Computer network performance indicators

Computer network performance indicators computer network performance generally refers to its several important performance indicators. However, in addition to these important performance indicators, some non-performance features also have a great impact on the performance of computer networks. Performance indicators measure the performance of computer networks in different ways. The following describes the seven common performance indicators. Www.2cto.com 1. The computer sends signals at a rate in digital format. Bit is the unit of data volume in the computer and the unit of information used in information theory. BITs are derived from binary digit (a binary number). Therefore, a bit is one or zero of binary numbers. The speed in network technology refers to the rate at which a host connected to a computer network transmits data over a digital channel, also known as data rate or bit rate ). The unit of speed is B/s (bit per second) or bit/s. It can also be written as bps, that is, bit per second. When the data rate is high, kb/s (k = 10 ^ 3 = thousands) and Mb/s (M = 10 ^ 6 = Mb) can be used), Gb/s (G = 10 ^ 9 = Kyrgyzstan) or Tb/s (T = 10 ^ 12 = too ). At present, it is generally used to describe the network speed, such as 100 M Ethernet, rather than B/s, which means the ethernet with a data rate of Mb/s. The data rate here usually refers to the rated rate. Www.2cto.com 2. bandwidth has two meanings: (1) bandwidth originally refers to the band width of a signal. The bandwidth of a Signal refers to the frequency range occupied by various frequency components of the signal. For example, the standard bandwidth of telephone signals transmitted on traditional communication lines is 3.1 kHz (from 3.1Hz to kHz, that is, the frequency range of the main component of the sound ). In this sense, the bandwidth unit is Hz. The main line of the previous communication transmits analog signals (that is, continuously changing signals ). Therefore, the signal band range that a communication line can pass is the bandwidth of the line. (2) In a computer network, loans are used to indicate the ability of the network's communication lines to transmit data, therefore, network bandwidth indicates the "maximum data volume" that can be passed from one point of the network to another in a unit time. In this sense, the bandwidth unit is "bits per second", that is, B/s. Sub-units are usually preceded by multiples of thousands (k), megabytes (M), gih (G), and Tai (T. 3. throughput indicates the amount of data transmitted over a network (or channel or interface) per unit time. The throughput market entry is used to measure networks in the real world so that you can know how much data actually passes through the network. Obviously, throughput is limited by the bandwidth of the network or the rated rate of the network. For example, if the rated rate of a 100 Mb/s Ethernet is 100 Mb/s, this value is also the absolute upper limit of the Ethernet throughput. Therefore, for 100 Mb/s Ethernet, the typical throughput may be only 70 Mb/s. Www.2cto.com 4. time required to transmit latency index data (one packet or group) from one end of the network (or link) to the other end. Latency is a very important performance indicator, also known as latency or delay. The latency in the network is composed of the following parts: (1) the transmission latency is the time required by the host or vro to send data frames, that is, from the first bit of the data frame to be sent, the time required to send the last bit of the frame. Transmission latency is also known as transmission latency. Transmission latency = data frame length (B)/transmission rate (B/s ). For a certain network, the transmission latency is not fixed, but proportional to the length of the sent frame and inversely proportional to the sending rate. (2) The propagation delay is the time required to transmit electromagnetic waves in a channel. Propagation latency = channel length (m)/propagation rate of electromagnetic waves on the channel (m/s) the propagation rate of electromagnetic waves in free space is the speed of light, that is, 3.0 × 10 ^ 5 km/s. The propagation rate of electromagnetic waves in network transmission media is lower than that in free space. The propagation rate in copper cable is about 2.3 × 10 ^ 5 km/s, the propagation rate in the optical fiber is about 2.0 × 10 ^ 5 km/s. (3) Processing latency when a host or router receives a group, it takes a certain amount of time to process it, analyze the group header, extract data from the group, perform error checks, and find appropriate routes, this results in processing latency. Www.2cto.com (4) the queuing delay group goes through many routers during network transmission. However, after entering the vro, the Group must queue in the input queue for processing. After the router determines the forwarding interface, it also needs to queue in the output queue for forwarding. This results in queue latency. The queue latency usually depends on the network traffic at the time. In this way, the total latency of data in the network is the total latency = Sending latency + propagation latency + Processing latency + queuing latency for high-speed network links, the increase is only the data transmission rate, rather than the bit transmission rate on the link. The propagation rate of the electromagnetic wave of load information on the communication line is irrelevant to the data transmission rate. The improved data transmission rate only reduces the data transmission latency. 5. The latency bandwidth product multiply the propagation latency and bandwidth of the two preceding network performance measurements, and then wait for another measurement: The propagation latency bandwidth product, that is, latency bandwidth product = propagation latency × bandwidth www.2cto.com. For example, the propagation latency is 20 ms, and the bandwidth is 10 Mb/s, latency bandwidth product = 20x10x10 ^ 3/1000 = 2x10 ^ 5 bit. This indicates that if the sender sends data continuously, the sender has sent 0.2 million bits when the first bit is about to reach the destination, the 0.2 million bits are all moving forward on the link. 6. The round-trip time RTT is in the computer network, and the round-trip time RTT is also an important performance indicator, indicating the total time from the sender's sending of data to the sender's receipt of confirmation from the receiver. For the example above, the round-trip time RTT is 40 ms, and the product of the round-trip time and bandwidth is 4 × 10 ^ 5 (bit ). Apparently, the round-trip time is related to the length of the sent group. The round-trip time for sending a long data block should be more than the round-trip time for sending a short data block. The meaning of the round-trip bandwidth product is that when the sender continuously sends data, it can receive confirmation from the other party in time, but many BITs have been sent to the link. For the above example, assume that the receiver of the Data finds an error in time and notifies the sender to stop sending immediately, but the sender has also sent 0.4 million bits. Www.2cto.com 7. utilization rate credit channel utilization rate and network utilization rate. The channel utilization rate indicates that a channel is used for a certain percentage of time. The network utilization rate is the weighted average value of the channel utilization rate of the entire network. The higher the channel utilization, the better. This is because, according to the queuing theory, when the utilization rate of a channel increases, the latency caused by the channel increases rapidly. If D0 represents the latency when the network is idle, and D represents the current network latency, you can use a simple formula (D = D0/(1-U) to represent the relationship between D, D0 and utilization U. The U value is between 0 and 1. When the network utilization is close to the maximum value of 1, the network latency approaches infinity.