  Internal routing inside an ISP network is the foundation for lots of services
that generate revenue from the ISP's customers. A fine-grained control of paths
taken by network traffic once it enters the ISP's network is therefore a
crucial means to achieve a top-quality offer and, equally important, to enforce
SLAs. Many widespread network technologies and approaches (most notably, MPLS)
offer limited (e.g., with RSVP-TE), tricky (e.g., with OSPF metrics), or no
control on internal routing paths. On the other hand, recent advances in the
research community are a good starting point to address this shortcoming, but
miss elements that would enable their applicability in an ISP's network.
  We extend pathlet routing by introducing a new control plane for internal
routing that has the following qualities: it is designed to operate in the
internal network of an ISP; it enables fine-grained management of network paths
with suitable configuration primitives; it is scalable because routing changes
are only propagated to the network portion that is affected by the changes; it
supports independent configuration of specific network portions without the
need to know the configuration of the whole network; it is robust thanks to the
adoption of multipath routing; it supports the enforcement of QoS levels; it is
independent of the specific data plane used in the ISP's network; it can be
incrementally deployed and it can nicely coexist with other control planes.
Besides formally introducing the algorithms and messages of our control plane,
we propose an experimental validation in the simulation framework OMNeT++ that
we use to assess the effectiveness and scalability of our approach.
