Multiplex communications – Data flow congestion prevention or control – Flow control of data transmission through a network
Reexamination Certificate
2000-06-29
2004-07-20
Ton, Dang (Department: 2661)
Multiplex communications
Data flow congestion prevention or control
Flow control of data transmission through a network
C370S230000, C370S395200, C370S468000
Reexamination Certificate
active
06765873
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application claims priority from European application 99480063.9, filed Jul. 13, 1999 (MM/DD/YY), which is hereby incorporated by reference. The contents of the present application are not necessarily identical to the contents of the priority document.
BACKGROUND OF THE INVENTION
1. Technical Field
The invention relates to high-speed packet switched networks. More particularly, the invention relates to a connection bandwidth management process and system which rely on an efficient monitoring of the network resources occupancy to re-compute the bandwidth allocated to connections boarded on a given link so that the overall bandwidth capacity of the link is not exceeded.
2. Description of the Related Art
The emergence of high speed networking technologies such as ATM cell-based or Frame Relay based technologies, now makes possible the integration of multiple types of traffic having different quality of service requirements (QoS), like speech, video and data, over the same communication network, which is often referred to as a “broadband” network. The communication circuits which may be shared in such network include transmission lines, program controlled processors, nodes or links, and data or packets buffers. Traffic QoS requirements are taken into account during the path selection process, and can be defined as a set of measurable quantities or parameters that describe the user's perception of the service offered by the network. Such parameters include the connection setup delay, the connection blocking probability, the loss probability, the error probability, the end-to-end transit delay and the end-to-end delay variation also referred to as jitter. Real-time traffics have more constraining requirements than non-real-time ones i.e. end-to-end delays and jitters. It is necessary to be able to give priority to the real-time packets in order to minimize these delays. Meanwhile, the packet loss must be guaranteed both for real-time and non-real-time applications which have reserved bandwidth in the network, while it is not mandatory for non-reserved type of traffic.
In this context, network users want the ability to request and be granted service level agreements (SLAs). An SLA is an agreement by the network provider to supply a guaranteed level of connectivity for a given price. The agreement is reciprocal in that the user also commits not to go beyond a certain level of network usage. The level of connectivity can be expressed in many ways, including the following: the Bandwidth (number of bits per second), the Latency (end-to-end delay), the Availability (degree of uninterrupted service), the Loss Probability, and the Security (guarantee that only the intended parties can participate in a communication).
Another important objective of the networks providers is to optimize the network resources utilization. Indeed, communication networks have at their disposal limited resources to ensure an efficient packets transmission, and while transmission costs per byte continue to drop year after year, transmission costs are likely to continue to represent the major expense of operating future telecommunication networks as the demand for bandwidth increases. More specifically, considering wide area networks (also referred to as “backbone networks”), the cost of physical connectivity between sites is frequently estimated at 80% of the overall cost. The connectivity can come in the form of a leased line, X.25 service, frame relay bearer service (FRBS), ATM bearer service (ATMBS), X.25, or a virtual private network. As higher-speed links become available, the cost per bit may decrease, but the absolute cost of links will remain significant. Therefore, there is a need to minimize the net cost per transmitted bit for all connectivity options and link speeds. Minimizing the cost per bit means squeezing the maximum possible utilization out of every link.
Thus, considerable efforts have been spent on designing flow and congestion control processes, bandwidth reservation mechanisms, routing algorithms to manage the network bandwidth and do network capacity planning i.e. optimize the configuration of the established connections (bandwidth allocated, path selected, etc.).
In order to comply with both optimizing network resources utilization and guaranteeing satisfactory SLAs to the network customers, high speed networks generally include monitoring software systems to monitor the status of their nodes and links. These monitoring systems typically rely on counters implemented at switching node level. From a network resources monitoring point of view, the most important counters are those which reflect the behavior of the “bottleneck” resources of the network because they will also reflect the end to end behavior or quality of the service delivered. In high speed networks, the switching nodes are generally oversized in terms of performances compared to the communication links. As a matter of fact, switching nodes are “one time cost” for a network owner while lines cost is recurrent for example in a month period basis in case of leased lines, and is also much higher as previously stated. In order to minimize the overall cost of a network, communication lines are sized in order to handle the traffic requirements but no more, and accordingly their throughput is always less than that of a switching node. Therefore, in a high speed network, communication links generally constitute the “bottleneck resources”.
Links utilization data are typically expressed in terms of percentage of bandwidth utilized per unit of time. Links utilization is typically evaluated as follows:
Considering a link 1 whose maximum speed (i.e. bandwidth) is S cells/bytes per second (where S denotes an integer), and assuming that the counters values associated with that link are polled every T time units (where T denotes an integer, e.g., T=15 minutes). Then, the computed utilization estimation U(l) of link l associated with each measurement time interval T would be expressed by the following formula:
U
(
1
)
T
=
N
S
×
T
where N denotes the number of cells/packets received during measurement period T, and where T is expressed in seconds. U(l)
T
is expressed in percentage of link utilization.
These link utilization values, which are computed every time interval T (e.g., T=15 minutes) and periodically retrieved, may be processed in a statistics server associated with the network to compute an average link utilization which is the average of link utilization values U(l)
T
, computed during a day, or over several days or weeks.
Currently, high speed packet switching networks can support hundreds of thousands of connections. Moreover, tens to hundreds of connections may be configured for each newly subscribed user to the network. Very seldom does a customer know the amount of bandwidth required for each of his connections. In addition, network customers usually take some margin in the bandwidth requested for their connections to anticipate an increase of their traffic needs. The foregoing results in that an important difference is observed between the bandwidth reserved (i.e., contracted) by the customers' connections and the actual bandwidth used.
One assumption widely considered by large networks providers is that, due to the important number of customers boarded, the diversity of the locations, and the different types of service requested, there is a very low probability that a high number of connections will be active at the same time.
Therefore, in this context, in order to maximize the network resources utilization, network providers typically practice what is commonly known as “overbooking” or “oversubscription” of their network links. That is, taking advantage of the statistical multiplexing of connections over the links, they allow more connections to be established on a link than the link may theoretically accept with regard to its total bandwidth capacity.
However, the link oversubscription technique suffers from the shortcomings that if a certain nu
Fichou Aline
Galand Claude
Le Pennec Jean-Francois
Dillon & Yudell LLP
McConnell Daniel E.
Phan Tri H.
Ton Dang
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