A Beginner's Guide To WAN Acceleration

[iwod]

I read the WAN Acceleration article and i couldn't understand it.

a 40ms latency between me and the FTP server would means i drop my total throughput from 1Gbps Theoretical Max to 40Mbps?

I am pretty sure i get many times higher then that when i upload or download from FTP with many times higher then 40ms latency.

So what am i missing?

 

[thiggins]

You really have a Gigabit connection to your ISP?

This article may help. It's a bit dated with its references to dial-up modems. But the principles are sound.

 

[onnoossendrijver]

On notorious example is CIFS, the Microsoft file sharing protocol used to access networked drives. CIFS adds another layer that limits how much data can be sent while waiting for acknowledgements

This tells exactly what the problem is: The application waits for an acknowledgement after X sent bytes/packets. During that time the application waits before sending new data to the other side. On high-latency links this adds up very fast.
Smarter applications (like FTP) are better optimized for such high-latency links.
For example they send more data without waiting for acknowledgement.

 

[vnangia]

This is a really good introduction to the problem, but I wonder if there's going to be a second (or third?) part where we discuss some ways to mitigate without investing vast sums of money. Any chance?

 

[iwod]

You really have a Gigabit connection to your ISP?

This article may help. It's a bit dated with its references to dial-up modems. But the principles are sound.

Not to be rude or anything. I try to tell the story there are world outside US which has Internet Speed FAR exceed 100Mbps WAN Port.

Yes I do have a Gigabit Connection to my ISP. And i wasn't uploading to my ISP FTP server either.

Or I am guessing the problem only matters if you are transferring many files which causes acknowledgement time from latency to greatly effect transfer rate?

P.S I will read the article tonight.

 

[thiggins]

This is a really good introduction to the problem, but I wonder if there's going to be a second (or third?) part where we discuss some ways to mitigate without investing vast sums of money. Any chance?

I asked the author that question. The short story is that there are not any WAN acceleration products that are priced for very small business budgets. I will poke at this a bit more, but don't hold your breath.

 

[DC Palter]

Low cost solutions

This is a really good introduction to the problem, but I wonder if there's going to be a second (or third?) part where we discuss some ways to mitigate without investing vast sums of money. Any chance?

There are a number of lower cost alternatives that I've heard of, including a freeware project, but I'm not able to assess whether they work well or not. The only information I have is the same information you'd find with a google search.

However, I think the better alternative is to figure out the best way to implement the application so that it is not as sensitive to the WAN conditions. Let me give an example to explain what I mean - let's say you use Quickbooks for your accounting. And you want to have a part-time bookkeeper login to your office to work on it. Well... that won't work. QB absolutely will not work over a WAN. But there are alternatives - (1) use Quickbooks' cloud-based service instead of the application itself; (2) use Citrix, Remote Desktop, or other VDI to access QB locally on the LAN and run the screen images over the WAN; (3) download the file, run locally, and upload the file; or (4) use a different accounting package better designed for a multi-user environment.

Similarly, some VoIP systems can automatically adjust the codec to different link conditions and some do that better than others.

In a nutshell, if an expensive accelerator isn't worth the cost and you don't want to take a chance on a low-end one, the best solution is to do without a WAN accelerator and engineer the applications to work under your network conditions.

 

[DC Palter]

Theoretical maximums

I read the WAN Acceleration article and i couldn't understand it.

a 40ms latency between me and the FTP server would means i drop my total throughput from 1Gbps Theoretical Max to 40Mbps?

I am pretty sure i get many times higher then that when i upload or download from FTP with many times higher then 40ms latency.

So what am i missing?

The exact numbers depend on the TCP window size settings and the latency, which depend on the operting system and version. The default settings can be adjusted, but few users know how to do so, and the application can override the settings. The basic calculation is:

Max throughput = window size / delay

If you use different machines than me, you'll get different results.

 

[vnangia]

I asked the author that question. The short story is that there are not any WAN acceleration products that are priced for very small business budgets. I will poke at this a bit more, but don't hold your breath.

That's unfortunate. It's exactly those kinds of firms that would get the most use out of something like this. Quantum isn't available for everyone...