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FTP upload is disrupted

asked 2021-03-06 18:50:45 +0000

Hi I am having a recurring problem when I upload a file from the maintenance server (CENTER) to a branch server The upload is suddenly interrupted half way through the file transfer

Other that a lot of retransmissions, I don't see something wrong in the pcap files

The wireshark captures, on both sides, where made connecting a windows host to a mirror port on the local switches The communications between the sites are thru a site to site VPN

Here are the captures!AhaIf1uNR2GF8V1ua...

Thanks, in advance

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answered 2021-03-09 19:06:18 +0000

André gravatar image

updated 2021-03-09 19:09:00 +0000

It is not wrong, but SACK, Selective Acknowledgement, is not enabled on So when packet loss occurs the file transfer stalls in your case and TCP slow start is triggered again.

Enable SACK when possible.

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Thank you I am going to tray to enable it.

lwbuyer gravatar imagelwbuyer ( 2021-03-10 02:45:59 +0000 )edit

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Asked: 2021-03-06 18:50:45 +0000

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Last updated: Mar 09 '21