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From André Warnier>
Subject Re: TCP Window Size
Date Fri, 15 May 2009 09:22:47 GMT
Phinux Zhang wrote:
> Hello
> Does anybody know how to change TCP window size in tomcat configuration?
> It's strange that we can get about 200 KB/s bandwidth when downloading from
> FTP service, but it's just about 45 KB/s bandwidth from tomcat service
> located on the same server. I doubt it's a problem a TCP window size, maybe
> we can improve the speed by changing the windows size.
> Thanks in advance for any advices. Please let me know if you need any more
> information.
If you want to get some relevant answers, I suggest that you provide 
much more information about what you are really doing, what you are 
comparing, and how you obtain your bandwidth figures above.

At the general level, I would tend to think that FTP is a program whose 
main function is to download/upload files, while Tomcat is a servlet 
engine; so it is no wonder if FTP would be somewhat more efficient if 
you compare purely on the base of one large file download.
FTP is probably full of tricks to manipulate the window size and packet 
size dynamically, in function of the link performance at any point in 
time.  Tomcat being a much more generic piece of software, I doubt it 
would include the same kind of logic.

I would also think that, TCP window size being a parameter down at the 
socket level, it would be surprising if Tomcat itself had a 
configuration parameter for this. Maybe you will find one at the jvm 
level, or maybe you can, in your application, drill down to the java 
Socket level and set it there.
This being said, I doubt very much that your problem would be at that level.

Another suggestion : set up a comparison between Apache HTTPD and 
Tomcat, both delivering a page with a http link to the file you want to 
download, compare those, and post your comparison here.  That would be a 
much more relevant comparison.
And if you don't get much of a difference that way, then you have your 
answer already.

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