Custom queuing prioritizes multiprotocol traffic. A maximum of 16 queues can be built with custom
queuing. Each queue is serviced sequentially until the number of bytes sent exceeds the configurable
byte count or the queue is empty. One important function of custom queuing is that if SNA traffic
uses only 20 percent of the link, the remaining 20 percent allocated to SNA can be shared by the
other traffic.
Custom queuing is designed for environments that want to ensure a minimum level of service for all
protocols. In today’s multiprotocol internetwork environment, this important feature allows
protocols of different characteristics to share the media.
Weighted Fair Queuing
Weighted fair queuing is a traffic priority management algorithm that uses the time-division
multiplexing (TDM) model to divide the available bandwidth among clients that share the same
interface. In time-divisionmultiplexing, each client is allocated a time slice in a round-robin fashion.
In weighted fair queuing, the bandwidth is distributed evenly among clients so that each client gets
a fair share if every one has the same weighting. You can assign a different set of weights, for
example through type-of-service, so that more bandwidth is allocated.
If every client is allocated the same bandwidth independent of the arrival rates, the low volume traffic
has effective priority over high volume traffic. The use of weighting allows time-delay-sensitive
traffic to obtain additional bandwidth, thus consistent response time is guaranteed under heavy
traffic. There are different types of data stream converging on a wire, as shown in Figure 2-7.
