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Long sized files and TCP problems

Hi, I've got a problem with transfer of long sized (80 - 100 GB) files via FTP between two Unix servers. Two servers are on different sites and LAN connections to local routers (one is 2610 and the other is 3640) are fastethernet. Connection between two sites is provided by 2 X 2Mbps MLPPP link. FTP transfer is taking really long time (app. 10 hrs.) and generally at a moment during the transfer FTP session is breaking and starting over. I've heard someting about that TCP CRC mechanism doesn't work well for this kind of very long connections. Despite serial lines of the multilink interface are not noisy should I consider to use another link layer protocol (eg. LAPB) that can handle error correction better? If so how can I bundle these links like the way MLPPP does?


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Re: Long sized files and TCP problems

I beleive the figures in the data you provided are inaccurate. Basically you say that you can transfer a 100GB file over a 4Mbps link in 10 hours. According to my calculations, the absolute minimum this can take is 55 hours. This assumes no link/protocol overhead and no other IP traffic on the link.

100GB = 800Gb = 800,000Mb

800,000Mb / 4Mbps = 200,000 sec = ~55 hours


Re: Long sized files and TCP problems

Excuse, I've provided the data from the sys admins; 10 GB of data in 12-13 hrs.

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