CDCS Quality Of Service

Quality of Service or QoS refers to traffic control mechanisms that help differentiate performance based on factors like application, network operator requirements, and traffic aggregates.

Why is QoS necessary?

1. It is needed for applications that run in real-time.
2. It is needed in video and audio conferencing as it requires bounded delay.
3. It is needed in video and audio streaming.

The requirements of QoS are as follows:

* Jitter or Delay variation

Solutions to QoS

Types of QoS solutions are as follows:

1. Stateless solutions
2. Stateful solutions

Stateless solutions:

Routers do not maintain a fine grain state about the traffic, it makes it scalable and robust. But it does not guarantee delay or performance in applications, making it a weak service.

Stateful solutions:

Routers maintain a per-flow state ensuring powerful services such as high resource utilization, protection and is less scalable and robust.

Integrated Services or IntServ

It is an architecture that guarantees QoS in IP networks. It relies on resource reservation and the network whether to admit or deny a new call setup request.

The components of IntServ QoS are as follows:

1. Resource reservation
2. QoS-sensitive scheduling
3. QoS-sensitive routing algorithm
4. QoS-sensitive packet discard strategy

RSVP internet signalling

It is used to create a distributed reservation state which is initialized by the receiver, it also scales for multicast and needs to be refreshed otherwise it results in a soft state as the reservation times out.


It is a stateful solution in which every flow does not mean a different state. It reduces state services. It maintains a state only for larger granular flows instead of end-to-end flows to solve the difficulties of IntServ and RSVP.