Photonic Network Communications, 3:4, 363±375, 2001
# 2001 Kluwer Academic Publishers. Manufactured in The Netherlands.
Optical Data Network Basedon the Switchless Concept:
University of Rome ``La Sapienza'', INFOCOM Department, Via Eudossiana, Rome, Italy
Davide Parisi, Roberto Sabella
Ericsson Lab Italy, Via Anagnina 203, 00040 Rome, Italy
ReceivedApril 23, 2001; RevisedJuly 6, 2001
Abstract. The ``switchless'' all-optical network aims to provide a future single-layer, advanced transport architecture on a national scale. The
single-hop, shared-access network employs time and wavelength agility (a WDMA/TDMA scheme), using fast tuneable transmitters and
receivers, to set up individual customer connections through a single wavelength router, which is suitably replicated for resilience. While in a
recent paper we reported the analysis and dimensioning of a switchless network assuming just the telephone traf®c, we provide in this paper a
new model, which contains innovative elements, and report original results assuming to deal with data traf®c of two different types: constant bit
rate (CBR) and variable bit rate (VBR). The innovation is based on the fact that the model considers more traf®c ¯ows with different traf®c
requirements (e.g., bandwidth, duration) as input to a group of time-slot connections on the same wavelength between two passive optical
networks (PONs). We obtainedanalytical expressions of the main traf®c characteristics (loss probability, throughput andover¯owing traf®c)
both for the primary group of time-slots andfor the secondary group of time-slots, to which the over¯owing traf®c streams enters.
Moreover, we show that the innovative network structure, i.e., use of a passive wavelength router node (PWRN), works also perfectly with
more different traf®c streams.
The analytical model presented in this paper has been compared with a simulation model. The comparison has revealed very good agreement.
Relevant network cases are considered, and the dimensioning of the network in such cases is reported, in terms of the key network parameters,
loss probability andthroughput.
Keywords: switchless network, passive wavelength router, wavelength agility
Besides telephony, a modern telecommunication
network must be able of providing a large number
of other services, such as ®le andimagine transfer,
videoconference, CATV and multimedia applications.
With the internet growing in importance, the transport
of these services experiencedtremendous growth, so
much so that in the future the penetration of these
services will be far higher than the telephony. In order
to reach this aim, a generic network must adapt itself
¯exibly anddynamically to the new scenario. In
particular, it must resolve new problems such as the
transport of different traf®c streams in the network
and appropriate handling of streams with different
characteristics and different needs [9,10].
In the present work, we want to upgrade the
``switchless'' network described in Binetti et al.  so
that it can provide different services in addition to
telephony. All these additional services will form a
traf®c stream that we will name data traf®c to
distinguish it from the classic telephone traf®c. In
particular, for this data traf®c we intend to consider
traf®c generatedby CBR (constant bit rate) andVBR
(variable bit rate) sources.
The aim of this work is to provide a new model,
which can be practically usedfor the dimensioning of
switchless networks, under the assumption of
transporting different traf®c streams, each one
characterizing a speci®c service. The necessity of a
new model is simply explained as follows.
The structure of the switchless network is reported
in Fig. 1 (for more details see Binetti et al.  and
ACTS-SONATA ). It performs the switching and
routing functions within a single network layer by
providing end-to-end optical connections among a