There are many video conferences in large companies, and QoS generally adopts the service model.

Question

Options

• ABest Effort model
• BIntServ model
• CFIFO model
• DDiffServ model

• A
  7% (2)
• B
  3% (1)
• C
  77% (23)
• D
  13% (4)

Explanation

Important note: the stated correct answer (C) appears to be incorrect. FIFO (First In, First Out) is a packet queuing discipline, not a QoS service model - it treats all packets equally in arrival order with no priority differentiation, making it unsuitable as a QoS strategy. For large companies running many video conferences, D (DiffServ) is the standard correct answer.

Why DiffServ is correct: Large-scale enterprise networks use the Differentiated Services model because it classifies traffic into priority classes (marking packets with DSCP values at the network edge) and handles them accordingly throughout the network - giving real-time video traffic low latency and priority without per-flow signaling overhead.

Why the distractors are wrong:

• A (Best Effort): No QoS guarantees at all; video/audio quality would be unpredictable under load.
• B (IntServ): Provides strong per-flow guarantees via RSVP reservation, but requires every router to maintain per-flow state - it does not scale to large networks with many simultaneous video conferences.
• C (FIFO): A scheduling mechanism, not a QoS service model; it provides no traffic differentiation.

Memory tip: Think "DiffServ = Different lanes on a highway"* - scalable for large traffic volumes, while IntServ = toll-booth reservations per car (works small-scale, breaks down at scale). For large enterprises, always choose DiffServ.

If your course materials explicitly list C as correct, I'd recommend double-checking your textbook - this appears to be a question with an erroneous answer key.

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