hardMultiple ChoiceObjective-mapped
220-1201 Practice Question: A company uses a cloud-based VoIP service, and…
A company uses a cloud-based VoIP service, and users report intermittent call drops and poor audio quality. Network monitoring shows high jitter and packet loss. Which service is most likely contributing to the problem?
⚠ Common exam trap
Note the distinction between application-layer issues (SIP overload, DNS) and transport/network-layer issues (jitter, loss). Candidates often mistakenly attribute packet-level symptoms to server overload rather than missing QoS.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The network is not prioritizing VoIP traffic via QoS.
High jitter and packet loss directly degrade real-time VoIP traffic, causing call drops and poor audio. QoS (Quality of Service) mechanisms like DiffServ or 802.1p prioritize voice packets over other traffic, ensuring low latency and consistent delivery. Without QoS, the network treats VoIP packets the same as bulk data, leading to the reported symptoms.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The DHCP server is leasing IP addresses with a short lease time.
Why it's wrong here
A short DHCP lease time primarily increases network traffic related to IP address renewals and re-acquisitions. While this can add some overhead to the network, it typically does not directly cause real-time issues like jitter or packet loss during an active VoIP call, as the IP address is already assigned and stable for the duration of the established communication. The impact is more on initial connection or re-connection rather than ongoing call quality.
- ✗
The DNS server is responding slowly to queries.
Why it's wrong here
A slow DNS server primarily impacts the initial setup phase of a VoIP call, as it delays the resolution of hostnames to IP addresses for SIP servers or other call components. Once a call is successfully established and the necessary IP addresses are resolved, ongoing DNS queries are generally not required for the real-time media stream. Therefore, slow DNS would not contribute to jitter or packet loss during an active, ongoing conversation.
- ✗
The SIP server is overloaded with registration requests.
Why it's wrong here
An overloaded SIP server primarily affects the ability of VoIP endpoints to register with the system or initiate new calls, potentially leading to registration failures or significantly delayed call setup. However, once a call is successfully established, the SIP server's role in the real-time media path, which carries the actual voice data (RTP stream), is minimal. Consequently, an overloaded SIP server would not directly cause jitter or packet loss on an already active VoIP conversation.
- ✓
The network is not prioritizing VoIP traffic via QoS.
Why this is correct
Without Quality of Service (QoS) mechanisms implemented on the network, real-time VoIP traffic is treated identically to all other data traffic, such as file transfers or web browsing. This lack of prioritization means that during periods of network congestion, VoIP packets can be delayed, reordered, or dropped as they compete for limited bandwidth. This directly leads to audible symptoms like jitter and packet loss, severely degrading call quality during active conversations.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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