Which of the following service model can provide end-to-end QoS service, but the scalability is not good?

Question

Options

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

• A
  18% (5)
• B
  71% (20)
• C
  4% (1)
• D
  7% (2)

Explanation

IntServ (Integrated Services) uses the RSVP protocol to reserve bandwidth and resources on every router along the end-to-end path for each individual flow, which guarantees QoS from source to destination. The fatal scalability problem is that every router must maintain per-flow state, and as the number of flows grows (especially in large backbone networks), routers become overwhelmed with signaling and state management.

Best Effort (A) provides no QoS guarantees whatsoever - packets are simply delivered as resources allow with no reservation or prioritization mechanism. FIFO (C) is a packet-scheduling/queuing discipline, not a QoS service model, and it treats all packets identically in arrival order with no differentiation. DiffServ (D) is the model designed specifically to address IntServ's scalability problem - it marks packets with DSCP codes at the network edge and applies per-hop behaviors at each router, eliminating per-flow state and scaling well to large networks, but it does not provide strict end-to-end guarantees.

Memory tip: Think "IntServ = Intensive reservation" - it intensively reserves resources for every flow end-to-end (great quality, poor scale), while DiffServ = "Differentiated but not dedicated" - it differentiates traffic classes without reserving per-flow resources (good scale, no strict guarantee).

No community discussion yet for this question.