranteed. It is also generally used to achieve high network performance. The network decides whether to accept a new connection request based on the relation of the requested traffic descriptor and the network's residual capacity. The traffic descriptor is defined as a set of parameters communicated to the switching nodes at call set-up time or service subscription time, which characterizes the connection's statistical properties. Once a connection has been established in the network, the edge node of the frame relay network must monitor the connection's traffic flow to ensure that the actual usage of network resources does not exceed this specification.
Frame relay defines some restrictions on the user's information rate.
It allows the network to enforce the end user's information rate and discard information when the subscribed access rate is exceeded. It tries to keep the network operating at its desired equilibrium point so that a certain QOS for the network can be met. The basic idea is to avoid data accumulation inside the network. Frame relay takes advantage of the new, lower error rate links, enabling it to eliminate many of the services provided by X.25. The elimination of functions and fields, combined with digital links, enables frame relay to operate at speeds 20 times greater than X.25.