Inter - Semester 2011 Handout 13 1 5 Traffic Grooming inWavelength - RoutedWDMNet

In the last chapter, we assume that each source-destination (s-d) pair has its taffic demand equal to an integer multiple of wavelength unit. Accordingly, supporting such traffic in transparent wavelength division multiplexing (WDM) networks can be done by establishing lightpaths between s-d pairs. In addition, these established lightpaths will be fully utilized. In this chapter, we allow for subwavelength traffic. For example, the traffic of an s-d pair may be equal to 0.3 wavelength unit. In this type of scenario, a single lightpath may carry multiple traffic streams from different s-d pairs. This multiplexing of several traffic streams onto a common lightpath is called traffic grooming, which is necessary for efficient wavelength channel usages. Consequently, the traffic of an s-d pair may have to flow on multiple lightpaths so that efficient traffic grooming can be performed at intermediate switching nodes. We shall first discuss traffic grooming in backbone WDM networks. Later on, we shall consider traffic grooming in ring networks which are commonly used for metropolitan WDM networks. We focus on static traffic, with some discussion on dynamic traffic given in the final section.