Lesson 10: Understanding Quality of Service

What Is QoS? | QoS Building Blocks | QoS in Action

Example: No Quality of Service

Here’s an example of how RSVP works. Let’s first look at what the problem would be without RSVP.

In this example, the video traffic still gets through, but it is impacted by a large file transfer in progress. This causes a negative effect on the quality of the video and the picture comes out all jittery.
What we need is a method to reserve bandwidth from end-to-end on a per-application basis. RSVP can do this.

This figure explains how RSVP actually works.

RSVP reserves bandwidth from end-to-end on a per-application basis for each user. This is especially important for delay-sensitive applications, such as video.

As shown here, with RSVP, the client’s application requests bandwidth be reserved at each of the network elements on the path. These elements will reserve the requested bandwidth using priority and queuing mechanisms.
Once the server receives the OK, bandwidth has been reserved across the whole path, and the video stream can start being transmitted. RSVP ensures clear video reception.

The good news is that RSVP is becoming widely accepted by industry leaders, such as Microsoft and Intel, who are implementing RSVP support in their applications. These applications include Intel’s Proshare and Microsoft’s NetShow. To provide support on a network, Cisco routers also run RSVP.

End-to-End QoS

End-to-end QoS is essential. Following image provides a context for the different QoS features we looked at.

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