

For the Fall semester 2003, the schedule of the monthly meetings and invited presentations at OpNeAR
lab. is the following (Please check again for updates):





Presentation Abstracts 

Friday, September 5, 2003  4:00 pm  room ECSN 2.110
R&D activities at the Department of Telecommunications of BUTE
Speaker: Zsolt Pandi
The presentation will introduce the past and ongoing research and
development activities of the Department of Telecommunications of Budapest
University of Technology and Economics (BUTE).
The workgroups of the Department focus on a number of different
research topics, such as modeling, design and analysis of
telecommunications networks, modeling, measurement and analysis of network
traffic, and other related problems. The presentation will
give an overview of the various international and national
projects related to the research activities of the Department.


MultiFailure Survivability in Optical Networks
Speaker:Parthasarathy Kothandaraman
This talk presents a novel protection strategy that copes with
network multiple consecutive and unrelated failures in the presence of
dynamic traffic. The strategy is based on the rerouting of orphan
endtoend connections upon occurrence of the (first) failure.


Friday, October 3, 2003  4:00 pm  room ECSN 2.110
The Disjoint PathPair Matrix Approach for Online
Routing in Reliable WDM Networks
Speaker: Paolo Monti
In reliable Wavelength Division Multiplexed (WDM) networks the
optimal choice of Routing and Wavelength Assignment (RWA) for the
working and protection pathpair is often a complex problem to solve.
To cope with such problem complexity, the Disjoint PathPair Matrix
(DPM) approach has been introduced and studied. With the DPM approach
the RWA problem complexity can be significantly reduced by limiting the
number of candidate pathpairs considered in the optimization.
Simulation results are collected using the DPM approach to solve the
online RWA problem in a network based on the Shared Path Protection
switching scheme with Differentiated Reliability. When compared to
the conventional kshortest paths approach, the DPM approach
requires up to one order of magnitude less candidate pathpairs. In
addition, the DPM approach finds solutions with reduced hop length of
both the working and protection paths by up to 3% and 14%, respectively.


Performance evaluation of
wavelength/waveband routed network using semilightpath algorithm
Speaker: Ramesh Kumar Manickam
The capacity of a Wavelength Division Multiplexing (WDM)
network can be improved by a selective upgrade of the optical
processing capabilities of its wavelength/waveband routing nodes. In
the case of wavelength routing, the focus is on optimal placement of
wavelength converters and on optimal tuning of wavelength changing
facility. The investigation has been carried out in a wavelength
converting network with regular mesh and ring topologies under static
and dynamic traffic scenario. An efficient criterion is proposed to
trade off between the blocking rate and the number of nodes that allow
wavelength conversion and their percentage of wavelength conversion
facility. The network average link usage is monitored to ensure proper
utilization of the network resources, to validate the optimization
design and to draw conclusions about the network scalability.
The advantage of hybrid OXCs which involve both all optical (OOO) and
electrical(OEO) switching lies in the reduction of swtiching cost by
aggregating wavelength paths into waveband paths and switching them
through the transparent optical layer. Simulation studies have been
carried out in a joint wavelength and waveband routed networks to
select the wavelength convergence point(WCP) and the wavelength
divergence point(WDP) nodes on the call blocking probability for a
given static traffic.


Friday, October 17, 2003  4:00 pm  room ECSN 2.110
Blocking in WavelengthRouting Networks
Speaker: Divanilson R. Campelo
Wavelength routing networks resemble previous
circuitswitching networks, as the lightpath established between two
nodes may be considered as a circuit between them. Although there has
been recently much interest in other ways of switching in alloptical
networks (ex.: packet and burst switching), circuit (or lightpath)
switching is still the most promising approach today for optical
networks. Among the performance metrics for such networks, blocking
has been the most important one in its design. Then, given the
existence of previous theory on circuitswitching blocking networks,
there was a natural will to reuse its results on the blocking
performance of alloptical networks, focusing on the their
peculiarities: the wavelength continuity constraint when nodal
conversion capabilities are not available; and the relatively poor
connectivity of the first optical networks. Most of former discussions
were based on the Lee approximation, which is particularly inaccurate
when nodal degrees are small, as in current optical networks.
The objective of this talk is to discuss some results of
existing theory of blocking in wavelength routing networks and to
present new models of blocking that have been investigated by our
group recently. We propose a better substitute for the independent
link assumption present in the classical Lee approximation. The
classical independent link assumption recognizes the existence of only
two kinds of objects in the network: single free (available) links,
which do support requests for new paths; and single busy
links, which donot support them. In real networks, however,
independent single busy links may occur only in 1link paths. Any path
with H > 1 links will give rise to a set of H spatially connected busy
links. The new assumption then takes all active paths, as well as all
free links, as independent objects on the network topology. The new
model is shown to generate a very good fit with the blocking
probabilities obtained through simulations on linear topologies using
Poissonian, spatially homogeneous traffic. We also discuss the
independent wavelength assumption in our analysis. Some results of our
theory will be published this year in SPIE Opticomm 2003 and IEEE
Globecom 2003.


Friday, November 7, 2003  4:00 pm  room ECSN 2.110
Performance versus Cost Analysis of WDM Networks
Speaker: Sonal D. Sheth
The objective of the presentation is to compare three wellknown WDM
network architectures (firstgeneration, singlehop, and multihop)
when they are deployed to accommodate dynamic endtoend connections
that require subwavelength transmission rates. The comparison is
based on a performance figure that is uniquely defined to take into
account the various architecture costs  determined by the cost of
the deployed network elements. The defined performance figure permits
also to compare the three architectures for all possible linetonode
cost ratio values.


Differentiated Reliability in Optical Networks  Experimental and
Simulations Results
Speaker: Dhruvish Shah
The Differentiated Reliability concept is developed by a in OPNEAR lab
with Centralized Connection Management. The concept is extended to be
applied to Distributed Connection Management. The initial part of the
study focuses on Optical Mesh Network for Emerging Gigabit Application
(OMEGA) Test bed findings.
In order to compare the concept with pure Shared Path Protection scheme
for larger topology, Network Simulator is used. Connection blocking in
19 node network is analyzed. When resource reservation for a connection
fails, either due to lack of resources in the network or due to
contention of a resource as a result of distributed control; it is not
dropped from the network. The connection is reattempted until it is
successful. Effects of reattempt strategy in case of First Fit (FF) and
Random Fit (RF) of routing and wavelength assignment (RWA) are studied.
A connection will be dropped from the network only when the source node
server is busy serving a previous connection.


Friday, December 5, 2003  4:00 pm  room ECSN 2.110
Distributed Local Recovery from Multiple Link Failures in MPLSTE Networks
Speakers: Kai Wu, Priti Mahale, and Sudheer Vinukonda
Highly timesensitive network applications require fast recovery
not only from failure of single network element but also from
simultaneous failures of multiple network elements. Current local
recovery schemes in MPLS TE networks achieve 10s of ms recovery
time under the assumption of single network failure. This paper is
aimed to extend the applicability of MPLS local recovery to
multiple failure scenarios. The proposed approach classifies
multiple failure scenarios into different risk levels based on the
fact that each scenario features different failure probability.
Multiple failure scenarios increase substantially the difficulty
both in finding the bypass tunnels around the failure and in
identifying the failure scenario. Two approaches, faultdependent
approach and faultindependent approach are proposed by taking the risk
level information into consideration during both bypass tunnel
computation and selection. These two approaches trade recovery
time with recovery ratio.
 
