  In communication networks, network virtualization can usually provide better
capacity utilization and quality of service (QoS) than what can be achieved
otherwise. However, conventional resource allocation for virtualized networks
would still follow a fixed pattern based on the predicted capacity needs of the
users, even though, in reality, the actual traffic demand of a user will always
tend to fluctuate. The mismatch between the fixed capacity allocation and the
actual fluctuating traffic would lead to degradation of provisioned network
services and inefficiency in the assigned network capacity. To overcome this,
we propose a new spectrum trading (ST) scheme between virtual optical networks
(VONs) in the context of an elastic optical network (EON). The key idea here is
to allow different VONs to trade their spectrum resources according to the
actual capacity they need at different time instants. A VON with unused spectra
can then trade away its unused spectra to other VONs that are short of spectrum
resources at that time. In exchange, it is rewarded with a certain amount of
credit for its contribution to the ST community, which it can then use later to
get extra bandwidth, if needed. The trust-worthiness of the trading records
between the VONs is ensured in a distributed fashion through a
blockchain-assisted account book that is updated whenever a new trade occurs.
For this, we develop a software-defined control plane to enable spectrum
trading in an EON. The performance of the ST scheme is evaluated and compared
with a scenario without such trading. Our results show that the proposed ST
scheme is effective in improving the QoS of each VON and significantly improves
the overall network capacity utilization.
