Media and QoS

Users at a branch site report choppy, robotic audio only on calls that traverse the WAN during business hours; internal branch-to-branch calls are clear. The WAN router's egress interface shows increasing output drops in the default queue during peak periods, and a packet capture shows RTP packets arriving with high jitter and occasional gaps. DSCP markings on the RTP packets are correctly set to EF at the phones and are preserved end to end. What is the most likely root cause and appropriate fix?

A company deploys a Cisco Unified Border Element (CUBE) to connect their on-premises CUCM cluster to a SIP service provider. After configuration, outbound calls connect and both parties hear ringback, but once the call is answered there is complete two-way silence. SIP signaling completes normally, and 'show voip rtp connections' on the CUBE shows local and remote RTP entries being created for each call. A packet capture on the service provider-facing interface shows outbound RTP packets leaving the CUBE, but no inbound RTP is ever received. What is the MOST likely cause?

A network engineer is building an LLQ policy on a WAN router to protect UC traffic. Voice RTP is classified into class VOICE and video conferencing RTP into class VIDEO. During periods of congestion, users report that voice remains clear but the video stream occasionally freezes even though there is available bandwidth on the link. Reviewing the policy-map, the engineer sees the VOICE class uses 'priority 1000' and the VIDEO class uses 'bandwidth 2000'. Which statement best explains the behavior and the correct design principle?

You are configuring LLQ on a WAN edge router to prioritize voice RTP traffic that arrives from the LAN already marked with the correct DSCP value by trusted IP phones. You want to build a class map that identifies this voice bearer traffic so it can later be placed into the priority queue. Which class-map configuration correctly matches the voice media traffic?

A network engineer is configuring LLQ on a WAN edge router that must prioritize voice while guaranteeing minimum bandwidth to two data classes (business-critical and scavenger) during congestion. Voice is already placed in a strict-priority queue with the 'priority' command. For the business-critical and scavenger classes, the engineer wants each class to receive a proportional share of the bandwidth that remains after the priority queue is serviced, expressed as a percentage. Which command should be applied within those two class configurations in the policy map?

During a network audit you review the following QoS policy applied outbound on a WAN interface: a class-map matches voice RTP (DSCP EF), and the policy-map assigns it 'priority 512'. The circuit is congested during peak hours, and users report that after a large batch of new calls connect, some active calls develop choppy audio while others sound fine. Signaling and video classes are unaffected. What is the most likely explanation for this behavior?

A network engineer is configuring LLQ on a WAN-edge router to protect voice media traversing a congested serial link. Voice RTP has been marked EF (DSCP 46) by the IP phones, and call-signaling traffic is marked CS3 (DSCP 24). The engineer needs to guarantee low-latency, prioritized treatment for the voice media specifically, reserving 1000 kbps for it. Which configuration element correctly provides strict priority queuing for the voice media within the LLQ policy?

Users at a branch site report that on some outbound PSTN calls through a centralized CUBE, the called party can hear the branch user, but the branch user hears nothing. Signaling completes normally and calls stay connected. A packet capture at the branch phone shows outbound RTP leaving the phone, but no inbound RTP arriving. The same phones work fine on internal calls. What is the MOST likely cause of this one-way audio?

Users report that when an internal IP phone calls a remote site over a SIP trunk, the internal user can hear the remote party clearly, but the remote party hears nothing from the internal user. Signaling completes normally and the call stays connected. RTP statistics on the internal phone show packets being transmitted but zero packets received on the far end. What is the MOST likely cause of this one-way audio condition?

A network engineer is building a QoS policy for a new Cisco UC deployment. To ensure consistency with Cisco Enterprise Medianet marking recommendations, they must apply the correct DSCP values so that voice bearer traffic and call-control signaling are each classified into their appropriate per-hop behaviors. Which DSCP marking assignment is correct for these two traffic types?

A network engineer is deploying IP phones with attached PCs on access switches. The desk PCs are re-marking their own traffic with DSCP EF to gain priority, causing voice quality degradation for the phones during congestion. The engineer wants to enforce the QoS trust boundary at the correct location so that only the phone's markings are trusted while PC markings are reset. Where should the trust boundary be established and how?

A network engineer is deploying QoS on an access switch where Cisco IP phones connect to the switchport and PCs daisy-chain behind the phones. Company policy requires that the switch never trust any markings originating from the PCs, but it must honor the phone's CoS markings for voice and signaling. Which configuration approach on the access port correctly establishes the trust boundary?

A UC engineer is deploying wireless IP phones on an 802.11 WLAN. Voice calls over Wi-Fi experience intermittent delay and jitter even though the wired core already trusts DSCP end-to-end. Which statement correctly describes a QoS consideration unique to carrying signaling and media across the wireless portion of the network?

Users on a wireless voice VLAN report choppy, garbled audio during calls, while wired phones on the same site are unaffected. RTCP statistics on the affected phones show low packet loss (0.2%) but jitter values fluctuating between 60 ms and 120 ms. The QoS policy marks voice with EF (DSCP 46) end to end, and the WLAN has WMM enabled. Which action is the MOST likely to resolve the choppy audio for the wireless users?

A network engineer is troubleshooting a persistent one-way audio problem on inbound PSTN calls that traverse a Cisco Unified Border Element (CUBE) to Cisco Unified Communications Manager. Signaling completes normally and calls connect, but the internal IP phone user can hear the PSTN caller while the PSTN caller hears nothing. Packet captures on CUBE show RTP arriving from the phone side but no RTP being forwarded toward the service provider. Which action is the most likely resolution?

A network engineer is troubleshooting intermittent voice quality complaints (choppy audio and jitter) on calls that traverse a SIP trunk between a CUCM cluster and a remote site across a QoS-enabled WAN. Signaling is stable and calls connect normally, but during periods of high data traffic the RTP streams degrade. Packet captures at the WAN edge show that the voice media packets are arriving with a DSCP value of 0 (Best Effort) instead of EF. Signaling packets are correctly marked. Which action is MOST likely to resolve the media degradation?

Users on a video endpoint report that during calls the far-end video periodically 'freezes' and displays blocky, smeared artifacts on the screen, while audio remains clear. The network team confirms that the audio and video traverse the same WAN link, and DSCP marking for video (AF41) and audio (EF) is applied correctly at the campus trust boundary. RTCP statistics from the endpoint show intermittent bursts of packet loss on the video stream only. What is the MOST likely root cause of the video artifacts?