Network managers must be prepared for increasing amounts of traffic,
requiring more bandwidth than is currently available. This is especially
important when dealing with Voice traffic. Almost any network can take
advantage of QoS for optimum efficiency, whether it is a small corporate
network, an Internet service provider (ISP), or an enterprise network. QoS is
the application of features and functionality required to actively manage and
satisfy networking requirements of applications sensitive to loss, delay, and
delay variation (jitter). QoS allows preference to be given to critical
application flows for the available bandwidth. QoS tools enable manageability
and predictable service for a variety of networked applications and traffic
types in a complex network.
The Cisco IOS implementation of QoS software
provides these benefits:
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Priority access to resources – QoS allows administrators to control
which traffic is allowed to access specific network resources such as
bandwidth, equipment and WAN links. Critical traffic may take possession of a
resource by dropping low-priority packets.
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Efficient management of network resources – If network management
and accounting tools indicate that specific traffic is experiencing latency,
jitter, and packet loss, then QoS tools can be used to adjust how that traffic
is handled.
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Tailored services – The control provided by QoS enables ISPs to
offer carefully tailored grades of service differentiation to their customers.
For example, a service provider can offer one service level agreements (SLAs)
to a customer website that receives 3000 to 4000 hits per day and another to a
site that receives only 200 to 300 hits per day.
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Coexistence of mission-critical applications – QoS technologies
ensure that mission-critical business applications receive priority access to
network resources while providing adequate processing for applications that are
not delay sensitive. Multimedia and voice applications tolerate little latency
and require priority access to resources. Other delay-tolerant traffic
traversing the same link, such as SMTP over TCP, can still be adequately
serviced.