📝 Proxy firewall in network security (11 MCQs)
📖 From Data Communication and Networks • 32. Internet Security • 11 questions available
What is Proxy firewall in network security?
A proxy firewall operates at the application layer by intercepting all traffic and acting as an intermediary between clients and servers, inspecting full application content and enforcing granular security policies before forwarding legitimate requests.
📝 All Proxy firewall in network security MCQs
Q1. Which of the following best describes the purpose of a metafile in the second approach to streaming stored audio/video?
📖 Explanation: The metafile does not hold the media itself; it carries descriptive data like the file’s URL, size, format, and timing information. The media player reads this metadata to locate and stream the actual audio/video file, enabling on‑demand access without embedding the full content.
Q2. If TCP retransmits lost segments causing additional delay, which streaming approach is most likely to suffer noticeable playback interruption?
📖 Explanation: TCP’s retransmission adds latency, which is most problematic when the whole file must be downloaded before playback begins. In the first approach the client must receive the complete file via HTTP/TCP before the media player can start, so any retransmission directly extends the wait time, leading to perceptible interruptions.
Q3. Compare the latency experienced by users in the first approach (direct download) versus the second approach (metafile then media player). Which statement is accurate?
📖 Explanation: When a metafile is retrieved first, the media player obtains the URL quickly and can begin streaming portions of the audio/video while the rest of the file continues to download. This overlap shortens the waiting period before playback, unlike the first approach where playback must wait for the entire file to arrive, resulting in higher perceived latency.
Q4. How does a proxy firewall positioned between client and server impact the third approach that uses a dedicated media server?
📖 Explanation: A proxy firewall can be configured to recognize streaming protocols such as RTSP (often carried over UDP/TCP on port 554). By permitting this traffic and simultaneously blocking standard HTTP requests, the firewall enables the media server to deliver continuous streams while preventing non‑streaming HTTP downloads, thereby shaping traffic according to security policy.
Q5. Why is TCP considered unsuitable for large continuous audio/video streams compared to protocols like UDP?
📖 Explanation: TCP guarantees reliable delivery by retransmitting lost packets, which adds variable delay. For real‑time audio/video, this delay can cause buffering or stutter, degrading the user experience. Protocols like UDP forego retransmission, delivering packets with minimal latency, making them preferable for continuous streaming where occasional loss is tolerable but timely arrival is critical.
Q6. Which advantage does using a dedicated media server (third approach) have over a web server with a metafile (second approach)?
📖 Explanation: A dedicated media server can employ protocols such as RTP/RTSP that support features like adaptive bitrate, jitter buffering, and real‑time control, which are not available through simple HTTP file transfers. This specialization allows smoother playback, efficient bandwidth usage, and better handling of large media files compared with a generic web server that only serves static files and metafiles.
Q7. Design a proxy firewall rule set that permits on‑demand streaming of stored video while preventing users from downloading the entire file. Which combination best achieves this?
📖 Explanation: By allowing HTTP range (byte‑range) requests, the client can retrieve small segments of the video for buffering while the firewall blocks requests that ask for the whole file in a single GET. This selective permission enables streaming playback yet stops users from obtaining the complete file in one transfer, balancing accessibility with content protection.
Q8. If a proxy server caches the first 10 seconds of a video file in the first approach, what is the most likely effect on user experience?
📖 Explanation: When the proxy already holds the initial segment, the client can retrieve it instantly without waiting for the origin server. This reduces the time needed before playback can start, leading to a quicker response and smoother user experience, especially on slower connections where fetching the first bytes would otherwise dominate the startup delay.
Q9. How does TCP behavior differ when a client retrieves a metafile versus when it retrieves the actual audio/video file?
📖 Explanation: Metafiles are typically tiny, so any lost packets are quickly retransmitted with minimal effect on overall latency. In contrast, large audio/video files generate many packets; loss of any segment triggers TCP’s retransmission algorithm, potentially causing noticeable delays and jitter that can disrupt continuous playback if not managed by buffering strategies.
Q10. In on‑demand streaming, what buffering strategy must the client implement to ensure smooth playback despite variable network speed?
📖 Explanation: The client should initially download a short segment (a few seconds) to create a playback buffer, then continue fetching subsequent data while monitoring network conditions. If speed drops, the buffer compensates, preventing interruptions. This adaptive buffering balances latency and continuity, allowing seamless viewing even when bandwidth fluctuates.
Q11. If the URL contained in a metafile points to a resource blocked by the proxy firewall, what will the media player experience?
📖 Explanation: When the firewall denies access to the URL, the media player cannot establish a connection to the server hosting the audio/video file. Consequently, it reports an error (e.g., “Unable to locate media”) and aborts playback, as it has no alternative source to retrieve the requested content.