In article <3fnn4r$
...@info.census.gov>, lr
...@info.census.gov (Lee Rian) wrote:
..Stuff deleted..
>>MTU = 552
>>MSS = 512
>>RWIN = 4096 ## Play with this setting to optimize for your system.
>I thought those settings were selected to give good response time for
>multiple interactive sessions using the same slip line.
>If you've only got one session using the line MTU=1500, MSS=1460 will
>give better performance.
>Lee Rian
>lr...@census.gov
According to the .faq, and some of my own experience (measured with
WS_FTP) the results you get with these settings will vary depending on
what sites are involved in a tranfer.
If you're connecting to *one* site that supports a packet size of 1500
bytes, then you're right...MTU=1500 is optimum. But if you wind up
relaying thru 2 or more sites, say in an ftp from Australia (Likely to
be 30-40 sites ?) then you can't get a packet bigger than the worst case
packet size any one of those relay points will support.
If you request a packet of 1500, and then hit a site that'll do 512, then
your original packet will be segmented into 472 byte packets(4 of em)
and a 40 byte header added to each of them. One of those packets will
be very small...56 bytes plus the 40 byte header.
Since you requested 1500 byte packets, your pc will spend the time
trying to write the 1500 to your hard drive. Now you've increased your
overhead enormously, because your pc is busy doing nothing..waiting
for 1000 bytes of info that doen't arrive in the packet (times 4 packets).
Most international transfers support MSS (Maximum Segment Size)=512.
This allows the settings I quoted above.
My measurable results for the same file transferred many many times
ranged from about 6000 bytes/sec to 1300 bytes/sec on my
486DX2-66 with a 14.4K modem using TIA / WS_FTP/Trumpet
winsock v2.0a/Windows 3.1.
Best results were the above quoted numbers. The worst were the
defaults set in the winsock .ini...MTU=1500/MSS=1460.
Boy..That's the most I've said in six months..Did it make any sense ?
Joe Bradshaw
Boston, Ma.