VPN - speed query

I have been using Windows Remote to have one home office user access a PC in our office, and it works quite succesfuully. Problem is that they can get to their PC screen OK, but what is actually needed is to have the actual file (eg, Word document) open up on thier home PC, edit it, then save back again to the office network. To achieve that I used Hamachi software, which was simpe enough to set up, and it does work, but at a much slower speed than Windows remote. Is this normal? If so, what is the reasonfor the slower speed, and is there something I can do to change it?

 

With Windows Remote, you are note moving files over the VPN link. Rather you are just controlling the desktop of the remote PC. Passing keyboard, mouse input and screen changes back and forth is surprisingly easy to do and does not consume much bandwidth. Therefore, remote desktop systems work surprisingly well over an internet connection.

If you use VPN to access a remote file system, pull a file over the link, edit it, and then return it, that takes a lot of bandwidth (BTW, opening a file requires the file to be pulled to the local system before it is opened). Especially if you are using an asymmetrical system like ADSL.

For example, in the UK a typical ADSL line would have a download speed in the range of 4 to 8Mb/s However, it is unlikely that upload speed will be greater than 0.5Mb/s. With VPN you typically connect from one broadband connection to another, and therefore every connection is throttled by the upload speed from the sending end of the VPN.

A 0.5Mb/s connection is plenty for remote desktop, but file transfer will be slow.

Personally, I use remote desktop over VPN. That gives me the security of VPN with the efficient use of bandwidth of remote desktop.

 

So its not Hamachi itself - I wouldn't for example get any better results using another VPN software such as Windows XP's own?

 

I would hope that the software wouldn't be the problem. Part of the process of creating a VPN tunnel, is encrypting each packet of date. Encryption does take up processing, and therefore is a performance hit. However, with modern systems its not a big hit, and I would hope that a commercial system would out perform Windows' inbuilt system.

As I said previously, it is more likely to be upload speed that is the problem, unless you have something like a leased line or SDSL connection to the internet.

 

No, no leased lines or SDSL connection.

Home user has 500kb upload speed broadband. Office PC has 1MB upload speed. It took 18 seconds to upload a 813kb Word document from office network to home user via Hamachi. Would that be about right? And if I upgraded Home user to 1MB upload speed (double), would that make it download in half the speed?

Maybe I am misunderstanding the upload and download speeds? Is it the upload speed of the remote computer that is important, or the upload speed of the home user's computer?

 

The improvement will be a little less than half the speed, but significant. At a guess, I would suggest 20% faster.

From office to home, the limiting factor is the upload speed at the office.

From home to office, the limiting factor is the upload speed at home.

However, a lot of network traffic is two way. That is, a request is sent out, and a response is returned. File transfer is one example were this traffic is very asymmetrical. That is, the packets requesting files to be returned, are much smaller than the packets returning the file.

Therefore, increasing the upload speed at home is likely to improve the performance when returning the file to the office.

With the office upload speed, another thing to consider is the amount of traffic that is also trying to use that upload connection to the internet. How many users do you have in the office?

 

4 office users, 1 home user

 

Then unless the 4 are heavy internet users, not a huge problem.

 

I think I AM confused about the difference between upload and download ... ... if the office users are using the internet, are they not using the download speed (for normal surfing I mean) rather than the upload speed?

 

A file being passed from your office follows this path:

Office > Internet > home

So the file is uploaded from the office to the internet. Then downloaded from the internet to home.

A file going the other way follows this path:

home > internet > office

The file is uploaded from home to the internet. Then downloaded from the internet to the office.

 

Download and upload are always coexistence.

For example, even you download a file from internet, there is still some upload traffic for controlling, negotiating etc.

 

If a Word file oopens in 18 seconds, and increasing upload speed to 1MB may speed things up by about 20%, then that still means around 14 seconds to open a document - that is not really going to be workable. Is this normal for a VPN, or is my system hopelessly inadequate? What would I have to do to have the docuemnts open at a close-to-normal speed, or at a speed comparable to Windows Remote?

 

This is normal for VPN over ADSL. File loading is slow. Access to web pages and remote desktop systems work well. Using FTP rather than standard folder sharing is often better as it involves less of an overhead. But it is still slow.