d about three things: Delineating and sharing the available buffering memory among a potentially large number of queues. A packet discard mechanism. A scheduling mechanism. Buffer Management Discard Discard FIGURE 15.4 Differentiated packet treatment for QoS based on buffer management. Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. TRAFFIC MANAGERS TRAFFIC MANAGERS The last part is implemented upon the very same premises and techniques that we just discussed in the section on schedulers. Buffer space is split up among the multiple flows/queues along many approaches. The following three approaches are the most important: Complete partitioning This is one of the two extreme approaches. With it, each queue is simply allocated a fixed amount of buffer space. This is easy to implement, but not very efficient as queues that are starved for more space cannot access the potentially empty parts of the overall buffer mem- ory space. Complete sharing This is the other extreme of the spectrum. Available buffer space is fully and equally shared among the queues. No space is wasted as may be the case with complete partition- ing, but the attained degree of fairness is a problem, as any queue essentially can eat up the buffer space to the detriment of others. Sharing with minimum allocation Somewhere between the top two extreme approaches lies the method of sharing with minimum allocation. This technique preallocates some fixed minimum space to each and every queue. The rest is then fairly and equally shared among all the queues. It is known for its simplicity, efficiency, and fairness. Implementing QoS based on the differential treatment of packets is an interesting approach that tries to juggle computational resources (processing cycles and memory) to make a slew of decisions that allow a judicious compromise between the multiple and sometimes contradic