Very interesting results are presented in this paper about service differentiation in the IEEE 802.11 media access control (MAC) sub-layer. The authors analyze four mechanisms in order to evaluate their ability to provide service differentiation. The proposed mechanisms take into account different operational aspects of the IEEE 802.11 MAC sub-layer standard, by considering contention window variation, CWmin differentiation, DCF Inter-Frame Space (DIFS) differentiation, and the maximum frame length allowed by each wireless terminal.

The simulation study finds that DIFS differentiation and maximum frame length mechanisms are well suited to providing service differentiation, both for transmission control protocol (TCP) and user datagram protocol (UDP) flows. The paper also analyzes the effect of the access point in differentiating services, which is very important when TCP flows are considered.

This is a very interesting paper because it addresses an interesting problem, and, most importantly, because it presents an engineering point of view of the problem. The paper presents a set of mechanisms to differentiate services. Then, it presents simulation results, and interprets these results from the mathematical point of view. And, finally, it helps in making engineering decisions. The authors recommend the use of the DIFS mechanism for service differentiation in wireless local area networks (LANs).