Due to its simplicity and scalability, the differentiated services (DiffServ) model is expected to be widely deployed across wired and wireless networks. Though DiffServ supporting scheduling algorithms for output-queuing (OQ) switches have been widely studied, there are few DiffServ scheduling algorithms for input-queuing (IQ) switches in the literaure. In this paper, we propose two DiffServ scheduling algorithms for DiffServ networks with IQ switches: the dynamic DiffServ scheduling (DDS) algorithm and the hierarchical DiffServ scheduling (HDS) algorithm. The basic idea of DDS and HDS is to schedule EF and AF traffic according to their minimum service rates with the reserved bandwidth and schedule AF and BE traffic fairly with the excess bandwidth. Both DDS and HDS find a maximal weight matching but in different ways. DDS employs a centralized scheduling scheme. HDS features a hierarchical scheduling scheme that consists of two levels of schedulers: the central scheduler and port schedulers. Using such a hierarchical scheme, the implementation complexity and the amount of information needs to be transmitted between input ports and the central scheduler for HDS are dramatically reduced compared with DDS. Through simulations, we show that both DDS and HDS provide minimum bandwidth guarantees for EF and AF traffic as well as fair bandwidth allocation for BE traffic. The delay and jitter performance of DDS is close to that of PQWRR, an existing DiffServ supporting scheduling algorithm for OQ switches. The tradeoff of the simpler implementation scheme of HDS is its slightly worse delay performance compared with DDS.
Przedstawiono najistotniejsze cechy modeli IntServ i DiffServ pod kątem zapewnienia jakości usług w relacji od końca do końca w sieci IP. Omówiono możliwości praktycznego zastosowania tych modeli w różnych obszarach sieci oraz zagadnienia ich współpracy. Pdjęto też próbę uporządkowania terminologii związanej z jakością usług.
EN
The article discusses the main features of the IntServ and DiffServ models as regards ensuring end-to-end quality of service guarantees. Applicability of these models in various network areas and interworking issues are also described. Consistent terminology for QoS issues is presented.
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