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Jean-Yves Le Boudec (EPFL Lausanne) "Rate adaptation, Congestion Control and Fairness: A Tutorial" Nov 2005
/ref> Note that this definition is substantially different from a common meaning of a ''bottleneck''. Also note, that this definition does not forbid a single link to be a bottleneck for multiple flows. A data rate allocation is max-min fair if and only if a data flow between any two nodes has at least one bottleneck link.
In engineering
Engineering is the use of scientific method, scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, vehicles, and buildings. The discipline of engineering encompasses a broad rang ...
, a bottleneck is a phenomenon by which the performance or capacity of an entire system is severely limited by a single component. The component is sometimes called a bottleneck point. The term is metaphorically derived from the neck of a bottle, where the flow speed of the liquid is limited by its neck.
Formally, a bottleneck lies on a system's critical path and provides the lowest throughput. Bottlenecks are usually avoided by system designers, also a great amount of effort is directed at locating and tuning them. Bottleneck may be for example a processor
Processor may refer to:
Computing Hardware
* Processor (computing)
**Central processing unit (CPU), the hardware within a computer that executes a program
*** Microprocessor, a central processing unit contained on a single integrated circuit (I ...
, a communication link
A data link is the means of connecting one location to another for the purpose of transmitting and receiving digital information (data communication). It can also refer to a set of electronics assemblies, consisting of a transmitter and a recei ...
, a data processing software
Software is a set of computer programs and associated documentation and data. This is in contrast to hardware, from which the system is built and which actually performs the work.
At the lowest programming level, executable code consists ...
, etc.
Bottlenecks in software
Incomputer programming
Computer programming is the process of performing a particular computation (or more generally, accomplishing a specific computing result), usually by designing and building an executable computer program. Programming involves tasks such as ana ...
, tracking down bottlenecks (sometimes known as "hot spots" - sections of the code that execute most frequently - i.e. have the highest execution count) is called performance analysis. Reduction is usually achieved with the help of specialized tools, known as performance analyzers or profilers. The objective being to make those particular sections of code perform as fast as possible to improve overall algorithmic efficiency
In computer science, algorithmic efficiency is a property of an algorithm which relates to the amount of computational resources used by the algorithm. An algorithm must be analyzed to determine its resource usage, and the efficiency of an algor ...
.
Bottlenecks in max-min fairness
In acommunication network
A telecommunications network is a group of nodes interconnected by telecommunications links that are used to exchange messages between the nodes. The links may use a variety of technologies based on the methodologies of circuit switching, messag ...
, sometimes a max-min fairness
In communication networks, multiplexing and the division of scarce resources, max-min fairness is said to be achieved by an allocation if and only if the allocation is feasible and an attempt to increase the allocation of any participant necessari ...
of the network is desired, usually opposed to the basic first-come first-served
Queueing theory is the mathematical study of waiting lines, or queues. A queueing model is constructed so that queue lengths and waiting time can be predicted. Queueing theory is generally considered a branch of operations research because the ...
policy. With max-min fairness, data flow between any two nodes is maximized, but only at the cost of ''more or equally expensive'' data flows. To put it another way, in case of network congestion any data flow is only impacted by smaller or equal flows.
In such context, a ''bottleneck link'' for a given data flow is a link that is fully utilized (is ''saturated'') and of all the flows sharing this link, the given data flow achieves maximum data rate network-wide./ref> Note that this definition is substantially different from a common meaning of a ''bottleneck''. Also note, that this definition does not forbid a single link to be a bottleneck for multiple flows. A data rate allocation is max-min fair if and only if a data flow between any two nodes has at least one bottleneck link.
See also
*Fairness measure Fairness measures or metrics are used in network engineering to determine whether users or applications are receiving a fair share of system resources. There are several mathematical and conceptual definitions of fairness.
TCP fairness
Congestion ...
** Max-min fairness
In communication networks, multiplexing and the division of scarce resources, max-min fairness is said to be achieved by an allocation if and only if the allocation is feasible and an attempt to increase the allocation of any participant necessari ...
* Optimization (computer science)
In computer science, program optimization, code optimization, or software optimization, is the process of modifying a software system to make some aspect of it work more efficiently or use fewer resources. In general, a computer program may be o ...
* Performance engineering
Performance engineering encompasses the techniques applied during a systems development life cycle to ensure the non-functional requirements for performance (such as throughput, latency, or memory usage) will be met. It may be alternatively refe ...
* Profiling (computer programming)
In software engineering, profiling ("program profiling", "software profiling") is a form of dynamic program analysis that measures, for example, the space (memory) or time complexity of a program, the usage of particular instructions, or the fr ...
* Route capacity
Route capacity is the maximum number of vehicles, people, or amount of freight than can travel a given route in a given amount of time, usually an hour. It may be limited by the worst bottleneck (engineering), bottleneck in the system, such as a ...
* Theory of constraints
References
{{Reflist Network performance