  Operators of reconfigurable wavelength-division multiplexed (WDM) optical
networks adapt the lightpath topology to balance load and reduce transmission
delays. Such an adaption generally depends on a known or estimated traffic
matrix. Network function virtualization (NFV) allows to implicitly change this
traffic matrix. However, these two degrees of freedom have largely been
considered separately, using resources suboptimally. Especially for
delay-sensitive services, an optimal use of resources can be crucial.
  We aim to jointly optimize the embedding of virtualized network function
(VNF) forwarding graphs with delay constraints and the lightpath topology of
WDM optical networks. Unlike previous work, we consider all three types of
delays: propagation, processing and forwarding-induced queuing delay. We model
the latter two as M/M/1 queues.
  We formulate and analyze a mixed-integer nonlinear program (MINLP),
reformulate it as a mixed-integer quadratic constrained program (MIQCP) and
approximate it by a mixed-integer linear program (MILP). We evaluate our
approach for small-scale examples of a multicast service.
