[TelstraClear] ftp upload speeds - can't get over 33 kBs

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lchiu7

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#23942 11-Jul-2008 15:43

I occasionally run a ftp server (Serve-U) so that a friend in the US can download some content I have created (well videos I have recorded of local shows).

He has never been able to get more than about 33-35Kb/sec on a download which is strange given we are supposed to have at least 2Mbs upload on the TCL cable. Even more interestingly, when he starts up multiple ftp sessions, he can have up to 5-6 sessions running, each at about 30Kbs eventually saturating the upstream link capacity so he can get the file reasonably quickly.

I also encounter a similar problem when using smartftp to upload files to a web server - I have never been able to get more than about 35Kbs upload speed.

Just wondering what the problem is. And this is with a number of different routers though I haven't yet tried plugging the PC directly into the modem.

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BarTender

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#147018 12-Jul-2008 07:51

Sounds like TCL are rateshaping FTP Upload Traffic. Either you could move the FTP to another port (depending on how smart their Layer 7 router is, it may pick up the change) or use a http or put ssl (https) on a server and see if that works any better.

Unless TCL have rate shaped all TCP traffic to limit each stream to 34KB/s... which could also be the case.

Otherwise you could try Filezilla see if that works any better.

Belsamber

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#147044 12-Jul-2008 10:31

I would expect the issue is more likely due to limitations imposed by TCP window size.

Most likely latency to the states is ~300ms, and if you (or your friend) are running XP (maybe, maybe not...?) then your default max TCP window size is 17520B.

17520B / 0.3s = ~58kB/s

(http://en.wikipedia.org/wiki/TCP_tuning)

Bear in mind that is the absolute max (including various overheads) you can get on a single TCP connection in perfect conditions, so 33kB sounds close enough.

Solutions: you can tune your TCP window (Google is your friend) or your friend could use a download manager which opens multiple TCP streams (most do.)

lchiu7

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#147156 12-Jul-2008 15:30

Belsamber: I would expect the issue is more likely due to limitations imposed by TCP window size.

Most likely latency to the states is ~300ms, and if you (or your friend) are running XP (maybe, maybe not...?) then your default max TCP window size is 17520B.

17520B / 0.3s = ~58kB/s

(http://en.wikipedia.org/wiki/TCP_tuning)

Bear in mind that is the absolute max (including various overheads) you can get on a single TCP connection in perfect conditions, so 33kB sounds close enough.

Solutions: you can tune your TCP window (Google is your friend) or your friend could use a download manager which opens multiple TCP streams (most do.)

No - the TCPWindowsize on the server running the ftp server was changed a while ago and is 256960 as is the Maxsegmentsize.

And he does run multiple ftp sessions to get the bandwidth up but I was wondering why the limitation. Also if I want to upload files to my web server I can't run multiple uploads so I am limited to the 33Kbs which is pretty annoying. Out of interest going to try http instead to see if it's TCL doing bandwidth shaping

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michaeln

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#147157 12-Jul-2008 15:50

Sounds like a TCP window size to me, and the fact that parallising the download lets you get to maximum bandwidth is a very strong argument in favour of that conclusion.

By the way, you you mean 33kbps or 33kBps (264kbps)?

Can you tell us what the ping time between you and your friend is? If you are both running Windows XP, than RWIN is by default 16kB (16384B). For the West Coast, a normal ping time would be about 150ms, which would lead to a maximum transfer rate of about 109kBps (874kbps). The East Coast is about 250ms away, or 65kBps max. (At the moment, UCB is 150ms and MIT is 250ms away from me).

Of course, other things could be putting your latency up, such as a slow ADSL link on the other end, hence the interest in your ping times.

michaeln

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#147178 12-Jul-2008 17:16

lchiu7:No - the TCPWindowsize on the server running the ftp server was changed a while ago and is 256960 as is the Maxsegmentsize.

And he does run multiple ftp sessions to get the bandwidth up but I was wondering why the limitation. Also if I want to upload files to my web server I can't run multiple uploads so I am limited to the 33Kbs which is pretty annoying. Out of interest going to try http instead to see if it's TCL doing bandwidth shaping

You changing your windowsize is not enough. He has to change his. It is the windowsize of the thing doing the receiving that matters in this case. That's also the problem with uploading to the server. The server is misconfigured, and there is little you can do about that.

To the very best of my knowledge, TCL is not doing FTP bandwidth shaping.

techo

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#147391 13-Jul-2008 12:58

lchiu7: the TCPWindowsize on the server running the ftp server was changed a while ago and is 256960 as is the Maxsegmentsize.

Actually, MaxSegmentsize (MSS) is a different parameter to Receive Window Size (RWIN).

MSS = MTU - IP_header - TCP_header (nominally MSS=1460B for 1500B MTU)

RWIN is the parameter you need to set, and also RFC1323 TCP_Window_Scaling must be supported & enabled on the TCP/IP stacks at both ends otherwise you will be limited to 64KB RWIN.

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lchiu7

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#147424 13-Jul-2008 15:37

We tried again today and each ftp session was running at about 40kBs tops. So with multiple sessions we got about 196kBs which is okay but a bit annoying. Also tried http - can't run multiple sessions that I am aware of and we maxed out at abouit 50kBs

Tried pinging him but destination can't be reached so perhaps I have a firewall or router issue blocking ICMP traffic

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michaeln

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#147441 13-Jul-2008 16:00

lchiu7:
Tried pinging him but destination can't be reached so perhaps I have a firewall or router issue blocking ICMP traffic

What about trying traceroute / tracert (Windows)? You might be able to get an idea at least of the next to last round trip time if nothing else.

Is your friend West Coast/Central/East Coast?

JonC

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#147599 13-Jul-2008 22:25

Try this web-site http://www.speedguide.net:8080 to see what your TCP/IP settings are and if they're optimised. I get good FTP upload speeds (up to about 100kBps) from my TCL cable account to Europe with these settings:

« SpeedGuide.net TCP Analyzer Results »
Tested on: 07.13.2008 06:21
IP address: x.x.x.x

TCP options string: xxxx
MSS: 1460
MTU: 1500
TCP Window: 513920 (multiple of MSS)
RWIN Scaling: 3
Unscaled RWIN : 64240
Reccomended RWINs: 64240, 128480, 256960, 513920
BDP limit (200ms): 20557kbps (2570KBytes/s)
BDP limit (500ms): 8223kbps (1028KBytes/s)
MTU Discovery: ON
TTL: 39
Timestamps: OFF
SACKs: ON
IP ToS: 00000000 (0)

Note that you need to make sure that if you're using a router that your MTU is set correcty on your PC as well as the router.

EDIT: also you don't need to encrypt - I've tried both, although I do use non-standard FTP ports. I don't think TCL are doing any shaping.

techo

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#147727 14-Jul-2008 13:21

Talking of routers, some routers do not support RFC1323 TCP_Window_Scaling when using NAT. This mainly applies to older routers or low-end routers. If you have a router(s) performing NAT, you should check that the router(s) support this, otherwise you will be limited to 64KB RWIN.

Works for Vodafone NZ. Any opinions expressed on Geekzone are my own, and not of my employer.