Test network and inter-network throughput -- OneTouch Network Test Application

In Internet search engines, the most commonly used keyword for network testing is "network speed testing". From the log of an Heng website, statistics on the access volume of this keyword can account for 30% of the keywords of network testing technology. This shows how much people are concerned about the speed test of the network. This article discusses the methods and applications for testing network and inter-network throughput. The methods and cases in this article are the summary of the testing practices of anheng Network Testing Service Center, in this case, the Fluke network's OneTouch network testing instrument was used.

The "network speed test" can be explained from many aspects. From the perspective of Internet users, the main concern is the speed at which network resources are accessed through the Internet. To this end, many websites also provide test scripts and services to test the access speed from the visitor to the site. This test method is very simple, but due to many factors, the test results are generally only used as a performance evaluation for specific applications that access this specific website, such as http and ftp, this type of content is not discussed here.

When maintaining an enterprise network, we often need to test the transmission capability of links between networks or networks. The testing methods are usually diverse based on the testing purpose. For example, the throughput test during network installation and maintenance requires testing the IP performance that spans the trunk, WAN, or VPN; pressure tests are required to locate faults in LAN segments or assist in analysis of other network applications. The methods and requirements for these tests are different. Responsible for network installation, network engineers, network administrators, and engineers who provide high-speed optical link ethernet to the user's telecommunications department will use throughput and pressurization tests at work to check link performance.

Throughput Test

Such tests can solve the following problems:

Throughput of the Peer Wan/LAN on the test end
Test the performance of IP addresses that span WAN connections and compare the capabilities of currently used WAN links with the promised information rate (CIR) against SLA.
Perform benchmark and congestion tests when installing VPN
Test the ing between the mode, frame size, or network rate of the network device. It is used to evaluate the optimization and setting of devices such as the modem, FRADS, Hub, switch, or router.
Throughput testing requires end-to-end testing by the dual-end of the tested link, for enterprise network management and maintenance engineers, they do not need to understand or test physical networks during end-to-end testing. Because IP addresses are network interconnection platforms that carry application services, such physical networks in the end-to-end link test can be wireless networks, routing environments, transparent networks, or even non-symmetric networks such as xDSL and Cable Modem ).

The simplest and most commonly used and valid throughput test method is to test access over the Ethernet network at both ends of the link. During the test, the sender calculates the speed of the received frame on the receiver at the specified sending speed. Throughput is the number/time of frames received by the receiver. The test results are obtained at different rates by changing the frame length and repeating the above tests. Note: You can perform tests repeatedly to determine the throughput at different transmission speeds)

One thing that needs to be emphasized is that when maintaining a running network, the throughput test must be conducted online, that is, the existing network services and network connections cannot be interrupted, other network traffic exists during the test. In this case, the test results are of great significance for evaluating the network capabilities of existing businesses and planning to increase the number of network sites and expand the evaluation of network applications.

Test method: There are many test methods and methods for end-to-end testing. There are two main types: one is PC-based testing, the other is the use of specialized testing instruments. Generally, a large traffic volume, for example, greater than 30 Mbps, is tested using a testing instrument, this is because the testing instrument is not affected by the operating system, Nic, device driver and configuration as the PC-based testing software. The tester can provide stable, independent, and reproducible testing results.

Application Case 1: throughput test for enterprise networks, figure 2.

In this test application, A, B, C, and D are access points that can be selected for testing. They can form different links with the tester connected to the hub, through the throughput test of these links, the corresponding network bottlenecks and network segments that identify performance problems can be found.

Figure 2. network throughput Test Access Point

Display of test results

1. The test parameters are displayed in the following sections: test speed, test time, frame length, and test mode of the upper and lower rows. These parameters are pre-tested by the parameter owner. Before the test, the tester can adjust and set the test parameters as needed.
2. The above and downstream modes respectively show the actual transmission rate, of successful transmission, and the number of frames lost in the test. This is the test result of the tester according to the settings described in ①.
3. The test link parameters are displayed: local and remote IP addresses and routers.
4. Number of router hops
5. display the current Ethernet Access Mode

Application Case 2: Test xDSL link throughput, figure 4.

Figure 4. Test Access Point of xDSL Link

We have such a test requirement for xDSL testing applications: 1. determine the maximum transmission rate of xDSL on a specific link; 2. determine the maximum transmission distance at a specific rate.

To meet the test requirements of requirement 1, you must have a test function that can be automatically incrementing and determined, that is to say, before the test, set the start rate and the maximum rate of the test, and then define an auto increment step, after the test starts, when the effective transmission rate under the tested rate exceeds 95%, the test continues at a higher speed until the effective transmission rate is lower than 95%, and the maximum transmission rate of the link can be determined.

The above method has been used to evaluate the cross-brand ADSL modem in foreign countries. The method is simple and practical, and the evaluation result is intuitive.

Network pressurization test

Such tests can be used to solve the following problems:

Apply a predetermined size of network traffic on a CIDR block to test the error status of the CIDR block or activate potential errors.
Test the network error discovery, statistics, and report functions by generating and sending bad frames.
Verify the port statistics of RMON and SNMP probes on network devices such as routers and switches.
Simulate additional users and applications on the LAN
One-way fast Ping tests connectivity along suspicious links to identify link bottlenecks
Standalone test of the two-way throughput of the Network
Test the symmetric throughput of a WAN link
Test method: In the network pressurization test, you can use MAC or IP-based methods. For MAC-based tests, data transmission is performed on Ethernet network segments, the pressure test based on the IP packet is to test the traffic sending of the specified IP address. It can test the remote site across the router.

You can select ultra-long/short frames for sending when selecting the data to be sent. Such Ethernet error frames cannot or may not span the vro ), most of them are used to determine the reflection of the network management system and alarm system when frame errors occur on the physical network, as well as the accuracy of the statistical information.

Another very effective pressurization test is the fast IP Ping test. Generally, the ICMP Ping command is a test method that needs to wait for a response after sending an ICMP request. This method can only verify network connectivity, however, you cannot verify the network response in high-traffic scenarios. Although Ping is the most frequently used method in all network testing methods, it is usually not used for network pressurization to reflect testing because it can hardly generate traffic pressure on the network. Fast IP Ping is an effective method to make up for this regret. The test instrument does not wait for the response of the current request before sending the next ICMP request, instead, an ICMP request is sent to the tested target with a constant traffic according to the tester's settings. This method sounds like a hacker attack? In fact, we have used this method multiple times to test the ability to reflect the pressurized site. Therefore, we recommend that you exercise caution when using this test !)

Test Case 3: one-way pressurization test, as shown in Figure 5.

Figure 5 shows that this test is a tunable continuous test.

The current test speed is displayed. Note that the speed is × 2.
Change in the utilization caused by the pressurized traffic sent to the network
Number of Ping responses that can be received in the current send

From the case, we can clearly see that for the pressure of sending 512 bytes per frame at a rate of 10 frames/Second, the converted network traffic is 41.6Kbps × 2. At this time, the network utilization rate is 78 frames/second, And the Ping response reaches 10 Ping/s, that is, no packet loss occurs in the test.

In this case, we can adjust the number of frames sent per second or the length of the sent frames to test the Ping response. This one-way fast IP Ping test brings great capabilities to testers. Although it is a single-ended tester, ICMP data packets are bidirectional data streams, this test method can be used to conveniently test the impact of encrypted/decrypted communication between routers in the tested link on network traffic performance. It can also be used to test the sensitivity of the link to the packet length, which provides a strong proof for adjusting the network settings.

The above network throughput testing method is one of the most frequently used methods in network maintenance. the engineers of anheng network testing center use these methods reasonably and effectively in their actual work, find many faults, especially performance-related network faults ). There are many other effective and excellent methods in the traffic test, such as using the protocol analyzer to reproduce the data traffic. In the future, we will gradually introduce them to you.