H3C S5120-EI Series Configuration Manual

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H3C S5120-EI Series Configuration Manual Manual pdf 49 page image

5-3Traffic policing is widely used in policing traffic entering the networks of internet service providers(ISPs). It can classify the policed traffic and take pre-defined policing actions on each packetdepending on the evaluation result:z Forwarding the traffic if the evaluation result is “conforming.”z Dropping the traffic if the evaluation result is “excess.”z Marking a conforming packet or a non-conforming packet with a new DSCP precedence value andforwarding the packet.Traffic ShapingTraffic shaping provides measures to adjust the rate of outbound traffic actively. A typical trafficshaping application is to limit the local traffic output rate according to the downstream traffic policingparameters.The difference between traffic policing and GTS is that packets to be dropped in traffic policing arecached in a buffer or queue in GTS, as shown in Figure 5-2. When there are enough tokens in thetoken bucket, these cached packets are sent at an even rate. Traffic shaping may result in anadditional delay while traffic policing does not.Figure 5-2 Schematic diagram for GTSTokenbucketPackets droppedPacketclassificationPackets to be sentthrough this interfacePackets sentTokens are put into thebucket at the set rateQueueFor example, in Figure 5-3, Switch A sends packets to Switch B. Switch B performs traffic policing onpackets from Switch A and drops packets exceeding the limit.Figure 5-3 GTS applicationYou can perform traffic shaping for the packets on the outgoing interface of Switch A to avoidunnecessary packet loss. Packets exceeding the limit are cached in Switch A. Once resources are