Resilience in Transparent Optical Networks
All-Optical Networks (AONs) are a relatively new technology for very high data
rate communications, flexible switching and broadband application support. More
specifically, they provide transparency features allowing routing and switching
of data without interpretation or regression of signals within the network. AONs
contain only transparent optical components and therefore differ to a large extent
from the optical networks currently used. In particular, the behaviours of AON
components and architectures bring forth a new set of challenges for network
security. As a result, AONs have unique features and requirements in terms of
security and Quality of Service (QoS) that require a highly targeted approach
in terms of network management.
Network management for AONs faces additional security challenges that arise
from AON components they employ. Whilst some of available management mechanisms
are applicable to different types of network architectures, many of them are
not adequate for AONs and must therefore be carefully addressed. In particular,
network transparency raises many security vulnerabilities that differ substantially
from conventional failures and should be therefore treated differently. One of
the serious problems related to transparency lies in the fact that optical
crosstalk is additive and can be exploited to perform service disruption attacks
upon the whole network. Since these attacks can spread rapidly through the network,
causing additional failures and triggering multiple alarms, they must be detected
and identified at any point in the network where they may occur. However, to monitor
all wavelength channels at several detection points in any node in the network is
likely to be a very expensive solution.
The presence of a Network Management System (NMS) is essential to ensure efficient,
secure, and continuous operation of any network. Specifically it handles the management
of configuration, fault, performance, accounting, and security aspects, which are usually interlinked to one other. A key component in this system is the performance management
as it provides signal quality measurements at very low bit error rates and fault diagnostic support for fault management. Performance management is still a major complication for AONs, particularly, because signal quality monitoring is too difficult in AONs as the analogue nature of optical signals means that miscellaneous transmission impairments aggregate and can impact the signal quality enough to reduce the QoS without precluding all network services. This results in the continuous monitoring and identification of the impairments becoming challenging in the event of transmission failures. However, a simple and reliable signal quality monitoring method does not exist at present. Despite new methods for detection and localization of attacks having been proposed, no robust standards or techniques exist to date for guaranteeing the QoS in AONs. Therefore, the need for expert diagnostic techniques and more sophisticated management mechanisms that assist managing and assessing the proper function of AON components is highly desirable.
