Photon Netw Commun (2009) 18:345–354
A survivable multicast routing mechanism in WDM optical
Hichem Ayed Harhira · Samuel Pierre
Received: 5 October 2008 / Accepted: 17 February 2009 / Published online: 10 March 2009
© Springer Science+Business Media, LLC 2009
Abstract In NextGenerationNetworks(NGN),survivabil-
ity and availability are becoming more and more key features.
Reliability gains more importance in high- capacity networks
where IP and optical technologies have converged toward a
common control plane, such as GMPLS. In most previous
research works, survivability aspects were mainly limited to
a single ﬁber failure and a few considered the differentiated
reliability concepts when routing new connection requests.
In this article, a novel survivable multicast routing mecha-
nism under SRLG constraints is proposed. We ﬁrst formu-
late the problem as an Integer Linear Programming (ILP)
model that is shown NP-Complete. We then propose a heu-
ristic algorithm that alleviates the problem’s complexity by
decomposing it into two sub-problems resolved separately.
Compared with another algorithm proposed in the literature,
our algorithm allows for higher acceptance rates even for
stringent reliability requirements.
Keywords Wavelength Division Multiplexing (WDM) ·
Shared Risk Link Group (SRLG) · Differentiated reliability ·
Survivability · Mathematical programming
As Next Generation Networks (NGN) are becoming more
and more multi-services, new mechanisms for providing a
H. A. Harhira (
) · S. Pierre
Department of Computer and Software Engineering, Ecole
Polytechnique de Montreal, CP. 6079 Succ. Centre Ville, Montreal,
QC H3C 3A7, Canada
certain level of Quality of Service (QoS) and failure resil-
ience are indispensable. In fact, in the last decade, stringent
QoS and reliability requirements have emerged due to the
overwhelming demand for real-time and multimedia appli-
cations that involve data, voice, video, telephony, IPTV, etc.
to be conveyed over the same network. In such a scenario,
optical networks embedded with the Wavelength Division
Multiplexing technology is a key feature for providing high-
capacity and cost-effective transport networks.
The physical layer in a WDM network consists of a set
of nodes interconnected by multiple optical ﬁbers. Fibers are
generally grouped and inserted into a single conduit such that
every single ﬁber can belong to different conduits, depending
on its physical length. Such ﬁbers are said to be in the same
Shared Risk Link Group (SRLG) as the failure of the conduit
results in the failure of all ﬁbers inside.
At the optical level, circuits or connections are set up
between peer Optical Cross Connectors (OXC) and named
lightpaths. Lightpaths are generally protected using either a
dedicated or a shared protection, depending on the reliability
A multitude of survivable routing mechanisms have been
proposed for WDM optical networks with SRLG constraints
[1–9]. In , Li et al. proposed a greedy heuristic for multi-
cast protection under SRLG constraints. Their algorithm con-
structs a tree from the source to the set of destinations using
the Shortest Path Tree (SPT) algorithm and computes, for
every branch, an SRLG protected path, such that the whole
tree is well protected. Before computing the protection tree,
the links’ metrics are altered in order to take into account the
backup resources sharing. In fact, if a set of backup lightpaths
share a same link but their corresponding primary lightpaths
do not share common SRLGs, a single channel (wavelength)
can be reserved for all these paths. Details on the resources
sharing are given in [4,10].