Features and tests of WLAN

No one is skeptical that WLAN is currently the most popular technology and market in the network industry. However, the monitoring and testing of WLAN is still a problem that is often ignored, people are even using laptops and wireless NICs to test and accept wireless projects. This reminds us of the early Ethernet testing scenarios. The following is a discussion of the basic concepts of wireless testing. In fact, from the perspective of development sources, wireless LAN and Ethernet are the same source. In terms of MAC Layer Protocol features, wireless LAN and wired Ethernet share the same transmission channel, currently, most enterprise applications of Wireless LAN are used to supplement wired networks. Therefore, the test of Wireless LAN has many similarities with that of wired Ethernet.

Features of WLAN

Although the MAC layer protocol of the wireless LAN is different from that of the Ethernet, the Ethernet transmission protocol is (CSMA/CD), and the wireless network standard uses CSMA/CA (with multi-path access with a carrier that avoids conflict) the common feature of MAC mode is that multiple access devices share a communication channel. WLAN actually has a "line". For 802.11b wireless LAN, this line is an 83.5MHz band in the GHz band. In fact, WLAN is much more complex than wired LAN in terms of design, management, and maintenance, and there are more variables that affect network performance, sometimes even unpredictable. The CSMA/CA protocol is indeed inferior to the CSMA/CD Protocol. However, due to the characteristics of wireless transmission, CSMA/CD Protocol cannot be used in the wireless LAN. The channel utilization is affected by the transmission distance and the degree of openness. When the distance is far or there are obstacles, there will be hidden terminal problems, reducing the channel utilization. Specifically, the highest channel utilization rate is related to the transmission rate. In IEEE802.11b Wireless LAN, the maximum channel utilization can reach 90% at 1 Mbps, while the maximum channel utilization is only about 65% at 11 Mbps. However, these shortcomings do not cover up the advantages of Wireless LAN. The first is to get rid of the limitations of the line, which is a turning point for network development. Secondly, because the MAC layer protocol uses the CSMA/CA protocol, it can be seamlessly connected to the standard Ethernet protocol. Although a wireless LAN is somewhat different from a wired LAN and requires an access point (AP) connection, its compatibility makes it easy for a WLAN to work in conjunction with the LAN into a single network. Third, WLAN solves network application problems in areas that are not suitable for cabling or cannot be cabled.

WLAN testing includes five aspects

First, test the channel.

Different from wiring tests, signal strength, noise intensity, and signal-to-noise ratio are the most important indicators in channel tests. The wireless transmission mode is microwave transmission, and the signal strength test is to verify the signal attenuation, the intensity of microwave attenuation is related to factors such as distance, obstacle shielding, and AP transmit power. The signal strength plays a decisive role in the connection of sites over the Internet in WLAN. As WLAN 802.11 uses public channels, other communication or industrial devices, such as microwave ovens, mobile phones, and 2.4G/5.8G microwave transmission facilities, may cause noise to the WLAN, it causes great interference to WLAN transmission.

Secondly, WLAN Network Performance Testing

Similar to wired network tests, network performance tests are classified into basic tests and operation monitoring. basic tests include AP throughput testing, Ping, site and AP list analysis, the tester evaluated the basic running conditions of WLAN through these tests. On the basis of basic tests, the operation monitoring module adds comprehensive real-time AP site performance analysis, real-time traffic analysis, SSID grouping analysis, and classification and composition of various packets and signal frames transmitted over 802.11 networks. real-time network utilization and throughput, and the transmission rate of any node, these parameters reflect the current working status of the WLAN.

Third, protocol analysis

For WLAN, because it has many special frame formats in terms of protocol, real-time packet capture decoding is an indispensable method in WLAN testing. Because our protocol analysis is aimed at network maintenance management, we only need to understand the next three layers in the decoding process. The next three layers contain basic information about Maintenance and Management of almost all networks, of course, if there are conditions for full-layer decoding, there is no harm.

Fourth, Fault Diagnosis

This is an essential application in network operation and maintenance, WLAN fault diagnosis is based on comprehensive analysis of the channel test, network performance analysis, packet capture decoding, and other test results. WLAN fault diagnosis is divided into two parts: First, network performance fault diagnosis (network performance evaluation), including connectivity fault, low-speed transmission, and weak AP signal; second, network security Fault Diagnosis (Network Security Evaluation), which is a unique issue of WLAN networks. Due to the characteristics of microwave transmission, in a certain space, microwave signals can be received by all signal receiving devices in this space. Therefore, IEEE constantly introduces security protocols for WLAN, from the initial WEP, LEAP, MIC, TKIP, and 802.1X security protocols to the latest WPA, we can say that the security factor of WLAN is getting higher and higher. However, most of the current security problems are caused by users' initial settings. Most enterprise users do not even open the most basic security mode WEP, just as your door does not have a lock, anyone can access your network at will, and the network is very insecure. Discovering existing security vulnerabilities is the most basic requirement for WLAN security testing. For enterprise networks, simply enabling WEP is far from enough. WEP is a static key. For a well-trained hacker, only two small software is needed to attack WEP networks. Therefore, an authentication problem is raised. How to authenticate whether a device is a normal device in the network or a device that is illegally intruded into the device, no matter what means illegal intruders use to intrude into the device, network security is an insecure factor. It is also a very important requirement for WLAN security testing to discover and quickly locate illegal intrusion devices.

Fifth, maintenance issues in WLAN applications

Comprehensive management documents make network operation and maintenance easier. In addition to the detailed status list of each Wireless Access Point and site, management documents must also include the test report in the document, both basic network security and performance analysis and real-time report order archiving are required. This forms a long-term dynamic network analysis document for the entire network, it provides a convenient way for further network upgrade and maintenance.

With the continuous development of wireless LAN technology, the launch and commercialization of 802.11a and 802.11g standards bring new business opportunities to the development of wireless networks, as China Mobile, China Telecom, and China Netcom have successively invested in the construction of WLAN broadband access hotspots, WLAN has become synonymous with mobile commerce and mobile Internet access, and major universities are competing to build WLAN, to meet the increasing Internet access needs of students and faculty and staff, large enterprises also use WLAN as the development direction for the next network construction, the requirements for multi-frequency testing and distributed testing are also mentioned on the agenda. Distributed testing and supporting 802.11a/B/g multi-frequency testing have become the preferred solution for WLAN testing.