The LHCb eventbuilder: Design, implementation and operational experience

The LHCb event-builder is implemented using a large Gigabit Ethernet network using a very lean push-protocol for a single stage read-out at 1 MHz event injection rate. Destination assignment and dynamic load-balancing are facilitated by LHCb's Timing and Fast Control system. Assembly of fragments is done on each event-filter farm node instead of having dedicated builder units. The design of the event-builder will be shortly described, followed by a description of the implementation, protocol and performance results. Emphasis will be on experience in running such a large event-building network and the problems which we encountered and how we overcame them.