CWNP CWNA-109 Exam Dumps

The frame type that is used to reserve the wireless medium for the transmission of high data rate frames that may not be understood by all clients connected to the BSS isRTS. RTS stands for Request to Send and is a control frame that is sent by a station to request access to the medium for a specified duration. The RTS frame contains the source and destination MAC addresses, as well as a Network Allocation Vector (NAV) value that indicates how long the medium will be occupied. The destination station responds with a Clear to Send (CTS) frame that echoes the NAV value and grants permission to the source station. All other stations in the BSS hear either the RTS or CTS frame and update their NAV timers accordingly, deferring their transmissions until the medium is free. The RTS/CTS mechanism can be used to prevent hidden node problems, reduce collisions, and protect high data rate frames that use features such as 802.11n or 802.11ac that may not be compatible with legacy stations. ACK, Beacon, and PS-Poll are not used to reserve the medium for high data rate frames.Reference:[CWNP Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 112; [CWNA: Certified Wireless Network Administrator Official Study Guide: Exam CWNA-109], page 102.

The statement that in modern networks, both centralized and distributed data forwarding work well for most standard office deployments is true about WLAN performance. Data forwarding refers to how wireless frames are transmitted from wireless clients to wired networks or vice versa through wireless access points (APs). Centralized data forwarding means that all wireless frames are sent to a central controller or gateway before being forwarded to their destinations. Distributed data forwarding means that wireless frames are forwarded directly by the APs to their destinations without going through a central controller or gateway. Both methods have their advantages and disadvantages, depending on the network size, topology, traffic pattern, security, and management requirements. However, in modern networks, both methods can achieve high performance and scalability for most standard office deployments, as they can leverage advanced features such as fast roaming, load balancing, quality of service, and encryption. The other statements about WLAN performance are false. In most WLANs, special skill or tuning is required to get peak performance, such as selecting the appropriate channel, power, data rate, and antenna settings. WLANs perform worse as more wireless clients connect with each AP, as they cause more contention and interference on the wireless medium.To get the best performance out of an AP, you should not disable data rates of 72 Mbps and lower, as they are needed for backward compatibility and range extension.Reference:CWNA-109 Study Guide, Chapter 9: Wireless LAN Architecture, page 2811

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The clients are all 802.11n STAs or lower is the likely cause of this behavior. If a WLAN with 100 802.11ac access points is configured to use 80 MHz channels, but only 40 MHz communications are seen in a particular BSS, it means that the clients in that BSS do not support 80 MHz channels. This could be because they are using older standards, such as 802.11n or lower, that do not support 80 MHz channels. Alternatively, they could be using newer standards, such as 802.11ac or ax, but have their channel width settings limited to 40 MHz or lower due to device capabilities or configuration options. In either case, the AP will adapt to the client's channel width and use only 40 MHz of the 80 MHz allocated bandwidth to communicate with them. This will reduce the potential throughput and efficiency of the WLAN.Reference:, Chapter 3, page 111; , Section 3.2

Refraction is the bending of an RF signal as it passes through a material of different density. Refraction can cause the signal to change its direction and angle of arrival. For example, when a light beam passes from air to water, it bends because of the difference in the refractive index of the two mediums.Similarly, when an RF signal passes from one medium to another, such as from air to glass, it can bend due to the change in the dielectric constant of the materials12.Reference:1: CWNA-109 Official Study Guide, page 672:Refraction