Survivable embedding of logical topologies in WDM ring networks q Hwajung Lee a , Hongsik Choi b, * , Suresh Subramaniam c , Hyeong-Ah Choi a a Department of Computer Science, The George Washington University, Washington, DC 20052, USA b Division of Information and Communication Engineering, Hallym University, Chunchon, South Korea c Department of Elect. & Computer Engr., The George Washington University, Washington, DC 20052, USA Received 27 September 2001; accepted 8 May 2002 Abstract We consider the design of survivable logical topologies over physical WDM ring networks. The logical topology consists of the same set of nodes as the physical to- pology, and the links of the logical topology are lightpaths in the physical topology. The logical topology is said to be survivable if the failure of any single physical link does not disconnect the logical topology. In this paper, we consider the following problem. Given a logical topology with lightpath end-nodes, route the lightpaths to make the logical topology survivable if possible. Otherwise, determine and embed the minimum number of additional lightpaths to achieve survivability. Ó 2002 Elsevier Science Inc. All rights reserved. Information Sciences 149 (2003) 151–160 www.elsevier.com/locate/ins q This work was supported in part by the DARPA under grant N66001-00-18949 (co-funded by NSA), by the DISA under NSA-LUCITE contract, and by the NSF under grant ANI-9973098. * Corresponding author. Tel.: +1-202-994-4217. Currently on leave at the Department of Computer Science, George Washington University, Washington DC 20012, USA. E-mail addresses: hjlee@seas.gwu.edu (H. Lee), hongsik@seas.gwu.edu (H. Choi), suresh@ seas.gwu.edu (S. Subramaniam), choi@seas.gwu.edu (H.-A. Choi). 0020-0255/02/$ - see front matter Ó 2002 Elsevier Science Inc. All rights reserved. PII:S0020-0255(02)00252-9