Resource Sharing Requirements
The allocation of resources
is typically negotiated on a flow-to-flow basis as each flow requests admission
to the network. The quantity of primary interest in resource-sharing is
aggregate bandwidth on individual links. There are examples that are commonly
used to explain the requirement of link sharing among collective entities:
2.1.5 Packet Dropping:
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.
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.
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.
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.