Local Management: Overview, Setup, and Navigation126More About Rate LimitingRate Limiting enables Service Providers in Multi-Dwelling-Unit (MDU) andsimilar environments wishing to offer varied bandwidth to customers using lowcost 10 Mbps Ethernet or other type of physical connection. Another solution, forthe enterprise, is to provide high priority bandwidth on the network forguaranteed service level agreements.In Multi-Dwelling Unit (MDU) or similar environments, the Rate Limiting featurecan be activated per port to adjust the usable bandwidth on a 10 Mbps Ethernet orother type of physical connection. In residential housing, the service providermay offer multiple Internet service packages, each offering different bandwidth ata different price. These offerings can be supported using low cost 10 MbpsEthernet ports wired to each dwelling.In the enterprise network, this feature (combined with Layer 3/4 prioritization)can provide guaranteed delivery of high priority traffic through a congestednetwork fabric. This is accomplished through the construction of a committedinformation rate (CIR) fabric within the traditional best effort enterprise LANfabric.ExampleThis is a simple example intended to show how the Rate Limiting feature can beapplied to solve a problem.Assume that a network built using SmartSwitch 9000 chassis in the wiring closetsare interconnected with SmartSwitch Routers using gigabit Ethernet links. Alsoassume that 100 users are attached to each SmartSwitch 9000 chassis through100 Mbps Ethernet ports. If each user attempted to transfer data out of the wiringcloset at the maximum possible rate, there could be up to 10 Gbps (100 users x100 Mbps) of traffic attempting to leave the chassis over a single gigabit link. Inthis situation, much of the traffic will be arbitrarily dropped.Now assume that the system administrator wants to guarantee the delivery ofService Access Point SAP R/3 traffic by prioritizing it above all other incomingtraffic to the chassis. Unless the inbound rate of the SAP traffic can be controlled,the guarantee still cannot be made because of the potential for oversubscription ofthe outbound gigabit link by high priority traffic.When allocating the maximum rate per port, the maximum bandwidth of theuplink must be kept in mind. For example, if the ports are all set to 10 Mbps andthere are 24 ports, this equals 240 Mbps of bandwidth. If the uplink is only100 Mbps, there is an obvious problem if the network administrator guaranteedmore bandwidth than the uplink can support.NOTE
