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researResearch
problem as being a variant of the knapsack
problem. This modelling led to two publications
one of which in the prestigious IEEE
Communications Letters. We highlighted several
possibilities for future research into stabilizing
approximation algorithms on those subjects.
Access networks and metropolitan
optic networks
Minh Thanh Ngo has almost completed his PhD
on upstream traffic management in EPON
(Ethernet Passive Optical Networks). The three
components of a control plane for EPON have
been identified:
1. a Dynamic Bandwidth Assignment (DBA)
implemented at network head (in the Optical Line
Termination, OLT) and which is coupled to
scheduling policies implemented at the users’
gateways (in Optical Network Units, ONU);
2. a method for controlling the conformance of
upstream traffic to traffic profiles negotiated in
the Service Level Agreement;
3. a Call Acceptance Control (CAC) also
implemented at network head.
A simple and versatile traffic management policy
was proposed regarding points 1 and 2. Several
publications have shown its efficiency. These
results have been mostly obtained by simulation
using Network Simulator (ns-2). However, using
the similarity between upstream traffic
management in EPONs and polling systems, we
have also been able to derive some analytical
results relative to mean waiting times in EPONs
with heterogeneous traffic.
As for optic packets in metropolitan networks, we
participated in the conception of an MAC for such
networks, in the context of the ANR ECOFRAME
project. We also obtained first results concerning
the impact of user behavior on networks
dimensioning; we showed that the increase in
peer to peer traffic within the metropolitan
network would allow a better utilization of
resources.
We also undertook collaborations with Pisa
University within the framework of the BONE
Network of Excellence, and with PRISM
(University of Versailles) within ECOFRAME, in
both cases on the theme of metropolitan optical
packet rings dimensioning.
Engineering of SIP services
This study consists of setting up "policies" for
selection of "optimal" network exit links in
private networks. The criteria used are the
quality of the connection, its cost or the type of
SLA.
A rules server has to be designed which will
interface with « Session Border Controller »
(SBC) which in turn interfaces with private
networks through the different available exit
points.
Sajjad Ali Mushtaq began a PhD thesis on this
topic; initial studies consisted of identifying
relations between terminals. One system
incorporating a softswitch, a SBC, an edge router
and a policy server has been proposed and
published. We also identified how the use of a
specific message header on SIP messages
allowed the softswitch and the SBC to implicitly
share the decision to accept a new call.
A model of this system is under development. A
first version uses an ASTERISK softswitch and a
version of SBC supplied by our partner Converse.
This model should evolve in 2009 to use the
softswitch supplied by Alcatel-Lucent.
Publications
Thesis
Dimitri Marakov. Contributions to the traffic matrix problem. Th. doct:
Informatique: Institut Télécom; Télécom Bretagne,
Université de Rennes 1 : 2008, 2007telb0058. 179 p.
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