  Programmable data planes recently emerged as a prominent innovation in
Software Defined Networking (SDN), by permitting support of stateful flow
processing functions over hardware network switches specifically designed for
network processing. Unlike early SDN solutions such as OpenFlow, modern
stateful data planes permit to keep (and dynamically update) local per-flow
states inside network switches, thus dramatically improving reactiveness of
network applications to state changes. Still, also in stateful data planes, the
control and update of non-local states is assumed to be completely delegated to
a centralized controller and thus accessed only at the price of extra delay.
  Our LOADER proposal aims at contrasting the apparent dichotomy between local
states and global states. We do so by introducing a new possibility: permit to
take localized (in-switch) decisions not only on local states but also on
replicated global states, thus providing support for network-wide applications
without incurring the drawbacks of classical approaches. To this purpose, i) we
provide high-level programming abstractions devised to define the states and
the update logic of a generic network-wide application, and ii) we detail the
underlying low level state management and replication mechanisms. We then show
LOADER's independence of the stateful data plane technology employed, by
implementing it over two distinct stateful data planes (P4 switches and OPP -
Open Packet Processor - switches), and by experimentally validating both
implementations in an emulated testbed using a simple distributed
Deny-of-Service (DoS) detection application.
