User controlled adaptive flow control for packet networks

DETAILED DESCRIPTION In accordance with the illustrative embodiment of the present invention, the state of congestion in a packet communications system is made available to the user applications utilizing that communications system.
That is, the network facilities monitor the network so as to obtain the best possible information concerning the values of all of the network transmission parameters, including throughput, latency, jitter and so forth.
However, since the network does not have the best information concerning how best to adapt to changes in these transmission parameters, these transmission parameter values are made available to each user application.
More particularly, a programming interface with user applications is provided with extensions which enable the network software to inform the user applications of the values of these transmission parameters.
The user application can be provided with a system call to inquire about the network transmission parameters, or the network software can asynchronously supply the user application with signals indicating the occurrence of events affecting transmission parameters.
These event signals can be handled like other external event signals such as timer events, semaphore events, user signals, and so forth, which are already part of most operating systems.
The latter technique, advising user applications of transmission parameter affecting events, is the preferred alternative since the user application may not know the best times to query the network for transmission parameters.
In accordance with one feature of the present invention, a certain amount of hysteresis in introduced into the event reporting process to prevent the application from responding to transient changes which do not persist over the long term.
In particular, each application notifies the network of the Quality of Service (QoS) specifications required for that application.
Such QoS specifications consist of a lower bound, an upper bound and an operating level for that parameter