A detailed experimental performance evaluation on TCP over UBR

The ATM service category UBR is intended for non-real-time applications tha t do not require guaranteed QoS commitments. With additional, relatively in expensive control functions such as packet discard schemes, UBR could becom e a cost-effective alternative for the transmission of data traffic, offeri ng a straightforward and flexible solution as opposed to nrt-VBR and GFR th at applies stricter traffic specifications as well as ABR with its sophisti cated and complex rate-control protocol. This paper presents the results ob tained from a comprehensive set of experiments with TCP over UBR, comprisin g measurements taken on different protocol layers. The goal is to experimen tally investigate the performance of UBR to carry TCP traffic, to evaluate the performance gain achievable by packet discard schemes and TCP parameter tuning, to study the influence of the TCP implementation, and in a final s tep, to relate the measurements to simulation results.