Network bandwidth estimation methods and Problems

Network bandwidth estimation methods and Problems
I. Current bandwidth estimation methods the current available bandwidth estimation method is mostly based on packet delay on the link. For example, data streams are divided into background data streams (normal data) to detect data packets. Because the bandwidth of the forwarding link is different, the packet link latency changes with the link. We can estimate the link Bottleneck Bandwidth (that is, the minimum link bandwidth) by detecting the packet delay ). Ii. Analysis of bandwidth estimation principles for packet Detection

As shown in the above two figures, the following conclusions are drawn: regardless of the bandwidth transmission or intermediate link, the final bandwidth is equal to the minimum bandwidth on the link, that is, the average bandwidth. Ignore other conditions. Ideally, the bandwidth is equal to the receiving bandwidth. Iii. Method classification: divided into single-ended detection and dual-end detection. Single-ended Detection: Send different time-exp IP packets using ICMP protocol, so as to obtain the latency of each vro, only by sending one end for detection. Detection at both ends: The send and rev segments are calculated by combining timing at both ends. The following mainstream detection methods and tools are listed below: 4. five Problems of link latency estimation 1. the accuracy of time is estimated by measuring the link latency of the sent time, depending on the computer clock. There are several problems. A. Some systems have ms-level system clock, while the control package requires us-level clock. B. The latency of System Call functions is about us, and NIC AND OTHER latencies. 2. packet out-of-order and packet loss: packet out-of-order and packet loss will lead to inaccurate estimation. 3. The General Routing Algorithm of the routing algorithm is the FIFO first-out algorithm. Some routes are not such algorithms, such as overload discarding. 4. Sudden background data is assumed that the background data is partially stable. If the background data changes suddenly, the time interval may be disordered. For example, based on the preceding disadvantages, the general solution is to use a long-series data packet queue for relatively stable detection, however, the length of the dropped packet column and bandwidth usage are also problems. 5. Analyze the disadvantages of single-ended and dual-ends separately. Single-ended disadvantages: 1. reverse data streams have a great impact on forward streams. according to research, the link of A-> B is stable within the hour, that is, the end-to-end path remains unchanged, but the path of B-> A is not necessarily equal to A-> B. 3. The ICMP processing time is MS and will fluctuate. 4. modern routes have limited speed for ICMP, and too many ICMP ports are not allowed. Disadvantages: 1. both ends must have software 2. this article summarizes several basic problems in the available bandwidth measurement system. This section describes the basic features of bandwidth estimation. The next few blogs will analyze each protocol.