Computer Networks · free preview

Quality of Service

Some applications cannot adapt to whatever bandwidth the network happens to offer, so quality of service begins with a taxonomy, elastic applications stretch with delay while real-time ones break, then asks flows to describe themselves with token bucket parameters, rate and depth, and builds guarantees two ways, integrated services reserving per-flow state hop by hop with a receiver-initiated signaling protocol and admission control, elegant but crushed by its own state, and differentiated services marking packets at the edge into classes with per-hop behaviors, expedited forwarding for the latency-critical and assured forwarding with graded drop precedence, trading per-flow promises for core routers that stay simple.

1. Who Needs Guarantees

Who Needs Guarantees

2. Describing a Flow

Describing a Flow

3. The Grand Reservation

The Grand Reservation

4. Classes Instead of Contracts

Classes Instead of Contracts

5. Elastic and not

Which applications are called elastic, and why?

6. The bucket's arithmetic

A flow is shaped by a token bucket with rate r=1r = 1 MB/s and depth B=5B = 5 MB. What is the most it can send in a 10-second interval?

7. Why the receiver asks

In integrated services signaling, why does the receiver rather than the sender initiate the reservation?

8. What killed the grand reservation

Why did per-flow integrated services fail to deploy in the Internet core?

9. The edge-core split

In differentiated services, where do classification, metering, and policing happen?

10. Two behaviors

How do expedited forwarding and assured forwarding differ?

11. The shaping pair

A token bucket characterizes a flow with which two parameters?

12. The backward request

In integrated services signaling, senders distribute path messages downstream while which party sends reservation messages upstream?

13. The soft expiry

Integrated services keeps reservations as what kind of state, refreshed periodically and removed silently when unrefreshed?

14. The per-hop name

Differentiated services defines the treatment interior routers give marked packets as what behaviors?

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