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Th`ese de Doctorat de l'université Paris VI Pierre et Marie Curie Mlle ...

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consi<strong>de</strong>ring different constraints like traffic statistics gathered online, n<strong>et</strong>work state infor-<br />

mation reported by core routers, and users’ bandwidth utility functions to allocate n<strong>et</strong>work<br />

resources dynamically and efficiently.<br />

Note that, as we consi<strong>de</strong>r update intervals on the or<strong>de</strong>r of tens of seconds, precise<br />

synchronization b<strong>et</strong>ween ingress routers is not crucial. We discuss in more <strong>de</strong>tails the<br />

tra<strong>de</strong>offs in the s<strong>et</strong>ting of the update interval in Chapter 7.<br />

3.3 Control Messaging<br />

The messages exchanged b<strong>et</strong>ween n<strong>et</strong>work routers, illustrated with arrows in Figure 3.1, are<br />

similar to the control messages proposed in [1] to report persistent congestion or resource<br />

availability. Further, a subs<strong>et</strong> of the messages <strong>de</strong>fined in the RNAP protocol [16] can be<br />

used for these purposes.<br />

Available Bandwidth messages are sent by core routers to ingress routers when unused<br />

bandwidth is <strong>de</strong>tected on some links. These messages can be exchanged either periodi-<br />

cally or only when significant changes are perceived in the n<strong>et</strong>work. On the other hand,<br />

Congestion notification messages are sent immediately by core routers to ingress routers<br />

when some local thresholds are violated. In this case, the bandwidth allocation module is<br />

invoked directly by all ingress routers to re-allocate n<strong>et</strong>work resources accordingly resolving<br />

the congestion situation.<br />

36

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