The LHCb Eventbuilder: Design, Implementation and Operational Experience

The LHCb event-builder is implemented using a large Gigabit Ethernet network using a push-protocol for a single stage read-out at a 1 MHz event injection rate. The destination assignment and dynamic load-balancing are facilitated by LHCb's Timing and Fast Control system. The assembly of event 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, the protocol used and the performance during first data taking. The emphasis will be on the experience we gained during the running of such a large event-building network. We will discuss the problems we encountered and how we overcame them.