Free CWNP CWDP-305 Practice Exam with Questions & Answers

In Voice over WLAN (VoWLAN) deployments, it's crucial to differentiate between various types of voice-related traffic to ensure optimal Quality of Service (QoS).Real-Time Protocol (RTP) carries the actual voice payload, while control protocols like RTCP manage session control and quality feedback.Assigning distinct priority levels to these traffic types allows the network to prioritize voice payloads appropriately while still handling control traffic efficiently.

Comprehensive and Detailed Explanation:

Real-Time Protocol (RTP) is used for delivering audio and video over IP networks. Excessive retransmissions of RTP frames indicate that packets are being lost or corrupted, prompting the sender to resend them. To mitigate this, the transmitting station may lower its data transmission rate to improve reliability, which can adversely affect the quality of the voice or video stream.

Elevator shafts and similar structures can create RF “dead zones” due to their highly attenuating materials like metal. In such cases, simply increasing power or gain typically does not solve the issue due to shadowing. The recommended approach is to move APs or install additional APs on the obstructed side.

From CWDP-305:

“Obstructions such as elevator shafts may require re-positioning or the addition of APs to ensure proper coverage. These obstructions can block RF propagation regardless of transmit power or antenna gain.”

— Reference: CWDP-305 Official Study Guide, Post-Design ValidationandTroubleshooting Chapter

Comprehensive and Detailed Explanation:

Increasing capacity in a coverage-based wireless network involves optimizing the network to handle more clients and traffic efficiently. The recommended techniques include:

A. Maximize airtime usage by disabling lower data rates:Disabling lower data rates (e.g., 1 Mbps, 2 Mbps) reduces the time the medium is occupied by slower transmissions, thereby increasing overall network efficiency and capacity.

B. Add additional APs and use directional antennas:Deploying more access points (APs) with directional antennas helps in segmenting the coverage area, reducing co-channel interference, and increasing capacity by allowing more simultaneous transmissions in different directions.

D. Lower power on the access points and, after careful planning, add more APs:Reducing the transmit power of APs minimizes overlap and interference between cells. After careful planning, adding more APs ensures coverage continuity and increases capacity by distributing the load among more APs.

C. Turn up power on the access points:Increasing the transmit power can lead to excessive overlap between cells, causing interference and reducing overall network capacity. Therefore, this is not a recommended practice for increasing capacity.

In WLAN design software, defining different “requirement areas” allows the designer to assign distinct RF and performance requirements to different parts of the floor plan. For instance, a voice-critical conference room may require –67 dBm minimum signal strength and a specific SNR, whereas a storage area might only require basic coverage.

From CWDP-305:

“Requirement areas allow WLAN designers to set different RF performance targets such as minimum signal strength, SNR, and data rate for specific parts of the deployment area. This enables tailored design strategies.”

— Reference: CWDP-305 Official Study and Reference Guide, Chapter on Wireless Design Process

802.11r Fast Transition (FT) defines two methods to facilitate quick and secure roaming between access points:

Over-the-Air (OTA): The client communicates directly with the target AP to perform the authentication exchange during roaming.

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Over-the-DS (Distribution System): The client communicates with the current AP, which then relays the authentication information to the target AP over the wired network.

Both methods aim to reduce latency during the roaming process, ensuring seamless connectivity for applications sensitive to delays, such as VoIP.

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Comprehensive and Detailed Explanation:

For Voice over IP (VoIP) over WLAN, seamless roaming is critical to maintain call quality. To achieve this:

D.Ensuring that at least two access points (APs) are visible with adequate signal strength from any location allows client devices to roam between APs without dropping the connection. This overlap facilitates smooth handoffs and maintains call continuity.

A.While measuring cell overlap is useful, the key is to design the network to provide the necessary overlap, not just measure it.

B.Increasing output power can lead to larger cells but may cause interference and reduce the number of available channels, which is counterproductive in dense environments.

C.Higher gain antennas focus the signal, which may not provide the desired omnidirectional coverage needed for consistent overlap.

Comprehensive and Detailed Explanation:

The 2.4 GHz band has only three non-overlapping channels: 1, 6, and 11.Using other channels can lead to overlapping and interference.To prevent this, the automatic channel assignment settings should be configured to use only channels 1, 6, and 11, ensuring minimal overlap and optimal performance.

If a persistent source of interference cannot be removed, the best course of action is to design around it—usually by changing channels to avoid the affected frequencies. This minimizes the impact on WLAN operation while still coexisting with the interfering device.

From CWDP-305:

“If interference is detected during post-deployment validation and cannot be mitigated by removal, channel reallocation is the most effective way to work around the problem without affecting WLAN integrity.”

— Reference: CWDP-305 Official Study Guide, Post-Design ValidationandTroubleshooting

In Wi-Fi networks, the 802.11e amendment introduces Quality of Service (QoS) by defining Access Categories (ACs) to prioritize different types of traffic.The AC_VO (Voice) category is designated for voice traffic, which requires low latency and jitter.To maintain QoS across both wireless and wired networks, it's essential to map these categories to appropriate Differentiated Services Code Point (DSCP) values.

The AC_VO category corresponds to the Expedited Forwarding (EF) DSCP value, which is 46.This mapping ensures that voice traffic receives high priority treatment throughout the network, minimizing delays and ensuring call quality.