宽带通信系统与网络测量技术 课件 (4)

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1. 吞吐率 -测试方法
以指定速率给被测设备发送一定数量的帧，记录被该设备 转发的帧的数目。如果测试设备发送的帧数等于被测设备 接收到的帧数，测试设备接收到的帧数小于发送的帧数， 则降低发送速率，重新测试。当测试设备发送的和被测设 备转发的测试帧数相同时，最大的转发速率即为吞吐率。
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❖ The latency is timestamp B minus timestamp A。RFC 1242
❖ The test MUST be repeated at least 20 times with the reported value being the average of the recorded values.
Devices) 。
❖ RFC2889：IETF制定的局域网交换设备的基准测试方法 （Benchmarking Methodology for LAN Switching Devices）。
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6个性能参数
吞吐率（Throughput） 时延（Latency） 丢帧率（Frame loss rate） 背靠背（Back-to-back）性能
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2 时延
❖ For store and forward devices（存储转发设备）:
▪ The time interval starting when the last bit of the input frame reaches the input port and ending when the first bit of the output frame is seen on the output port.
❖ An identifying tag SHOULD be included in one frame after 60 seconds with the type of tag being implementation dependent. The time at which this frame is fully transmitted is recorded (timestamp A). The receiver logic in the test equipment MUST recognize the tag information in the frame stream and record the time at which the tagged frame was received (timestamp B).
▪ 从输入帧的最后一个比特达到输入端口的时刻到输出 帧的第一个比特出现在输出端口上的时刻的时间间隔。
❖ For bit forwarding devices（直通设备）:
▪ The time interval starting when the end of the first bit of the input frame reaches the input port and ending when the start of the first bit of the output frame is seen on the output port.
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第九章 网络设备的指标及其测试
9.1 相关标准
❖ 计算机网络由主机、互连设备和网络协议组成，网络互连设备的 测试是网络测试的重要内容之一。
❖ 网络互连设备，如路由器、交换机等是构成互联网的核心，负责 对网络数据包的转发。网络互连设备的性能影响互联网的性能。
❖ RFC2544 :IETF制定的网络互连设备的基准测试方法 (Benchmarking Methodology for Network Interconnect
系统恢复时间（System recovery） 复位（Reset）
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1. 吞吐率
❖ 定义： 吞吐率是指被测试设备(DUT)在不丢弃测试帧的前提下所 能支持的最大速率。
❖ Definition: ▪ The maximum rate at which none of the offered frames are dropped by the device.
▪ 从输入帧的第一比特达到输入端口的时刻到输出帧的 第一比特出ency test----Procedure:
❖ Send a stream of frames at a particular frame size through the DUT at the determined throughput rate to a specific destination. The stream SHOULD be at least 120 seconds in duration.
❖ The throughput is the fastest rate at which the count of test frames transmitted by the DUT is equal to the number of test frames sent to it by the test equipment.
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1. Throughput test---Procedure
❖ Send a specific number of frames at a specific rate through the DUT and then count the frames that are transmitted by the DUT.
❖ If the count of offered frames is equal to the count of received frames, the fewer frames are received than were transmitted, the rate of the offered stream is reduced and the test is rerun.