FTP behaviour

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groenie

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Hi all

I'm seeing some strange behaviour with FTP uploads and downloads. I regularly need to upload and download from a client's site that is connected to the IS network via 2x256 kbps dignet lines. The problem is that I get low transfer rates - typically 1-10kB/s. This is on both our 512 & 128 packages. What bothers me is the fluctuations in the transfer rate. I used windows performance monitor to graph it, and it fluctuates wildly between 0 and 17.

For comparison, I can do HTTP downloads at a steady 25-35 kB/s for hours using GetRight (eg. Project Entropia which is 550MB). I also used our company diginet connection to FTP to the client and then the transfer rate is very stable.

I see the fluctuating transfer rates mainly on sites connected to IS which really seems strange. I also see it when using BitTorrent and Direct Connect, but I don't know if that is normal.

My only theory is that it is because of dropped packets and retransmissions, but why would HTTP downloads be stable then?

I'm still using my Coffee cantenna and my signal is 18-24%, so maybe that is responsible for a fluctuating signal.

Groenie
 
Interesting question, I have 50% signal and I experience the exact same thing on FTP, especially when uploading.


<hr noshade size="1"><center><font color="blue">MyWireless Stuff</font id="blue">
<font size="1"><font color="black">The opinions expressed here are mine alone and do not necessarily reflect the opinions of my employer</font id="size1"></font id="black"></center>
 
I think when the Packets get dropped, the ftp server needs to confirm what is still being downloaded etc, in a thread and the IS server might take longer at doing that, I have noticed it on the Saix network as well.

Keep Surfing
 
Is there any way to tell if packets are begin dropped? I'm using the perfmon counters under RAS Port and Ras Total, but I've never seen any of the error counters being incremented.

BTW, the FTP server I connect to is a Windows 2000 Server running IIS. I wonder what ftp.is.co.za is? It just says Unix.

FTP uploads on the 128k package is virtually impossible. The connection gets broken every 100kB or so and I've never been able to upload more than 2MB successfully. I haven't tried to upload using the 512k package - will do that tonight.
 
i have the 512k, and uploaded 192mb to ftp.uunet.co.za succesfully without interuptions at a clean 25kb/s (sometimes dropping to 24.5kb/s)

I rule [8D] [:p]

Why do you have to "put your two cents in"... but it's only a "penny for your thoughts"? Where's that extra penny going to?
 
mmmm,

Me thinks it smells of the transparent proxies at IS again [8D]

I may be mistaken but http/ftp priorities are different on IS's MPLS network...

I'll ask around ;-)

R
 
Can the prioritizing of traffic or the bandwidth limiting that Sentech does cause packets to be dropped? I would expect these mechanisms to introduce an artificial delay, but not drop packets - is this true?

Groenie
 
It would not drop packets, the strange thing is that my signal is at 51% and packets are dropped still one in every 10 on average, on a normal ping to multiple sites. as ping is ICMP which I am sure will be at the lowest priority of the IS MPLS network in general. I think the server at IS and SAIX may be the problem. [:D]

Keep Surfing
 
Sup

Proasm, i've heard rumours that Sentech are changing their routing to got through saix not IS. True or not ? just interested to see what the gaming pings will be like if this happens. Tx

Dr4k out
 
noone, with your 512k download max.. have you managed to get more than 10KB/sec on IRC DCC downloads?

I am used to getting about 6-7K on ISDN but now with my 128k MyWi I cant seem to get more than 3 or 4K/sec with the occasional spike here and there.

I suspect port shaping.. so is there a way around it or any local IRC DCC servers on which we can test this?

For a DCC Fserve (assuming port shaping in place) is it the exact same process as a DCC send from say me to you? (for testing purposes if no local DCC Fserves around)
 
Might sound stupid, but I'm trying to understand this bandwidth limiting:

If I start to FTP upload, my modem sends data to the tower at 3Mbs which ends up on the PPP server where its buffered and then sent upstream at 128kbps, right? Now, the control message takes a much longer time to get to my FTP client than expected, so it decides to resend, again at 3Mbs. Story repeats, and gets worse exponentially.

I don't know if this can happen, but it does explain the behaviour I'm seeing, where the uploads starts OK, but goes slower and slower until grinding to a complete halt.

On downloading the same thing happens because the server is sending me data at 512kbps, also only to be limited by the Sentech server, which explains the erratic transfer rates.

This would obviously only happen if FTP experiences the bandwidth limiting differently from normal congestion.

Please tell me if I'm way off here! [:D]



Groenie
 
IS cap downloads from their FTP to 10KBps unless you are an IS customer.

Technicaly Sentech should be an IS customer [?]

Maybe if noone asks me nicely i can see if i can get the MyWireless block unlimited on ftp.is.co.za

- Colin Alston
colin at alston dot za dot org

"Warning: Use with extreme caution."
 
<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by groenie</i>
<br />Might sound stupid, but I'm trying to understand this bandwidth limiting:

If I start to FTP upload, my modem sends data to the tower at 3Mbs which ends up on the PPP server where its buffered and then sent upstream at 128kbps, right? Now, the control message takes a much longer time to get to my FTP client than expected, so it decides to resend, again at 3Mbs. Story repeats, and gets worse exponentially.

Please tell me if I'm way off here! [:D]
Groenie
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

You're on the right track.

The "control message" wont take that long to time out at 3MBps or whatever. TCP/IP is cleverer than that, as in it sends at 3MBps, which the tower drops, resends at half that, fails, resends at half untill it gets to 128K and then increases slowly untill it fails again and it halfs it etc. On your MyWireless connection this should be happening on OSI layer 2 or so, so you shouldnt be effected per connection, this should constantly be happening.

((For people interested - this poses a problem on large capcaity links and PVCs. Imagine your GIG-E bandwidth getting halved due to one error!))

The problem I see at home on FTP uploads is that its 100Mbps to my router and then like 128K out or whatever. With QoS rules in place I see it 'pulse', like upload a 128K chunk and then pause for a few seconds, then another etc.

- Colin Alston
colin at alston dot za dot org

"Warning: Use with extreme caution."
 
<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Karnaugh</i>
<br />IS cap downloads from their FTP to 10KBps unless you are an IS customer.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

I'm uploading to another company's FTP server who is a client of IS.
I think you guys are right, I'm a victim of port shaping.[V]
I don't mind port shaping so much, except if it completely breaks my FTP uploads, which are mission critical to me.


<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">The "control message" wont take that long to time out at 3MBps or whatever. TCP/IP is cleverer than that, as in it sends at 3MBps, which the tower drops, resends at half that, fails, resends at half untill it gets to 128K and then increases slowly untill it fails again and it halfs it etc. On your MyWireless connection this should be happening on OSI layer 2 or so, so you shouldnt be effected per connection, this should constantly be happening.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

Would it not be a solution if the tower/PPP server could let the modem know what the limit is? That would cut down on wasted bandwidth and dropped packets.

Groenie
 
Hey

I been downloading from my friends ftp (dsl) and i was getting 14kbs solid on my 256k [B)].

Dr4k
 
<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by groenie</i>
<br />I'm uploading to another company's FTP server who is a client of IS.
I think you guys are right, I'm a victim of port shaping.[V]
I don't mind port shaping so much, except if it completely breaks my FTP uploads, which are mission critical to me.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
IS do <b>NOT SHAPE TRAFFIC ARBRITRARILY AND NEITHER DO SENTECH</b>.
they <b>JUST</b> shape on <b>ftp.is.co.za</b>

(This is not a flame just a clarification)

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">Would it not be a solution if the tower/PPP server could let the modem know what the limit is? That would cut down on wasted bandwidth and dropped packets.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
Uh, no. It would still happen down the line, and everywhere, like I think I said. This is how the internet works, on your tower link this would happen once on the PPP tunnel if at all and then stabalise, it doesnt constantly flap.

- Colin Alston
colin at alston dot za dot org

"Warning: Use with extreme caution."
 
Just an update: I'm currently downloading ISO's using GetRight doing segmented downloads from FreeBSD sites all over the world and my combined speed &gt; 60 kB/s on 512k package. [:p]


Everything is via FTP. The one thing I can see is that FTP from IS is slow like Karnaugh said, so it seems Sentech is not an IS customer.

Now I just need a solution for uploading.

Groenie
 
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