How Qos Needs A Performance Guarantee Essay

1102 Words Nov 6th, 2016 5 Pages
QoS needs a performance guarantee, so admission control needs to be more stringent. When a host offers a flow with the corresponding QoS requirement, it is admitted if and only if its QoS constraints can be satisfied without jeopardizing the QoS constraints of existing calls in the network. If the flow is accepted, the network needs to reserve capacity in advance at each router on the path to ensure QoS requirement is met. If any router on the path does not have the reservation for this flow, congestion may happen, and congestion at any router on the path can cause the performance to fail to meet the QoS SLA.
One solution is to find the single best path between each source and each destination, then only send traffic along the best path. However, because each best path is fixed, when there are traffic flows are already in the path, other flows attempt to share the same path will get rejected. An alternative for QoS guarantees for new flow is to choose a different path for the flow that has excess capacity. This is called QoS routing. It is similar to the example given in the last section. To relieve this situation, routers can also choose multiple outgoing paths to gain more capacity in the network links, and split the traffic over multiple output links equally or in proportion to the capacity of each outgoing link.
There are a few things to be noted for the QoS admission control. The first one is to recognize that the criteria/specification for accepting or…

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