Efficient control-channel multifailure management mechanism in GMPLS-based optical networks Raül Muñoz, Ricardo Martínez, and Gabriel Junyent Centre Tecnològic de Telecomunicacions de Catalunya (CTTC) Parc Mediterrani de la Tecnologia, Avenida Canal Olímpic s/n 08860 Castelldefels, Spain raul.munoz; ricardo.martinez; gabriel.junyent@cttc.es Received January 1, 2006; revised August 29, 2006; accepted September 8, 2006; published November 17, 2006 Doc. ID 67651 In generalized multiprotocol label switching (GMPLS) architecture, the con- trol channels between each pair of optical nodes are not forced to use the same physical link as the data/transport channels. The problem arises when, due to the fact of allowing the control channels to be physically diverse from the as- sociated data links, there may not be any active control channels available while data channels are still in use. Control-channel faults should not have a service impact on the existing connections; that is, a link that is carrying data traffic must not be torn down because the control channel is no longer avail- able. But, due to the lack of the control channel, the active traffic that is using the data link may no longer be guaranteed with the same level of recovery service (protection or restoration). Under these circumstances the link must be considered to be in a degraded state. This means that routing and signaling should be notified that new connections are not accepted and the link is ad- vertised with no unreserved resources. For this purpose, here we propose a control-channel multifailure management mechanism involving routing, sig- naling, and link management with extended GMPLS-based protocol exten- sions to keep the same level of service (in terms of provisioning and recovery) when a link is in the degraded state. © 2006 Optical Society of America OCIS codes: 060.4250, 060.0060, 060.2330, 060.4510. 1. Introduction It is widely accepted that future optical transport networks are addressed to cope with the accelerating growth of (IP) data traffic as well as to support the new emerging net- work requirements such as real-time and flexible provisioning, multiple levels of qual- ity of service (QoS), and required network survivability. The recent advents of all- optical (transparent) switching devices such as reconfigurable optical add–drop multiplexers (R-OADMs) and optical cross-connects (OXCs) allow one to take full advantage of the huge bandwidth capacity provided by dense wavelength-division multiplexing (DWDM) technology. This is motivated by the fact that expensive optical–electronic–optical (OEO) transponders are no longer used in switching opera- tions, thereby eliminating the well-known electronic bottleneck [1]. On the other hand, there is a general consensus in the industry on using an optical control plane for providing intelligent mechanisms in the optical transport network. The optical control plane represents a common set of functions and interconnection mechanisms (e.g., signaling and routing) to dynamically establish optical connections (i.e., light paths), with a required level of QoS. In the context of wavelength-routed networks, the automatically switched optical network (ASON) standard [2], issued by the Inter- national Telecommunication Union in late 2001, describes the main architecture of this control plane to deal with the automatic setup, maintenance, and deletion of light paths. Furthermore, the Internet Engineering Task Force (IETF) standardized in 2004 a feasible realization of the ASON control plane through the utilization of gener- alized multiprotocol label switching (GMPLS) technology [3], which involves functions and protocols such as signaling (e.g., resource reservation protocol traffic engineering, RSVP-TE), routing (e.g., open shortest path first traffic engineering, OSPF-TE), and link management (e.g., link management protocol, LMP). In the context of the GMPLS architecture, two independent networks are used for the transmission and/or exchanging of both data and control information. These net- works are referred to here as the transport plane and the control plane respectively. Vol. 5, No. 12 / December 2006 / JOURNAL OF OPTICAL NETWORKING 1013 1536-5379/06/121013-15/$15.00 © 2006 Optical Society of America