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Unformatted text preview: 6.8 Storage-Area Networks 425 its local fair rate, node k sends this rate to its upstream nodes. An upstream node will then limit its own ingress traffic rate with node k ’s local fair rate. In this way, node k can reduce the ingress traffic rate of upstream nodes that get more bandwidth than it does. This can free bandwidth for node k . If node k has an uncongested outgoing link, then it will periodically and incrementally increase the transmission rate of its ingress traffic. Conservative mode. This is the single queue case. There are two prespecified thresh- old transmission rates: low threshold , which indicates that the outgoing link has become congested, and high threshold , which indicates that the link is too con- gested. The high threshold is higher than the low threshold but often less than the actual capacity of the link. Node k will consider its outgoing link to be congested if its transmission rate on the outgoing link is higher than the low threshold rate or if the time between consecutive transmissions exceeds a prespecified maximum delay. When the node is congested, it periodically computes its local fair rate , which is its estimate of the rate that upstream nodes should be sending through its outgoing link. It sendsthe rate that upstream nodes should be sending through its outgoing link....
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- Spring '09
- Bit rate, Input device, Peripheral, Computer peripherals, local fair rate