zdmb05@hou.amoco.com (David M. Burns) (06/29/91)
I have a question about possible TCP/IP throughput rates that can be expected through a satellite link. This problem has plagued us for awhile and we currently think we are running up against a possible protocol limitation. The problem: slow FTP transfer rates between two ethernet LANs connected via a T1 satellite link. "Slow" means on the order of 30-35 Kbytes/sec (though rates as high as 100 KB/s are observed when the connection first starts.) These are "large" datasets, 100Mbytes or better. The serial connection for the satellite has ciscos at each end. Much effort has been expended verifying cisco settings, satellite tuning, etc. The hosts involved are primarily SS-2s, though we have also tested tp other systems. People have tried adjusting buffer, window sizes and implementing the algorithms proposed in RFCs 1072 and 1185. Nothing seems to work. Tests have also been done using the ttcp program (to eliminate the INETD overhead, etc.) Even with ttcp, response across the link is abysmal. My particular group has been on the periphery of this, so some of the above is hearsay. (I can vouch for the intensive effort lots of people have given it, though...but we are still relatively new to tcp/ip and this one seems to have us stumped.) I can understand that when going ethernet -> T1, the router will probably become flooded and have to toss packets. Does anyone have a suggestion for minimizing this ? Where should we double-check, to be sure we haven't overlooked anything ? We don't expect 160 KB/s, but would sure like to improve our current situation. Any and all suggestions are welcome. Please reply via email, and I'll post a summary if warranted. Thanks in advance, David Burns dmburns@hou.amoco.com -- David Burns reply to: dmburns@hou.amoco.com Amoco Corp. ISD SSS/Mini-Micro Systems Houston, Tx. 713/556-7013