topic Re: FTP transfer speed in Operating System - OpenVMS

FTP transfer speed

Vladimir Fabecic — Tue, 27 Mar 2007 01:59:18 GMT

Hello
Maybe that is stupid question, but must ask.
When doing ftp transfer between two nodes (in local LAN), I can get near 500 Mbps.
But when doing ftp between two locations, transfer rate can not be more than 72 Mbps.
There is gigabit ethernet connection between these two location.
I have tried with following parameters: TCPIP$FTP_WNDSIZ, WINDOW_SCALE and TCP QUOTA settings.
What else can be done?
Did I miss something?

Re: FTP transfer speed

labadie_1 — Tue, 27 Mar 2007 02:06:17 GMT

May be
$ set rms/network
and
$ set rms/extend=65535

?

Re: FTP transfer speed

Steven Schweda — Tue, 27 Mar 2007 02:17:44 GMT

Same versions of all the FTP client and
server programs? There have been some
speed-related fixes in TCPIP's FTP stuff in
the past year.

Re: FTP transfer speed

Vladimir Fabecic — Tue, 27 Mar 2007 02:30:31 GMT

Thanks for reply.
Labadie, will try with rms parameters.
Steven, it is HP TCPIP V5.5 - ECO 1 and OS version is 8.2 AXP on all VMS nodes.

Re: FTP transfer speed

Wim Van den Wyngaert — Tue, 27 Mar 2007 02:48:50 GMT

May be one of the routers on the way to the destination is in 100 Mbs ?
Had the problem in decnet with a 10 Mbs.

Wim

Re: FTP transfer speed

Vladimir Fabecic — Tue, 27 Mar 2007 03:29:50 GMT

Hello Wim
Network people say that everithing is OK with network switches and there are no packets lost.
And they also said that latency is 4-5 ms (miliseconds).

Re: FTP transfer speed

Hein van den Heuvel — Tue, 27 Mar 2007 05:55:34 GMT

speed of light limitation? how far are those sites apart?

the system can not just pump data and never look back.
There has to be an 'ack' at some point.
At that point you the delay becomes more important than the bandwidth.

Hein,

Re: FTP transfer speed

Robert Gezelter — Tue, 27 Mar 2007 06:10:02 GMT

Vladimir (and Gentlemen),

Changing parameters can be helpful, or it can have unintended side effects.

The first step is understanding the precise nature of the problem. I suggest using a LAN monitor to see if the problem is propagation delay. If this is indeed the problem, the problem can be tracked down.

In some cases, it is the inherent delay, in other cases it is the setup of the network. There can be surprises here. With ready availability of WireShark (formerly Ethereal) the tools are inexpensively available.

- Bob Gezelter, http://www.rlgsc.com

Re: FTP transfer speed

Wim Van den Wyngaert — Tue, 27 Mar 2007 06:19:35 GMT

Just to be sure : do a traceroute (mc tcpip$traceroute node) to see what route is followed. Then ask the network team if all are capable of Gigabit ethernet. Also ask if this is the correct route.

If the ethernet trace is too difficult : try
$ tcptrace/pack=1000/prot=tcp/port=21/fu/out=x.lis node
and post x.lis

Wim

Re: FTP transfer speed

Vladimir Fabecic — Tue, 27 Mar 2007 09:10:14 GMT

Did a traceroute before. Network guy said it is OK.
Hein, those sites are 400 km apart.
Of course there has to be an 'ack' at some point. The point is: how to optimize packet/acknowledge ratio. And maybe there is nothing to do on VMS to help. But maybe some parameter change can help.
Wim, will try to do tcptrace tomorow.
Thanks everybody for reply.

Re: FTP transfer speed

Wim Van den Wyngaert — Tue, 27 Mar 2007 09:33:29 GMT

You didn't specify your tcp version but on 7.3 with 5.3 I found that for every few thousands (or was it hundreds ?) of packets of data there is an ACK. Depends on the window size agreed between both parties (check in tcptrace : it's there).

Wim

Re: FTP transfer speed

Steven Schweda — Tue, 27 Mar 2007 09:45:10 GMT

> You didn't specify your tcp version [...]

Not soon enough, perhaps, but:

Mar 27, 2007 07:30:31 GMT
> it is HP TCPIP V5.5 - ECO 1 and OS version
> is 8.2 AXP on all VMS nodes.

Re: FTP transfer speed

Hoff — Tue, 27 Mar 2007 09:47:31 GMT

Just who is this mysterious Network Guy?

He seems to work everywhere.

When asking a question of Network Guy, you need to be very careful what question you ask, as you can get the answer to a question you didn't intend to have asked. Many incautious questions asked of Network Guy can seemingly be interpreted as "is the network down?", unfortunately.

Try asking Network Guy this question: "What is the wide area link between site X and site Y? SONET?" (And to avoid breaking the spell, SONET is usually pronounced as "sonnet".) Then, when and if prompted for more: "Which SONET level; which OC?"

It looks like you don't have gigabit between the sites, which isn't a huge surprise. Low-latency bandwidth is expensive, and the cost of low-latency bandwidth rises very quickly. (An example of a high-latency high-bandwidth link: the "FedEx network packet"; a FedEx truck chock-full of LTO or Ultrium cartridges, or of terabyte disks.)

It looks like you might have an OC-3 SONET connection between the sites.

To get gigabit-grade speed between sites, you'd likely need OC-18 or OC-24 -- and you might well have to buy OC-48 if the local carriers doesn't offer those other lower-bandwidth packages. These SONET connections are correspondingly rather more expensive than OC-3 (or FedEx), if the local carriers even offer these speeds between Site X and Site Y.

Yes, I can speak some Network Guy. :-)

Stephen Hoffman
HoffmanLabs

Re: FTP transfer speed

Wim Van den Wyngaert — Tue, 27 Mar 2007 10:05:38 GMT

Just did some testing. On a deault config an ack is sent for about every 5 packets.
I did ucx set prot tcp/delay on the destination node(was nodelay for Sybase !) and the ack was sent every 20 packets. But this only on a slow alphastation with 10 Mbs and a 20K blocks file.

Redid the test with a 220Kblocks file and then the ratio was 1 ack for every 35 packets.

Wim

Re: FTP transfer speed

Wim Van den Wyngaert — Tue, 27 Mar 2007 10:14:05 GMT

But looking in detail I find that at the end of the ftp sessions an ack was given every 500 packets !!! Most acks were given in the beginning of the session.

Wim (glad my test proved my memory was right)

Re: FTP transfer speed

Hein van den Heuvel — Tue, 27 Mar 2007 10:14:56 GMT

So you used SET PROT TCP/WINDOW_SCALE.
What is the WNDSIZ setting you tried?

Speed of Light = 300KM/ms
400km, round-trip = 3ms... close enough to the 4 - 5 ms delay stated.

If the protocol was entirely synchroneous this would allow for 250 exchanges / second.
So the 72Mb/sec =~ 9MB /sec = 360KB / exchange = 240 packets @1500 / exchange (not counting overheads).

Google for :"window size" latency tcp ftp gives lots of interesting reads of course:

http://www.asperasoft.com/technology/comparisons/gigabit.html

http://www.supercomp.org/sc2002/paperpdfs/pap.pap327.pdf

Cheers,
Hein.

Re: FTP transfer speed

Wim Van den Wyngaert — Tue, 27 Mar 2007 10:36:32 GMT

BTW : my window scale was 61K.

Wim

Re: FTP transfer speed

Wim Van den Wyngaert — Tue, 27 Mar 2007 10:40:54 GMT

But it decreases to 10K during the operation.
So, it's just enough.

Wim

Re: FTP transfer speed

Jan van den Ende — Tue, 27 Mar 2007 12:27:41 GMT

Re Hein:

>>>
Speed of Light = 300KM/ms
400km, round-trip = 3ms... close enough to the 4 - 5 ms delay stated.
<<<

Yeah, common error.
Most glasses have optical density ~ 1.5
That makes the speed of light in such glass ~200KM/ms.... and now you are close to theoretical.

Only way of speeding up is less round-trips, ie., more data per ACK.
(theoretically, the lightspeed in air (close to that in vacuum) can be used, but only by electromagnetic (light, radiom microwave...) along a direct line of sight. That brings a whole lot of other challenges)

hth

Proost.

Have one on me.

jpe

Re: FTP transfer speed

Vladimir Fabecic — Wed, 28 Mar 2007 02:36:35 GMT

Answer from network guy to Hoff:
"The answer to Hoff: WAN link is 2 times gigabit ethernet over DWDM.
Because of the distance (400km), average round trip time is 7 ms (this
is measured by network performance tools)."

He also asks:
"What is the maximum TCP window size supported?"