QoS Network Toolkit

Quality of Service
Quality of service (QoS) is an often-used and misused term that has a variety of meanings. In
this book, QoS refers to both Integrated Services (IntServ) and Differentiated Services (DiffServ).
Although the two mechanisms greatly differ, the basic goal of IntServ and DiffServ is to achieve
the bandwidth and latency needed for a particular application.
DiffServ is typically used on large networks to classify the appropriate level of QoS a particular
stream or group of traffic from an individual or corporation requires. This is done via setting the
Type of Service (ToS) field or DiffServ Code Point (DSCP).
IntServ is typically used to ensure that the specific flow of traffic is going to receive the
appropriate level of QoS across the entire network before sending that traffic. This is typically
achieved using the Resource ReSerVation Protocol (RSVP).
Various tools are available to achieve the necessary QoS for a given user and application. This
chapter discusses these tools, when to use them, and potential drawbacks associated with some
of them.
It is important to note that the tools for implementing these services are not as important as the
end result achieved. In other words, do not focus on one QoS tool to solve all your QoS
problems. Instead, look at the network as a whole to determine which tools, if any, belong in
which portions of your network.
Keep in mind that the more granular your approach to queuing and controlling your network,
the more administrative overhead the Information Technology (IT) department will endure. This
increases the possibility that the entire network will slow down due to a miscalculation.