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Limited bandwidth through https application?

We have an application that runs through IIS on a Server 2008R2 box. It sends .tif and .pdf files to/from clients that can be located anywhere in the world. We are finding that no matter what the actual client's bandwidth is the file transfer speeds top out at about 1.2 mb / sec.  I need ideas on what may be causing the bandwidth crunch or how to troubleshoot this.

Test scenario :
I placed a 50mb test file as a hyperlink on a website hosted by that server. Downloading it from our office seems to peak at about 1.2 mb /sec xfr rate no matter where I try the download from via the internet.

Details :
Our office has gobs of bandwidth. Hundreds of megs of internet pipe. Our server sits behind Cisco routers and an F5 load balancer with an f5 pool set up for each server in our environment.

Our app is a .NET app running through a .NET v2.0 Integrated pipeline Application Pool.
I've run the tests from our offices in Atlanta, Seattle, and Texas. All show results in the 900k-1.2mb/sec when traversing over the internet pipe.
Checked IIS and there are not limits set for bandwidth for the site hostingour test files.

Please let me know if you need any more details.
1 Solution
Dave BaldwinFixer of ProblemsCommented:
Transfers are limited by the slowest section of the path.  900k-1.2 MByte/sec xfr rate equates to a 10Mbits per second internet connection.  Is that what you have?
JasonLattinAuthor Commented:
The internet pipe at our offices range from 30mb to 100mb.
I believe they are 30mb, 50mb, and 100mb at the office I tested from.
Dave BaldwinFixer of ProblemsCommented:
You have 3 different internet connections?
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JasonLattinAuthor Commented:
Tested from three different offices.  Central datacenter with many offices across the US.
Server live in the datacenter and each office has it's own route out to the internet.

I am a hardware guy and don't know much about IIS. I just see a problem and hope to find a fix here. Could be with my F5 setup. Could be IIs settings. I have no idea at this point.
Dave BaldwinFixer of ProblemsCommented:
That's more complicated than anything I've used.  Click on "Request Attention" to get more zones (particularly Networking) added to your question and get others to look at it.
What is the bandwidth at the server location?

Which model F5's do you have?

Is the F5 doing SSL offload or just passing the traffic through?

If doing SSL offload, what is your SSL tps license?
btanExec ConsultantCommented:
most probably you are using one without F5 Web accelerator and likely LTM. Do check out the checklist in the F5 DG for IIS (see the "Appendix C: Manual configuration table") on the profile config loaded. Note that tcp profile has customised version also:

tcp-lan-optimized - This profile is useful for environments where a link has higher bandwidth and/or lower latency when paired with a slower link.

tcp-wan-optimized - This profile is useful for environments where a link has lower bandwidth and/or higher latency when paired with a faster link.

JasonLattinAuthor Commented:
FYI... I am running these questions by our F5 people. I don't manage that box but the ideas that GILTJR and BREADTAN mentioned seem promising. Please give me a day or two to gather up this info and I'll update my posting.
JasonLattinAuthor Commented:
Sorry for the late response to this.
the issue turned out to be an issue in the F5 code itself I am told. The version we are on didn't properly adjust TCP window sizing and it was messing with our internet speeds. they have given us a "hotfix" and it almost doubled the speed we have been seeing. It was an issue inside the code of the F5. Not something we can configure.

Thank you to everyone who helped.
JasonLattinAuthor Commented:
Issue wasn't related to anything we can change. A firmware update of the F5 helped this problem.

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