Our discrete-system simulator (DSS) is used by INTRACOM, the largest Greek telecom company. We shall expand DSS (in connection with the DSP library) to allow for the specification, simulation and performance testing of distributed protocols for almost any form of environment, including networks that allow hierarchical description, very fast networks and heterogeneous networks with mobile units. The visualisation facility of DSS will be enhanced so the user can see the protocol execution in very large networks in a meaningful way through, e.g., a hierarchical description and graph-drawing techniques. INTRACOM, and also INTRASOFT (the largest Greek software company), are interested in the new DSS and DSP library for (1) simulating and testing distributed banking applications, and (2) designing hardware for fast networks (routers and switches).
During
the first year of ALCOM - IT, we established strong interactions with the
industrial link INTRAKOM/INTRASOFT a major Telecom and Systems House conglomerate
of Companies. After analysing the users' needs, we identified a large algorithmic
area which is a subset of the area of on-line algorithms, namely the area
of Call Admission Control (CAC) algorithms. Our group and, in general,
the ALCOM team has had already shown significant research on the issue.
Since the problem of Admission Control is currently addressing ATM network
technology, we decided to explore the transfer of algorithmic engineering
technology in that area by specializing and focusing the ALCOM-IT produced
DSS tool in the above direction. The new DSS tool aims to provide:
The ATM technology is considered as the state of the art network technology
that is expected to play an important role in the future networks. The
ATM networks are fast packet switching networks achieving their speed by
avoiding flow control and error checking at the intermediate nodes in a
transmission. ATM operates in a connected mode, but a connection can only
be set up and serviced if sufficient resources are available in order to
preserve the quality of service to the previous accepted connections. This
function is controlled by the Call Admission Control algorithms running
in the ATM switches.
DSS provides an abstract model for the description of any ATM network which
is independent of details of the underlying technology. It simulates the
basic functionality of an ATM network which IS that in each time unit cells
are produced from traffic generators or forwarded from the switches to
their destination.
Under the scope of DSS an ATM network topology consists of links, ATM switches,
terminals (workstation) and call/traffic generators (network applications).
The critical characteristics of the topology such as the size of the buffers
of the ATM switch, the bandwidth of the links, the virtual paths and virtual
circuits over the links and the traffic parameters can be defined by the
user to approach the behaviour of the today's and the future network components.
Each ATM switch is modelled as a Communicating Finite State Machine. A
receipt of a CAC cell combined with its current state activates an action
routine of the CAC algorithm.
Emphasis is given in the abstract modelling of traffic generation. Adversarial
traffic leads the on-line algorithms to their worst case competitive ratio
of performance (measured against ideal off-line algorithms that know the
future). The DSS cannot simulate worst-case adversaries but can approximate
their behaviour by exploiting certain distribution of call request of high
Kolmogorov complexity. The DSS can of course use externally (pragmatic)
generated call sequences.