  In 5G networks, slicing allows partitioning of network resources to meet
stringent end-to-end service requirements across multiple network segments,
from access to transport. These requirements are shaping technical evolution in
each of these segments. In particular, the transport segment is currently
evolving in the direction of the so-called elastic optical networks (EONs), a
new generation of optical networks supporting a flexible optical-spectrum grid
and novel elastic transponder capabilities. In this paper, we focus on the
reliability of 5G transport-network slices in EON. Specifically, we consider
the problem of slicing 5G transport networks, i.e., establishing virtual
networks on 5G transport, while providing dedicated protection. As dedicated
protection requires large amount of backup resources, our proposed solution
incorporates two techniques to reduce backup resources: (i) bandwidth
squeezing, i.e., providing a reduced protection bandwidth with respect to the
original request; and (ii) survivable multi-path provisioning. We leverage the
capability of EONs to fine tune spectrum allocation and adapt modulation format
and Forward Error Correction (FEC) for allocating rightsize spectrum resources
to network slices. Our numerical evaluation over realistic case-study network
topologies quantifies the spectrum savings achieved by employing EON over
traditional fixed-grid optical networks, and provides new insights on the
impact of bandwidth squeezing and multi-path provisioning on spectrum
utilization.
