Network link dimensioning : a measurement & modeling based approach


Meent, Remco van de (2006) Network link dimensioning : a measurement & modeling based approach. thesis.

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Abstract:Adequate network link dimensioning requires a thorough insight into the interrelationship between: (i) the traffic offered (in terms of the average load, but also its fluctuations), (ii) the desired level of performance, and (iii) the required bandwidth capacity. It is clear that more capacity is needed when the average traffic load becomes higher, the fluctuations become fiercer, or the performance criterion becomesmore stringent. Existing approaches to network link dimensioning are often based on rules of thumb, e.g., `take the average traffic rate at timeswhen the network is relatively busy, and add 30%to cater for fluctuations¿. Clearly, such an approach does not explicitly incorporate the fierceness of the traffic rate¿s fluctuations, or the desired level of performance.
A common approach to estimate the average traffic rate is as follows. A networkmanager regularly polls the so-called Interfaces Group MIB via the Simple NetworkManagement Protocol (SNMP), for instance through a tool such as the Multi-Router Traffic Grapher (MRTG). This yields the average rate of the offered traffic since the last poll. The polling interval generally is in the order of 5minutes. Evidently, the fierceness of fluctuation of the traffic rate within these 5 minute intervals is unknown to the network manager. These fluctuations may, however, be considerably large, and noticeable to users of the network. If, at timescales of say 5 seconds, more traffic is offered to a network link than it can transfer during that interval, traffic may be lost. Such loss is generally known as possibly leading to performance degradation and this may well be noticeable to a network user; for instance, entirewords may be lost in a (voice) conversation. Hence, it is in the interest of network users, and for obvious business reasons also to network operators, to have sufficient bandwidth capacity available to meet the demand at timescales considerably smaller than 5 minutes.
In this thesis, we develop an alternative approach to network link dimensioning, which explicitly incorporates the offered traffic in terms of both the average rate as well as its fluctuations at small timescales, and the desired level of performance. This is expressed throughmathematical formulas that give the required bandwidth capacity, given the characteristics of the offered traffic, and the performance criterion.
Item Type:Thesis
Copyright:©2006 CTIT
Electrical Engineering, Mathematics and Computer Science (EEMCS)
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