time structure analysis of the lhcb daq network

Gianni Antichi (1) , Marc Bruyère (2) , Daniel Campora Perez (3) , Guoming Liu (3) , Niko Neufeld (3) , Philippe Owezarski (2) , Andrew W Moore (1) , Stefano Giordano (4)

1 Computer Laboratory [Cambridge]
2 LAAS-SARA - Équipe Services et Architectures pour Réseaux Avancés
3 CERN - European Organization for Nuclear Research
4 Dipartimento di Ingegneria dell'Informazione [Pisa]

The LHCb DAQ Network is a real time high performance network, in which 350 data sources send data over a Gigabit Ethernet LAN to more than 1500 receiving nodes. The aggregated throughput of the application, called Event Building, is more than 60 Gbps. The protocol employed by LHCb makes the sending nodes transmit simultaneously portions of events to one receiving node at a time, which is selected using a credit-token scheme. The resulting traffic is very bursty and sensitive to irregularities in the temporal distribution of packet-bursts to the same destination or region of the network. In order to study the relevant properties of such a dataflow, a non-disruptive monitoring setup based on a networking capable FPGA (Netfpga) has been deployed. The Netfpga allows order of hundred nano-second precise time-stamping of packets. We study in detail the timing structure of the Event Building communication, and we identify potential effects of micro-bursts like buffer packet drops or jitter.

Mots clés: NetfPGA; latency; measurement; CERN; LHCb

Domaines: Réseaux et télécommunications [cs.NI]

Gianni Antichi, Marc Bruyère, Daniel Campora Perez, Guoming Liu, Niko Neufeld, et al.. time structure analysis of the lhcb daq network. Computing in High Energy and Nuclear Physics (CHEP), Oct 2013, Amsterdam, Netherlands. ⟨hal-00908383⟩