viewed as secondary in importance to business operations or are highly asynchronous in nature. These
applications include Netmeeting and messaging
normal enterprise operations. While some of these applications might be interactive, no bandwidth
guarantees are required. Perhaps the best examples of these types of application are E-mail and generic
Internet browsing.
anything to do with the enterprises' business. These applications are typically highly delay and drop
insensitive, and often the executions of such applications span over hours. Therefore, these applications
can be given a higher-drop preference to prevent them from robbing bandwidth away from best-effort
applications. Examples of less-than-best-effort of traffic include large file transfers, backup operations,
and peer-to-peer entertainment-media swapping applications (like Napster, KaZaa, Gnutella).
these in hopes of indirectly improving available bandwidth to other applications. With this reactive
approach, bandwidth is monopolized by unimportant applications until users of important applications
complain enough to warrant investigation into the cause by the IT or networking departments. After
time, the investigations reveal the culprit application, which is subsequently policed. Performance of the
important applications will likely improve, but only until another lesser-important, bandwidth-intensive
application emerges. In this approach, the bandwidth-limiting policies will become increasingly
complex to administer and will require more CPU overhead to enforce as their complexity grows.
applications (in their respective orders) and provision a best-effort default class. After these protective
policies are in place, optional policing policies can be overlaid for less-than-best-effort traffic. However,
the implementation of policing policies creates a static limit that may not always be desirable. For
example, data backups, which usually occur overnight, often make use of the additional bandwidth that
is available during non-peak hours. With policing policies, the unused bandwidth would not be available,
which could cause the backup process to carry over into morning work hours. Therefore, increasing the
drop preference of less-than-best- effort traffic (instead of using strict policing policies) is a more
efficient use of available bandwidth.
With voice and video, the need for QoS is relatively objective and obvious. However, this is not the case
with data applications.
select few applications to these classes opens up a variety of subjective non-technical issues. This is
because the enterprise is left to subjectively rank their applications in relative priority. This process is
usually very politically and organizationally charged and quite often takes more time to complete than
the actual technical portion of a QoS implementation.
applications within the enterprise, otherwise QoS rollout projects could get derailed when disagreements
arise over which applications are the more important.