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

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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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[4] K. Zhu and B. Mukherjee, “A review of traffic grooming in WDM optical networks: Architectures and challenges,” SPIE Opt. Networks

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http://en.wikipedia.org/wiki/Traffic_groomingmailto:cxin@nsu.edu