FTP upload issue

Unanswered Question
Oct 4th, 2008

hi, i have problem in upload to FTP server. i have two site with 2 Mb DXX circuit. The FTP server is behind one of my router. when i upload file it give 70Kb upload and 230 Kb download.

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Giuseppe Larosa Sat, 10/04/2008 - 03:19

Hello Waseem,

the TCP goodput is influenced by the TCP window settings.

With the original TCP window size a 16bit number representing octets=bytes a maximum of 65535 bytes can be moved before waiting for ACK coming from the other side.

So not only the available bandwidth but also the one way delay or RTT plays a role here.

To improve performance you can try to configure the TCP/IP stack on both end devices to use an extended TCP window

defined in RFC 1323

and selective acks

RFC 2018

For example we had servers people complaining of poor performance over 622 Mbps link and we discovered their servers werent using the extended TCP window.

Be aware that ftp programs measure performances in bytes/second and not bps= bit per seconds so sometime a mismatch is seen simply for this reason an 8 factor scale.

Hope to help


itdsmartnet Sat, 10/04/2008 - 04:01

Thanks for your early reply , tell me how to configure TCP/IP stack on both sites,

itdsmartnet Sat, 10/04/2008 - 09:32

thanks for your reply, i want to know that if the problem is with the TCP/IP windowing size why i can download at 230Kbps from the same server and cannot upload more than 88 Kbps.

Giuseppe Larosa Sat, 10/04/2008 - 10:47

Hello Waseem,

I could have misunderstood your question in first post.

I'm not sure but it may be the client uses a normal TCP window size in upload and the server uses a TCP extended window in sending.

I think this could happen.

the 2Mbps CDN is symmetric so you would expect the same performance but: the FTP server and the FTP client are different machines with different performance and settings.

I would try in this way:

on the FTP client open two FTP connections to the FTP server.

On both FTP sessions make two concurrent uploads what is the result ?

88 kbps or near double ?

in second case the limit is on the host TCP window size and tuning and the network is not limiting

If the overall goodput of two concurrent FTP uploads is still 88 kbps the network should be investigated for possible bottlenecks:

- errors on the switch port where the host is attached to

- any form of shaping or rate-limiting applied on traffic received on the router port on the site where is the FTP client

Hope to help


itdsmartnet Sat, 10/04/2008 - 10:58

hi Giuseppe

i have tried using concurrent uploads but the overall output is still 88kbps and there is not Qos implemented. i attach the host directly to router's fastethernet interface but the problem remains the same. The problem is with the uploading not with the downloading.


Giuseppe Larosa Sun, 10/05/2008 - 11:50

Hello Waseem,

what operating system is on FTP client ?

If it is any form of MS windows ,

have you got access to a linux box on the site ?

I would suggest to try with a linux box to perform FTP upload and see the results.

what are the error counters on the fast interface ?

are they steady or are they incrementing ?

Another method you could use if you have a pair of linux boxes one on each site is netperf:



I used it some years ago under FreeBSD.

In the long term if the upload speed of 88 kbps is not enough for your requirements you could think to deploy a WAAS system that have been introduced for these scenarios

They are able to speed up transfer.

the Cisco product in this category is :


hint: you could use this argument to take time with management if you are under pressure.

Hope to help



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