ipo003a - MDE systems support - HF10 TCP aggregate flows...

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MDE systems support - HF10 TCP aggregate flows Bob Roust 1 Introduction As part of the IP over Optics programme HF10 is attempting to produce realistic models which will allow investi- gation of the behaviour of IP networks when realised over current and future optical systems as the physical layer. Much of the activity is aimed at using the OPNET tool -a discrete event simulator - to simulate the activity of major network components such as routers and transmission links. In order to simplify the modelling of core sytems car- rying thousands of traffic flows it is necessary to characterise the aggregate behaviour of at least a majority of flows (i.e. to provide background traffic loading which interacts with events in a manner sufficiently close to reality) My investigation has been into the characteristics of TCP flows. TCP/IP currently makes up the bulk of traffic with- in internets (>90%) and it is assumed that this will continue to be the case. 2 TCP as a feedback control system In order to understand TCP, I have modelled its behaviours as a non-linear feedback system using MATLAB/SIM- ULINK to construct an analogue of the slow start, fast retransmit and congestion avoidance processes. A number of models were constructed in which packets are modelled as a time discrete incrementing number. This is fed through a time delay and fed back to simulate TCP acknowledgements. The number is allowed to increment only when the value is less than the tcp window plus the last fed back value. The window value is added to and subtract- ed from along the same rules as tcp - various schemes were tried to simulate a missed acknowledgement which would cause the fast retransmit and window halving process. FIGURE 1 shows the result of one such simulation. There is 0.5ms delay in the round trip and an error is introduced
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This note was uploaded on 08/08/2011 for the course CS 310 taught by Professor Aartisingh during the Spring '11 term at National Institute of Technology, Calicut.

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ipo003a - MDE systems support - HF10 TCP aggregate flows...

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