•  Multi-entity link-sharing:- A link may be purchased and used jointly by several organizations, government agencies etc. They may wish to insure that when experiencing overload the link is shared in a controlled way.Also these agencies want that when the link is underloaded, any one of the entities can utilize all the idle bandwidth.
• Multi-protocol link-sharing:- In a multi-protocol Internet, it may be desired to prevent one protocol family from overloading the link and excluding the other families. This is important because different families may have different methods of detecting and responding to congestion, and some methods may be more aggressive than others.This could lead to a situation in which one protocol backs off more rapidly than another under congestion, and ends up getting no bandwidth. Explicit control in the router may be required to correct this.

 
• Multi-service sharing:- Within a protocol family such as IP, an administrator might wish to limit the fraction of bandwidth allocated to various service classes.

 

As cited in [RFC 1633],in many audio and video streams , some packets are more valuable than others. Hence a "preemptible" packet service, is introduced whereby some of the packets within a flow could be marked as preemptible.When  the network is in danger of not meeting some of it's quantitative service commitments, it can use the preemptibility option and discard the packet thereby reducing the delays of the not-preempted packets.

This is called as "usage feedback" [RFC 1633]  to prevent abuse of the network resources.

2.1.7 Reservation Model:-

This describes as to how an application negotiates for a QoS level. The simplest model is that the application asks for a particular QoS and the network either grants it or refuses.Many applications will be able to get acceptable service from a range of QoS levels , or more generally, from anywhere within some region of the multidimensional space of a flowspec.