Multiplex communications – Data flow congestion prevention or control – Control of data admission to the network
Reexamination Certificate
1998-12-30
2002-11-05
Hsu, Alpus H. (Department: 2662)
Multiplex communications
Data flow congestion prevention or control
Control of data admission to the network
C370S232000, C370S235000, C370S401000, C370S471000, C709S230000, C709S235000
Reexamination Certificate
active
06477143
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to computer networks generally and more particularly to congestion control and avoidance in computer networks.
BACKGROUND OF THE INVENTION
Various techniques are known for congestion control and avoidance in computer networks. Generally speaking congestion control is often effected as a last resort by “load shedding”, which means that data packets are being discarded. Inasmuch as load shedding is extremely wasteful of network bandwidth resources as well as having a significantly negative impact on network performance, efforts have been made to avoid and control congestion without resorting to load shedding.
It is known to attempt to avoid congestion by allowing each node to begin data transmission with a single data segment, awaiting a timely acknowledgment and upon receipt thereof, allowing the node to transmit an increased number of data segments before awaiting a further acknowledgment, the data segments all being of the same size. For each successive received timely acknowledgment, the number of data segments transmitted subsequent thereto remains constant or is increased. The increase factor may be adaptive in response to sensed network congestion, in order to limit the load on the network. In certain cases, the increase factor may become negative or the transmission may be stopped for given intervals.
Various techniques are known whereby a network node controls the transmission rate of a sending node. Among others, routers send “choke” or “source quench” packets to sending nodes in order to slow down their transmission rate.
However, the technique most widely used to restrain the transmission rate of a transmitting node is to drop its packets on route and have the sending node wait in vain for acknowledgment of their receipt. After expiry of a timeout for the acknowledgment, the transmission rate gradually returns to its previous level, preferably in a manner described hereinabove.
The following U.S. patents, the disclosures of which are hereby incorporated by reference, are believed to represent the state of the art in network congestion avoidance and control:
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Hsu Alpus H.
Qureshi Afsar M
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