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As part of a subproject on IP congestion
control, we studied the benefits of Explicit Congestion
Notification (ECN) and Backward Explicit Congestion Notification
(BECN) on a test bed with different TCP modifications. Both ECN
and BECN showed considerable improvements over traditional
methods of congestion control in IP networks. The evaluation of
BECN showed further improvement over ECN. Furthermore, we studied
different active buffer management schemes for Assured Forwarding
Per Hop Behavior (AF-PHB) in a differentiated services (DiffServ)
environment. Important results related to buffer management
schemes for AF PHB have been derived and published.
The work already performed has shown positive results in favor of
explicit congestion control (ECN and BECN). Further study for
improvement is being done with BECN and Multi-Level BECN
initially using the ns simulator. The project was recently
completed. The student Akujobi has completed his masters thesis
and is now employed by Carleton University (Department of
Computing and Communication Services). The research is in the
area of comparison of BECN and ECN and optimal adjustment of the
BECN control parameters for minimizing congestion in IP routers.
A paper was published in IEEE Globecom 2002. Furthermore, the
student Yi has extended similar results for congestion control in
gateways, completed his masters thesis and submitted a research
publication in October 2003. The student Adegboyega is also
working in this area and he is expected to complete his thesis in
early January 2004.
Turning to the project on video multicasting over IP, we modeled
and developed a software realization of an MPEG4 video traffic
generator (which was contributed to the ns community and can be
found at
http://www.isi.edu/nsnam/ns/ns-contributed.html) using the
Transform Expand Sample (TES) methodology. The implementation was
done in C++ and OTcl and was integrated in the network simulator
ns. We investigated problems with multi-rate (layered) approaches
for video multicast congestion control. We identified the source
of unfair behavior of a layered approach to congestion control
for video multicasting. We showed the effect of three factors on
fairness: the flow/congestion control used by the video transport
protocols for multicast applications, the traffic rate
distribution across the video layers and third, the burstiness of
the video source. ECN for video multicasting was developed based
on RED buffer management. This research was motivated by and is
connected with the first part of the project on IP congestion
control. We proposed the use of different forms of explicit
congestion notification (ECN, BECN and MECN) to avoid congestion
while it is being developed in a network. Some of these
techniques have already been in use in the case of unicast
traffic (in the first part of our project). We proposed its
extension to the multicast case. We have done a performance study
of end-to-end architectures using network support from different
ECN techniques for the multicasting of MPEG4 over IP.
The student Matrawy has further elaborated in the areas of
explicit congestion notification and performance study of
end-to-end architectures using Diffserv based QoS for video
multicasting. A number of publications have been accepted to
referred IEEE journals. He successfully defended his doctoral
thesis and awarded the degree in the summer 2003 convocation.
Regarding the sub-project in the area of optical networks
performance the research has developed in two main areas. We have
studied the extension of the Border Gateway routing Protocol (BGP)
to optical networks. The BGP has been used in the Internet for
interdomain routing. However, contrary to packet networks (such
as the Internet) optical networks need to open end-to-end
connections (lightpaths), since routing cannot be done on a
hop-by-hop manner (as in the Internet) if optical to electrical
conversion is not used (which is expensive, slow and therefore
not desirable). Modifying BGP in order to be used in optical
networks and operate by setting up lightpaths in an end-to-end
fashion is a major task. Simulations in OPNET enabled us to
propose the necessary modifications and transform BGP to Optical
BGP (OBGP). Furthermore, performance analysis of routing
protocols in optical networks has been initiated in collaboration
with researchers from the faculty of the School of Mathematics
and Statistics at Carleton University. One doctoral student,
co-supervised by Prof. Lambadaris and Prof. Zhao, has
investigated the performance of OBGP under different wavelength
availability/distribution schemes for establishing end-to-end
lightpaths. Numerical approximations and simulations using OPNET
are in close agreement.
In terms of student training The student Francisco has completed
his masters thesis on OBGP and is defending in January 2004. The
students Li and Pezoulas have successfully defended their masters
degree in the area of optical network routing. The student Zhang
has successfully defended his masters in the area of path
protection in optical networks.
Finally, the following extensions to the research are as follows:
For the sub-project in IP congestion control we are currently
investigating MPEG 4 video multicasting and related security
issues over MPLS networks. In the area of optical networks we are
investigating optimal wavelength allocation in WDM networks and
scheduling in optical resilient packet rings.
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