A scheme for guaranteeing network tunnel path (NTP). e.g., Internet Protocol (IP), service levels in optical (e.g., wavelength-division multiplex (WDM)) networks. The invention, in one embodiment, accounts for both network topology (e.g. switches, cross-connects, and links between nodes) and resource usage (e.g., available/provisioned link bandwidth and available/used wavelength paths), which information may be available from the IP and optical WDM protocol layers, in particular (i) router capacities and (ii) presence or absence of wavelength conversion capability of optical cross-connect at each node. A determination is made whether to route an arriving request for an NTP over existing topology by computing "good" routes in accordance with a defined metric, or to open a new, available optical wavelength path by provisioning nodes of the topology for, and computing "good" routes for new wavelength paths. As many requests as possible are identified without a priori information of future requests.