Key Points of a Scheme Design Problem for Multilayer Survivability

in Optical Networks


 Çiçek Çavdar*,  Feza Buzluca**

*Department of Computer Science, ** Department of Computer Engineering

     Istanbul Technical University,
Faculty of Electrics and Electronics, Maslak,
Istanbul, Turkey.           





Network survivability ensuring service continuity at an affordable cost is important for wavelength-division-multiplexing (WDM) optical networks. Because in a WDM optical network, the failure of network elements (e.g., fiber links and cros connects) may cause the failure of several optical channels, thereby leading to large data losses. This study examines different approaches to recover a mesh based WDM optical network in case of such failures. In this paper we intend to review the most widespread strategies up to now proposed to manage survivability in WDM networks and state the key points of a survivability scheme design.

We explore survivability approaches in different layers of the network and compare them with each other before we focus on survivability in IP/MPLS-over-WDM networks. We state  the main problems of recovery in IP/MPLS and WDM layers separately and compared these layers, discussing their advantages and drawbacks. Lastly we designed a recovery strategy that takes different service classes of applications and resource utilization in a cost effective manner into account.

We take advantage of MPLS to differentiate traffic as two different service classes. The high priority class is characterized by tight delay and recovery time requirements. In our scheme, we used a multilayer survivability approach so that IP/MPLS and optical layer are used together for different types of traffic. The WDM layer recovery is used to recover the failure of high priority class traffic quickly. On the other hand we utilize network resources efficiently by using a dynamic, upper layer scheme  (restoration in IP/MPLS layer) for normal class traffic failures.



Keywords : layered protection and restoration, multilayer  survivability, optical transport network, survivability in WDM networks, survivability scheme design