Re: [UDT] General questions about performance

[Yunhong Gu <yu...@la...>]

There are many factors that can affect the transfer performance. In 
addition, UDT is not necessarily always faster than TCP, especially on 
long bandwidth environments. I do believe that you can modify the UDT code 
by yourself to reach better performance, unfortunately this requires 
some understanding to the code:)

There are available tools using parallel TCP to boost transfer speed for 
home network users.

Yunhong Gu, Ph.D., Research Scientist

National Center for Data Mining
University of Illinois at Chicago
SEO 700, M/C 249, 851 S Morgan St
Chicago, IL 60607-7045
T (312) 413-9576
F (312) 355-0373

On Tue, 2 Jan 2007, Yang wrote:

> hi all, i tested sendfile/recvfile between two hosts on the same
> university network (~1ms lag), but found the performance to be poor.
> using http, i was able to transfer a 6.6MB file in 7.7s (~860KB/s),
> but this took 17s using udt. one host is linux (just used 'make' to
> build), the other is windows xp (built using visual studio).
>
> i was wondering:
>
> - is this result expected? i realize that my hosts have low latencies,
> but i didn't think this explains the magnitude of the hit...nor that
> the performance of udt would/should in any situation be worse than
> tcp. my understanding is that a primary aim of udt is to maximize
> throughput.
>
> - is there anything (reasonably effortless) i can do to see better performance?
>
> - are there other file transfer apps that do offer improved bandwidth
> usage over tcp? i glanced at some of the papers' related works, and
> the only other released software i found was tsunami (which i have not
> tried).
>
> - is there any reason why i should not expect to find such an app? (i
> have zero background in networking. things i can imagine are:
> userspace implementations have too much overhead to compete with
> kernel tcp stack; isp's/routers prioritize tcp packets, which play
> fairly, over other packets; etc.)
>
> to give some background/a better idea of what i seek: i was ftp-ing
> large files today between two hosts across the US at disappointing
> rates when i got the idea to look into alternatives to tcp. i realize
> that people have long researched protocols and congestion controls to
> maximize throughput, particularly targeting the case of high
> bandwidth*latency. i didn't want to subject myself to too much pain in
> this endeavor (e.g., rebuilding kernels would be going too far), so i
> set about looking on various open-source software sites for real-world
> implementations using udp - and that's how i found udt. i haven't
> found any other apps, though (except for tsunami, but i imagine that
> udt is an improvement thereon).
>
> thanks very much in advance!
>
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