Verification of High Data Rate Bandwidth-on-Demand networks: User Based Test Equipment

TrackTrack 1 (Auditorium 1)
DescriptionElectronic Very Long Baseline Interferometry (eVLBI) uses high data rate academic networks to send data from radio telescopes to a central processing centre. The networks have the capacity to provide 10Gbps connections, but the applications often only need such high data rates intermittently. The NEXPReS project (, in collaboration with network providers and GÉANT, aims at providing a Bandwidth-on-Demand (BoD) service for eVLBI in Europe. Such connectivity needs to be verified before observations using real-time data transfers can begin. User Datagram Protocol (UDP) is the best format for eVLBI data however dedicated links are required to avoid denial of service to others, hence BoD offers an ideal solution.
We compare the use of two different hardware solutions for the measurement of network characteristics, a Field Programmable Gate Array (FPGA) based bespoke solution and a general purpose PC. The PC ran the UDPmon software, a network test and diagnosis tool specifically designed for UDP, and the FPGA was designed to send and receive time-stamped UDP packets in a compatible manner.
We find that both systems perform well, producing data rates of over 9.9Gbps on an 80km 10GE static test link. The FPGA system has considerably smaller jitter in inter-packet arrival time, but the PC is easier to programme and can be used for other purposes. We will report on our initial experience of using BoD paths requested from the AutoBAHN system over several different paths with end hosts in the UK, Sweden and Finland. We will also present the performance of the PC systems for verification of the inter-administrative domain BoD circuits at rates of up to 4Gbps, and what these represent in terms of future international BoD links for eVLBI and other data intensive experiments.

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