The Ethernet spec. prohibits "significant" levels our out-of-order delivery, so out-of-order packets are not likely to be the problem within Reni's Ethernet LAN.
Most Ethernet switches drop internally when packets arrive faster than they can be sent and buffers overflow. (This is true even if hardware flow control is enabled on the links.) Reni's 100mbit links are trivially overwhelmed by a gbit sender. In such fast->slow cases, you should expect to see periodic retransmissions as part of TCP's normal congestion detection, which repeatedly ramps up the send rate linearly until a timeout occurs (because a packet was dropped) and then slows by a factor of 2 and retransmits all unacked packets. It would be normal to see <=75mbit/s throughput in the gbit->100mbit direction, even with no other traffic on the network. It would only be normal to see no retransmissions if the TCP send window was small enough to never overflow the buffering at the 1gbit->100mbit transition. It sounds to me like Reni's network has <16K buffering at the 1gbit->100mbit transition. --Glenn _______________________________________________ gPXE mailing list [email protected] http://etherboot.org/mailman/listinfo/gpxe
