Photon Netw Commun (2008) 16:233–238
New trafﬁc grooming approaches in optical networks under restricted
P. P. Sahu
Received: 29 January 2008 / Accepted: 27 May 2008 / Published online: 27 June 2008
© Springer Science+Business Media, LLC 2008
Abstract In this paper, two trafﬁc grooming approaches
based on alternate path routing are proposed to accommo-
date a greater number of connections in optical networks.
In the ﬁrst approach (called as Source_SWG), the connec-
tions of same source and different destinations along a path
are groomed in a wavelength channel, whereas in the second
approach (called as Des_SWG), the connections of the same
destination and different sources along a path are groomed
in a wavelength channel. These approaches are compared
with existing heuristic trafﬁc grooming algorithms based on
ﬁxed routing. It is found that both the approaches provide
less wavelengths than the existing heuristic trafﬁc grooming
algorithms for establishment of all the connections present
in the network. The comparative studies of these approaches
are also made under restricted shared protection. It is seen
that in case of Source_SWG, the number of wavelengths
required for establishment of all the connections present in
the network is less than that for Des_SWG.
Keywords Shared protection · Setup time · Blocking
probability · Trafﬁc grooming
Recently, WDM networks with trafﬁc grooming have been
focused due to its efﬁcient utilization of network resources.
Most of the connections such as voice, data, and text in
the network require a small amount of bandwidth. Without
grooming, these connections would occupy a full-dedicated
wavelength. However, the network does not have enough
P. P. S ahu (
Department of Electronics and Communication Engineering,
Tezpur University, Tezpur 784028, Assam, India
wavelengths to support each connection with a dedicated
wavelength. In this regard, trafﬁc grooming is a technique,
which aggregates multiple low-speed trafﬁc steams into a sin-
gle wavelength. The fundamental problem of trafﬁc groom-
ing in WDM networks is how to route and assign wavelengths
and groom the trafﬁc connections to minimize the number
of wavelengths per link in the network, i.e., the number of
Add/Drop multiplexer (ADM) as well as the number of trans-
ceivers in the network. Most of the previous work on trafﬁc
grooming has used a special topology, such as ring topology
[1–4]. Very few works of trafﬁc grooming [5–7] have been
made on a general topology optical network.
The failure of a trafﬁc groomed path in the network leads
to loss of many connections, which are groomed on the same
path. So backup path provisioning  is essential for pro-
tection of these connections against failures. The failures are
of two types: link and node failures. Link failures may be
due to ﬁber cuts, transceiver failures, etc. It requires other
routes for the affected link. When node failures occur due to
a transceiver problem, a back up path, which is not passed
via the failed nodes, is used. In this paper, we focus on only
handling of link failures, which might occur more frequently
than node failures.
The paper is organized as follows. Section 2 presents
the relevant backgrounds of trafﬁc grooming and protection
mechanism. Section 3 presents the details of the proposed
approaches and problem formulation. The performance anal-
ysis of the proposed techniques is mentioned in Sect. 4.
Section 5 concludes the paper.
2 Previous work
This section presents relevant background work on trafﬁc
grooming in WDM mesh networks under shared protection.