The explanation lies in transiting circuits with high latencies and/or packet loss, whether they're the last mile by dial up or frame circuit backbone connections. Larger packets are more prone to be corrupted or discarded so sessions with smaller packets have a better performance in comparison. No excess retransmission and all that. We've seen it in networks where the customer connection is high quality but there were provider latency/loss problems. Smaller MTU helped while the frame relay problems persisted. Once the provider network was up to snuff there was no discernable performance difference between large or small and I think most of our users went back to defaults. > The improved-performance-with-low-MTU is a puzzle I'd certainly like to > understand better. It seems step 1 is to eliminate the possibility that > the 1500 MTU is leading to fragmentation.
Vern
Doug Stanfield Oceanic Cable Data Networking Manager 200 Akamainui St. dougs@oceanic.com Mililani, HI 96789