  In the future ALICE heavy ion experiment at CERN's Large Hadron Collider
input data rates of up to 25 GB/s have to be handled by the High Level Trigger
(HLT) system, which has to scale them down to at most 1.25 GB/s before being
written to permanent storage. The HLT system that is being designed to cope
with these data rates consists of a large PC cluster, up to the order of a 1000
nodes, connected by a fast network. For the software that will run on these
nodes a flexible data transport and distribution software framework has been
developed. This framework consists of a set of separate components, that can be
connected via a common interface, allowing to construct different
configurations for the HLT, that are even changeable at runtime. To ensure a
fault-tolerant operation of the HLT, the framework includes a basic fail-over
mechanism that will be further expanded in the future, utilizing the runtime
reconnection feature of the framework's component interface. First performance
tests show very promising results for the software, indicating that it can
achieve an event rate for the data transport sufficiently high to satisfy
ALICE's requirements.
