High data rates employed in transparent optical networks (TONs) demand reliable transmission between node pairs
realized through different protection and restoration schemes. Besides component faults causing node or link failures,
services may also be disrupted by certain malicious attacks which target the vulnerabilities of TON physical-layer
components, such as high-powered jamming. The consequences of such attacks can differ significantly from component
faults, so classical techniques used for protection may not necessarily guarantee survivability against them. To provide
attack-aware protection in TONs, we develop a dedicated path protection algorithm in which we identify the so-called
attack groups of each primary and backup path and perform RWA in a way which ensures that they are attack groupdisjoint.
Wavelength division multiplexing (WDM) technology is considered to be the ultimate answer to the rapidly growing
capacity demand of next generation networks. Many routing and wavelength assignment (RWA) algorithms, proposed
for lightpath provisioning, base their routing decisions on the availability of network resources, and assume that optical
fibers and components are ideal. In reality, physical impairments degrade the quality of the optical signal propagating
through fiber segments and optical components. To cope with this problem, Impairment Constraint Based Routing
(ICBR) algorithms, that consider physical impairments during connection provisioning, are currently proposed to prevent
selecting lightpaths with poor signal quality. However, these algorithms support only a single (highest) quality of
transmission threshold, the same one for all connection requests. This does not fit well with the variety of services, with
potentially disparate QoS requirements, that the next generation networks are expected to support. Consequently, the
efficiency of network resource utilization is reduced.
This paper demonstrates that a significant improvement, in terms of blocking probability, can be achieved when using an
ICBR algorithm with differentiated physical layer constraints. Performance is compared with conventional impairment
aware routing approaches when unprotected, shared path protected (SPP), and dedicated path protected (DPP)
connection requests are considered. The achieved improvement is a result of more efficient resource utilization as
unnecessary connection blocking can be avoided by selecting network resources offering optical signal quality that is
"good enough" to satisfy a specific connection request.
In transparent Wavelength Division Multiplexing (WDM) networks, the signal is transported from source to destination
in the optical domain through all-optical channels, or lightpaths. A lightpath may traverse several fiber segments and
optical components that in general degrade the optical signal. This effect introduces the need for considering physical
layer impairments during the connection-provisioning phase. Physical layer impairments can be divided into linear and
non-linear. Both types of impairments are highly dependent on the fiber characteristics, which in turn are sensitive to
length, temperature and age. A close look at the fiber infrastructure of today's network operators reveals a situation
where old and newly deployed fibers coexist in the network. This heterogeneous fiber plant presents a challenge. A
tradeoff should be found between the QoS requirements of connection requests and the use of the available (old and
new) network resources. This calls for a provisioning mechanism able to adapt to the various fiber composition
In parallel, given the need for service differentiation, the authors recently proposed an Impairment Constraint Based
Routing (ICBR) algorithm, referred to as ICBR-Diff, supporting differentiation of services at the BER (Bit Error Rate)
level in a network with a homogeneous fiber infrastructure. In this paper the ICBR-Diff algorithm is extended to
heterogeneous network; particularly, it is evaluated in WDM networks with fiber links having varying Polarization Mode
Dispersion characteristics, i.e., with old and new fiber coexisting. Simulation results show that the ICBR-Diff algorithm
exhibits high adaptability in a heterogeneous fiber composition scenario. This translates into improved performance in
terms of blocking probability, when compared to traditional impairment aware routing algorithms.
An optical packet switch based on wavelength routing and optical waveband conversion is demonstrated. The switch performs header extraction, packet routing, and regeneration and exhibits very good physical performance.
Although recent advancements in WDM technology have significantly enhanced the performance and reliability of optical components and systems it remains inevitable that failures occur. Due to the massive
increase of bandwidth supported by fiber networks it becomes extremely important to identify the impact individual failures may have on the network performance. This paper focuses on understanding the different parameters that affect the reliability of optical networks with emphasis on failures caused due to the optical components comprising the network infrastructure. As part of this study the reliability parameter associated with individual optical components is associated with the reliability of a link. Through extensive simulations it is shown that there is a direct impact on the traffic distribution across the network depending on the reliability characteristics of the network infrastructure. Several reliability scenarios and their relevant results will be presented, discussed and compared. The different scenarios under study are based on a national USA network topology and include both protection and no protection routing.
Conference Committee Involvement (2)
Network Architectures, Management, and Applications
13 November 2011 | Shanghai, China
Network Architectures, Management, and Applications VI