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Slow file transfers over DS3

I have a bridged unchannelized DS3 running to a separate facility out of state. I'm running IRB on both edge routers to bridge the connection. Whenever we do a file transfer it seems to be taking much longer that what you would expect for a DS3. Right now there is no traffic on it and it takes 10 min. to transfer 1GB of data. I started looking into common problems experienced by high-bandwidth high-delay type networks. Theoretically increasing my TCP window size  and turning on window scaling on my test boxes should have increased file transfer speeds, but it did not seem to help at all even though I can see the increased window in an Ethereal dump. Anyone have any ideas?
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flisom
Asked:
flisom
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1 Solution
 
OAC TechnologyProfessional NerdsCommented:
how fast are the network cards in the computers you're transfering files to and from?
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flisomAuthor Commented:
Both are GB cards connected at 100MB to the switch.
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r_naren22atyahooCommented:
100Mbps will transfer
100*60 =6000Mbits per 1 Min
i.e 750MB per 1 Min
8GB will be transfered in 10.66 Min

regards
Naren
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r_naren22atyahooCommented:
100*60 =6000Mbits per 1 Min
bits to Byts=divide by 8
6000/8 = 750

regards
naren
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flisomAuthor Commented:
Let me explain, my PC has 100MB connection to my local switch. The PC I'm transferring to is in another state. The transfer goes from my local switch to our edge router. The edge router has a DS3 (45Mbit). The router is also switching local traffic. The PC I'm transferring to also has a 100MB connection to it's local switch.  My router config looks good, but what I'm questioning is if we have a high-bandwidth, high-delay condition on our network. Based on the DS3 alone I should be able to see at least 360MB a min, but I'm only seeing around 100. I've used the Iperf utility, in which I've used a TCP window of 90K and can transmit a file that's 1.1GB across in about 4 min. but when I actually set me TCP options in XP I see an increased window, but it's still just as sluggish.
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giltjrCommented:
Is there any other traffic on the DS3?
What is the utiliziation of the DS3 while doing the transfer?
What MTU is being used?
What FTP server are you using?
I am assuming you are using XP built in ftp client, try using the command:

     ftp -w:65000

then do the file transfer.  Have you got a packet tracing tool?  If not, I would suggest using something like Ethereal (http://www.ethereal.com) and looking to see what it may show.
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quistlogicCommented:
is the other connection site doing the same thing you are?  work together on this one.  it is possible they are being bogged down by something else.  

if worse comes to worse and you've exausted your resources, try talking to your provider.  they may have some insite in to your problem.
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skaap2kCommented:
Other things to consider :-

where you are downloading from, and what latency is there, latency can have a dramatic effect on throughput as the ACK's only arrive much later before the server starts transmitting data.

rgds,
Rob
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flisomAuthor Commented:
Thanks for the comments guys. We're not actually using FTP at all for file transfers. I'm testing with a simple cut and paste in Windows right now, but the bulk of the file transfers will be between 2 AIX machines performing some kind of remote copy function. There is not any other data going across right now as we're testing it. Whenever we do a transfer (from either location) however large, there is not much of a load on the routers or the NICs of the sending/receiving PCs. When I use tools like Iperf to measure bandwidth and test window scaling there is a load and it seems to act as it should. We've spoke at length with BellSouth and have had both local loops as well as the long haul tested extensively with no errors. We're not doing any kind of Internet downloading, this is just a simple inter-network file transfer. The ping latency is an average of 16ms. I found the formula for setting the TCP window and 45Mbit * 16ms = around 90K which isn't too far off from the Windows max of 65 so that might not be the problem. I've enabled TCP window scaling on both machines and although it will use a larger window for some transfers I'm not seeing any kind of significant performance enhancement. Anyone know of any other file transfer utilities or tools like Iperf I can use to test this link?
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giltjrCommented:
What happens if you attempt to send 2, 3, or even 4 files using FTP from the Windows box at the same time?
If it takes 10 minutes to send all of the files at the same time, then the performance issue is with the Windows ftp client.

If it takes 10xN (where N is the number of transfers you are attempting to do at one time) then try sending files from 2, 3, or 4 different Windows PC's at the same time.  If it takes 10 minutes for each PC to send its file, then the problem is with Windows IP stack.  

If it takes 10xN, then I would say there is either an issue with the T3 or with the FTP server.

What is the underlying connection on the T3: ATM, Frame Relay, or something else?
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flisomAuthor Commented:
The T3 is bridged so the only IP stack it's seeing is from machine to machine. There are no other IP encapsulation points along the way. I'm using default Cisco HDLC encapsulation. This link is more of a long back-to-back link. The more files I push across whether by FTP or any other means the more loaded the link becomes and more NIC utilization I see, but the transfer time remains the same. It takes each PC 10 min to transfer the 1GB of data, but conversely it takes the server 10 min to send the same file to the PC. A T3 should be able to send a 1GB file in about 3 min. and we're not seeing near that.
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giltjrCommented:
If I understand what you are saying that is:

     1 PC sending a 1GB file takes 10 minutes

     3 PC's each sending 1GB  file concurrently takes 10 minutes

It this is true, then the problem does not seem to T3, but maybe with either Window's having a single connection that can push large amounts of data over a WAN link, or problems with Windows ftp client pusing large amounts of data over a WAN link.

With one PC sending a 1GB file in 10 minutes you are getting about 100 MBpm, which is about 1/3 of what  T3 should be able to do.  With 3 PC's each sending a 1GB file in 10 minutes at the same time, you are getting 300 MBpm, or just under the capacity of a T3.

Is the sending and receive hosts on the same IP subnet?  I don't know this for a fact, but it would seem to me that a bridged network would see some type of delays that a routed network would not because of waiting for things at the Ethernet layer.

What do you have the HDLC frame size set to?

As you are using Windows I would assume that you have a file server on one side of the link. What happens if you copy a file using the copy command (or cut/paste from the gui)?
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flisomAuthor Commented:
I'm concerned with the fact that it's bridged as well. I'm not sure what latency that might put on the link other than encapsulation delay maybe? The HDLC MTU defaults to 4470 which I might try scaling to see if we get any changes. I've been testing with the copy/paste function of Windows which is where I get 100MBpm. I have tested FTP and TFTP transfers, but we will not be using FTP at all in this network so I haven't been relying on it for my tests (the transfer times for FTP and TFTP have also been way above 100MBpm anyway). I have also tried the CLI copy in Windows with the same results.
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giltjrCommented:
O.K. So the 100MBps is from the Windows copy and paste?  That's fine, unless the AIX copy will be based on SAMBA/NetBIOS.

SAMBA/NetBIOS is a chatty, chatty, did I say chatty, protocol.  Heck I'm supprised that you got 100MBpm.

Just to show you, I did a copy of a file that is about 700MB from my laptop (100Mbps to a file server (gigabit).   My laptop and the server are on the same switch.  Guess what, I got about 120MBpm, yep on a LAN where the slowest connection point is 100 Mbps,  I got just barely over what you are getting on a WAN that is only 45 Mbps.

Use the numbers you are getting for the FTP process, not Windows SAMBA/NetBIOS copy.

You may want to find out exactly what the AIX people are going to be using to do the file transfer.  They could be using RCP, SCP, cp to a NFS mount, or cp to a SAMBA mount.  If they say cp to a SAMBA mount, start crying now.  Anything else should work fine.
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flisomAuthor Commented:
Thanks. I think that this rate may just be what we're stuck with for now. No we're not running SAMBA on the boxes, which I'm really grateful for! Thanks again giltjr, since you helped with your test I'm awarding you the points. Have a good day!
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