Multiplex communications – Data flow congestion prevention or control – Control of data admission to the network
Reexamination Certificate
1999-08-19
2003-06-17
Kizou, Hassan (Department: 2662)
Multiplex communications
Data flow congestion prevention or control
Control of data admission to the network
C370S236000
Reexamination Certificate
active
06580691
ABSTRACT:
INTRODUCTION
The present invention relates generally to data networks and more particularly to the design and management of such networks.
For the purposes of this specification the term data network is taken to include any network in which signals originate from a multiplicity of sources. These signals may be in a variety of formats other than the digital packet arrangements associated with local area networks, Internet and intranet applications and may also include telephone networks, cable TV, cellular and satellite communications.
Controlling congestion on high-speed networks is becoming increasingly difficult and expensive. In the case of the Internet, it would historically have been impossible to predict the impact that the provision of services, such as the World Wide Web (WWW) would have generated. The traffic explosion which is now apparent and the extraordinary demand for new services means that bandwidth optimisation is now imperative for any network operator. Asynchronous Transfer Mode (ATM) in which signals are broken up into small cells of uniform size to carry voice, data and video across a network through ATM switches is widely used and is particularly suited to the present invention. The ATM switches at each network node operate at great speed to read the address of an incoming cell and direct it to an appropriate destination. The ongoing challenge to the operators of such networks is the effective management of system resources particularly in light of the increasing number of “bandwidth-hungry” applications.
All networks including ATM networks are of their nature bandwidth limited to some level therefore when the network is asked to communicate a new signal or a set of signals it is essential to accurately determine whether the request can be reliably processed without overloading the capacity of the network.
In connection oriented networks, this determination is sometimes referred to as connection admission control (CAC), and relies on knowledge about the behaviour of both the current signals on the network and of the new signal or signals. When a request is received for a new traffic stream to enter a network, the network will attempt to route that stream through a sequence of switches similar to the ATM switches already mentioned. There may be several different possible routes through the network and the network may have a means of choosing from among them. However, for transmission failure intolerant or time dependent networks a new stream can be handled along a particular route if and only if the sum of resource requirements, that is the current and new, at each switching point along the route does not exceed that switching point available resources. Thus, the present invention may be applied independently at each switching point in the network to determine whether resources will be exceeded at that point if the new stream is accepted.
The subsequent description will refer to connection admission at a particular point in the network.
The first known way of determining whether a new traffic stream can be handled by a network carrying existing traffic streams is to determine the peak resource requirement of each traffic stream. Then, the current capacity of the network used by the existing streams is represented by the sum of their peak requirements, and a new traffic stream can be handled by the network if its peak requirement plus the sum of the peak requirements of the existing streams does not exceed the maximum capacity of the network. This approach to connection admission control is referred to as “allocation on peak”.
In networks where the peak requirement is its usual requirement, this is a simple and efficient method. For example, in a digital telephone network, the peak requirement of a call corresponds its usual requirement so that connection admission control is relatively straight forward. However, in situations where the requirements of a traffic stream vary during the time that stream is being carried by the network, then the method of allocation on peak is potentially wasteful. If, in practice, only a small number of the existing traffic streams are at their peak requirements, there will be a difference between the sum of the peak requirements and the actual capacity of the network used by the traffic streams at any particular time. If allocation on peak was then used as the connection admission control, the control system may prevent a particular signal being handled by the network, when, in fact, the network had sufficient capacity to handle that signal.
Therefore, techniques have been developed which take into account statistical variation of each of the traffic stream, to determine network demands associated with existing traffic streams. The bandwidth requirement per source can be greatly reduced by mixing traffic from many sources. The likelihood of peak demand from all traffic sources occurring simultaneously is small therefore using statistical multiplexing it is possible increase the number of signals which may be carried by the network.
Statistical multiplexing is made possible by the use of buffers in which cells can be stacked in queues, waiting to be processed by the switch. These buffers allow “source modelling”, to be implemented. This source modelling requires a statistical model to be derived from each carried traffic stream to obtain the statistical properties of the traffic streams as a whole. Each statistical model is a mathematical model containing a number of adjustable parameters. The model is then fitted to a respective stream by observing the traffic over a period of time as it passes through the buffers, deducing its statistical properties, and adjusting the parameters of the model to reproduce these. There is an obvious risk that buffers will occasionally overflow, leading to cell-loss, or that long queues will build up, causing unacceptably long transmission delays and the goal is to achieve the gain from statistical multiplexing while avoiding the consequences of congestion.
Where the behaviour of a traffic stream is easily captured by such a model, and where the number of different traffic streams is limited, this source modelling approach may prove satisfactory.
However, in situations where it is difficult to model the behaviour of a traffic stream, or when the number of different types of traffic streams is high, the derivation of appropriate models is computationally demanding. Thus, parametric modelling is unsatisfactory because of the wide variety of traffic types offered to the network, the difficulties in modelling burstiness and the time required to fit parameters. For example, multimedia sources require highly complex models to capture their statistical properties. In situations where the number of source or traffic stream types is large and where sources may adjust their behaviour in response to user input, or network conditions, source modelling does not work satisfactorily.
There is therefore a need for a network which will overcome the aforementioned problems.
SUMMARY OF THE INVENTION
Accordingly there is provided a data network of the type having at least one network switch, the network switch incorporating means for receiving data from more than one network source and means for onward transmission of said data characterised in that the network switch further incorporates means for processing and analysing data from each network source and abstracting a data characteristic from the analysed data.
Preferably the switch incorporates means for receiving a new data processing request from the network source.
Preferably the means for receiving the new data processing request incorporates means for processing, analysing and deriving a data model from the data processing request.
Ideally the switch includes a decision manager, the decision manager comprising:
means for determining a maximum allowable switch throughput parameter;
an integration device for combining the data model and the data characteristic to produce a switch throughput indicator; and
a comparator for comparing the switch throughput in
Bjoerkman Nils
Crosby Simon Andrew
Latour-Henner Alexander
Leslie Ian Malcolm
Lewis John Trevor
Hoang Thai
Jacobson & Holman PLLC
Kizou Hassan
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