[UDT] General questions about performance

[Yang <3jl...@sn...>]

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!