Post on 27-Jan-2021
Abstract—Wavelength converters help to reduce the blocking probability of the network and enhance the fibre utilization. Since
wavelength converter is an expensive component with respect to
other components in optical network researches are constrained in
minimizing this cost keeping the blocking performance as optimum
as we can. The impact of the proposed algorithms on blocking
probability is investigated. These algorithms are compared on the
basis of blocking probability; number of channels and number of
links are kept constant whereas the response of the algorithms is
calculated by varying the load per link (in Erlangs). The blocking
probability is also calculated for the network with wavelength
conversion and without wavelength conversion.
Keywords— Wave division multiplexing, Wavelength Converters, Blocking performance.
I. INTRODUCTION A. Traffic grooming
RAFFIC grooming is the process of grouping many small
telecommunications flows into larger units, which can be
processed as single entities. For example, in a network using
both time-division multiplexing (TDM) and wavelength-
division multiplexing (WDM), two flows which are destined
for a common node can be placed on the same wavelength,
allowing them to be dropped by a single optical add-drop
multiplexer. Often the objective of grooming is minimizing the
cost of the network. The cost of line terminating equipment
(LTE) (also called add/drop multiplexers or ADMs) is the
most dominant component in an optical WDM network's cost.
Thus grooming typically involves minimizing the usage of
ADMs. [1]
The transmission capacity of a link in today’s optical
networks has increased significantly due to wavelength
division multiplexing (WDM) technology. The network
performance is now mainly limited by the processing
capability of the network elements, which are mainly
electronic. By efficiently grooming low-speed traffic streams
onto high-capacity optical channels, it is possible to minimize
this electronic processing and eventually increase the network
performance. Traffic grooming is an emerging topic that has
been gaining more research and commercial attention.
Most previous research on traffic grooming is mainly based
Neeraj Mohan is working as HOD in Deptt. Of Computer Science & Engg.
Rayat & Bahra Institute of Engineering & Bio-Technology, Sahauran, Distt.
Mohali (Punjab)-140104 INDIA
Amanjot Kaur is student in Computer Science & Engineering
Department, Rayat & Bahra Institute of Engineering & Bio-Technology,
Sahauran, Distt. Mohali (Punjab)-140104 INDIA.
on the ring network topology. It is expected that there will be
much more interest on the mesh topology suitable for
longhaul, wide-area networks. This paper reviews most of the
recent research work on traffic grooming in WDM ring and
mesh networks.
Data streams within a single optical fiber are carried over
different wavelengths. Each wavelength can be further divided
into more than one channel having a lower ratio of the entire
wavelength bandwidth. A lightpath from a source to
destination may be formed using such wavelength channels of
finer granularities. Efficient planning for placing the grooming
devices within a mesh network is a complex task. Placing the
grooming devices all over the mesh network can be both cost
significant and lead to a bad performance. [2]
Traffic grooming in wavelength division multiplexing
(WDM) optical networks routes and consolidates sub-
wavelength connections onto lightpaths, to improve network
utilization and reduce cost. It can be classified into static or
dynamic, depending on whether the connections are given in
advance or randomly arrive/depart.[3]
The concepts of blocking probability, and end-to-end
blocking probability, which are used interchangeably, are
equivalent to the so-called burst/packet loss ratio defined as a
ratio of the bursts/packets that are lost to the bursts/packets
that are sent. The main cause of loss is lack of sufficient
network resources as losses due to physical layer errors are
negligible.
Traffic grooming refers to the problem of efficiently
packing low-speed connections onto high-capacity lightpaths
to better utilize network resources.[4]
II. LITERATURE SURVEY Hongyue Zhu et.al. [5] had proposed a new generic graph
model for traffic grooming in heterogeneous WDM mesh
networks. The novelty of this model was that, by only
manipulating the edges of the auxiliary graph created by model
and the weights of these edges, model can achieve various
objectives using different grooming policies, while taking into
account various constraints such as transceivers, wavelengths,
wavelength- conversion capabilities, and grooming
capabilities. Based on the auxiliary graph, we develop an
integrated grooming algorithm, IGABAG, which jointly solves
the four traffic-grooming subproblems for one traffic demand,
and a grooming procedure, INGPROC, which can
accommodate both static and dynamic traffic grooming using
the IGABAG algorithm.
Srivatsan Balasubramanian et.al. [6] provide an overview
Dynamic Traffic Grooming in Optical Networks
Amanjot Kaur, and Neeraj Mohan
T
2nd International Conference on Emerging Trends in Computer and Electronics Engineering (ICETCEE'2013) Sept 17-18, 2013 Hong Kong
31
http://en.wikipedia.org/wiki/Telecommunicationshttp://en.wikipedia.org/wiki/Telecommunications_networkhttp://en.wikipedia.org/wiki/Time-division_multiplexinghttp://en.wikipedia.org/wiki/Wavelength-division_multiplexinghttp://en.wikipedia.org/wiki/Wavelength-division_multiplexinghttp://en.wikipedia.org/wiki/Optical_add-drop_multiplexerhttp://en.wikipedia.org/wiki/Optical_add-drop_multiplexer
of the optical and electronic grooming techniques available
with focus on IP as the client layer .They studied networks of
various connectivities to identify scenarios where light-trails
can compete with e-grooming lightpath networks.
Xin Wan et.al. [7] have introduced a dynamic traffic
grooming approach in bandwidth-flexible multi-layer
IP/optical networks. A novel IP/optical multi-layer routing and
grooming algorithm is proposed to calculate the routes for
bitrate -flexible IP traffic over spectrum-flexible optical
networks. The algorithm employs a bandwidth threshold, an
auxiliary graph, and two grooming policies. Numerical results
show that the dynamic grooming approach achieves lower
blocking probabilities compared with IP-over-WDM and non-
grooming flexible networks. They have proposed a novel
dynamic traffic grooming approach in flexible multilayer
IP/optical networks, which support IP/MPLS traffic demands
with flexible bitrates.
Shuqiang Zhang et.al. [8] have studied dynamic traffic
grooming in elastic optical networks. He has proposed an
auxiliary graph to implement several traffic-grooming policies
.There results show that there is a tradeoff among different
traffic-grooming policies and they should be adopted
according to the network operators objectives and network
circumstances. Spectrum elastic optical networks support
flexible central frequency and spectrum assignment for
lightpaths. When provisioning a new connection in an elastic
optical network that allows traffic grooming, the control plane
has to solve two problems: the electrical-layer routing and
optical-layer routing and spectrum assignment (RSA). The
electrical-layer routing determines how to route the new
connection through a combination of new and existing
lightpaths , while the optical-layer RSA decides how to
establish new lightpaths under the spectrum continuity
constraint.
Wang Yao et.al. [9] have studied dynamic traffic grooming
in WDM mesh optical networks using fixed-alternate routing.
They proposed the FOG grooming algorithm which supports
on-line provisioning of multi-granularity sub-wavelength
connections. Based on the two-layered routing characteristic of
the traffic grooming problem, they introduced the route
selection problem (or grooming node selection problem) on
the candidate paths. To address the route selection problem,
they proposed three grooming policies which include load
sharing (LS), sequential grooming (SG) and minimum gap
(MG). They proposed three other grooming policies, least
physical hop first (LPH), least virtual hop first (LVH) and
least stringent resource first (LSR), to address the wavelength
and transceiver constraints in grooming networks
Mr. Anurag Anant Mishra et.al. [10] have examined
blocking probability computational model, for calculating the
probability in optical burst switched network due to
insufficient transmission calls blocked by network congestion
during the busy hours. Their main focus was that packets /data
are found at the destination or not and retransmits the packets
/data which is not transmitted during the busy hours of network
congestion in a timely manner to avoid traffic in the network.
Farouk E. El-Khamy et.al. [11] have studied the blocking
performance with wavelength converters depends on many
factors such as network topology, number of wavelengths
available, and traffic patterns. For short paths there is no
significant change in the blocking performance in case of full
conversion case than that of no-conversion case but for long
paths there is a large enhancement especially for the large
traffic load.
Shilpi Garg et.al. [12] have studied the Routing and
Wavelength Assignment (RWA) problem in wavelength-
routed optical WDM networks supporting dynamic traffic
arrivals. The problem of routing was studied using Dijkstra's
shortest path algorithm, with weight functions that utilized
WDM network characteristics.
Mahesh Sivakumar et.al. [13] have studied the blocking
performance of limited grooming networks. He had
investigated four different scenarios based on the port-sharing
architecture and constraints on the number of wavelengths
used by a connection, and proposed policies for grooming.
They considered the effect of several important factors
including: connection granularity, traffic grooming policy,
number of grooming ports per node, grooming port tunabilily,
and wavelength conversion. Simulation results indicate that
limited grooming at each node is sufficient to obtain the
performance obtained with full grooming, especially when
connections occupy a small fraction of the wavelength
capacity. Further, the connection granularity, the grooming
policy and the number of wavelengths used per link for a
connection are also seen to have a significant effect on the
performance
J.Q. Hu et.al. [14] have studied a sufficient condition under
which we proved that the decomposition method in fact
produces an optimal solution for the GRWA problem. In most
previous studies on optical mesh networks, traffic demands
were usually assumed to be wavelength demands, in which
case no traffic grooming is needed. In practice, optical
networks were typically required to carry a large number of
lower rate (sub-wavelength) traffic demands. Hence, the issue
of traffic grooming becomes very important since it can
significantly impact the overall network cost. In their study,
they consider traffic grooming in combination with traffic
routing and wavelength assignment. There objective was to
minimize the total number of transponders required in the
network. They proposed a decomposition method that divides
the GRWA problem into two smaller problems: the traffic
grooming and routing problem and the wavelength assignment
problem, which can then be solved much more efficiently.
Eytan Modiano et.al. [15] Traffic grooming is an effective
mechanism for providing optical bypass in WDM-based
networks to save electronic processing cost. The recent
emergence of WDM technology has led to a tremendous
increase in the available transmission capacity in wide area
networks. These networks may no longer be limited by
transmission bandwidth, but rather by the processing capability
2nd International Conference on Emerging Trends in Computer and Electronics Engineering (ICETCEE'2013) Sept 17-18, 2013 Hong Kong
32
of electronic switches, routers, and multiplexers in the
network. This realization has led to a new wave of research
aimed at overcoming the electronic bottleneck by providing
optical bypass at the WDM layer Traffic grooming can be used
as a bypass mechanism by which low-rate circuits are assigned
to wavelengths in order to minimize the amount of electronic
multiplexing equipment.
Yongli Zhao et.al. [16] have proposed an analytical
methodology for computing blocking probabilities for OFDM-
based bandwidth-variable optical networks with wavelength
continuity constraint. Numeric results that our proposed
analytical model, i.e WDA is close to the simulation results
with the blocking probabilities obtained through simulations
for call traffic loading. Compared with the rigid and coarse
granularity of Wavelength Division Multiplexing (WDM)
networks, Orthogonal Frequency Division Multiplexing
(OFDM)-based band width variable optical networks have the
advantages of good spectral efficiency, flexibility, and
tolerance to impairments, and can support the service with the
bandwidth requirement of higher or lower than one
wavelength. Blocking probability is one of the most important
parameters for circuit-based optical networks performance
evaluation, and of significance for the network planning.
Keyao Zhu et.al. [17] study was devoted to the traffic-
grooming problem in a WDM mesh network. They studied the
architecture of a node with grooming capability. They
compared the performance of the single-hop grooming
approach and multihop grooming approach on a small six-
node network with randomly generated traffic pattern. Results
from ILP showed that the end-to-end aggregate traffic between
the same node pair tends to be groomed on to the same
lightpath channel, which directly joins the end points, if the
optimization objective is to maximize the network throughput.
Two heuristic approaches were also proposed for solving the
traffic-grooming problem in large networks. They compared
the performance of these two heuristic algorithms, MST and
MRU, with different network resource parameters. The
comparison results showed that MRU performs better if
tunable transceivers are used and MST performs better if fixed
transceivers are used.
Canhui (Sam) Ou et.al.[18] they investigated the survivable
traffic grooming problem for optical mesh networks employing
wavelength-division multiplexing (WDM). Based on a generic
grooming-node architecture, we explored three approaches—
PAL level, MPAC level, and SPAC level—for grooming a
connection request with shared protection against single-fiber
failures.
III. CONCLUSION Traffic grooming has become an important issue in optical
networks. Blocking probability is an important parameter for
the traffic grooming. A network can be groomed to utilize its
maximum capacity. In this paper we have studied various
traffic grooming techniques and blocking probability of optical
networks
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http://en.wikipedia.org/wiki/Traffic_groomingmailto:cxin@nsu.edu