| T.R | Title | User | Personal
Name | Date | Lines |
|---|
| 2958.1 | re-formatted to 80 cols, & possible answer. | snooty.uvo.dec.com::TRAVELL | John T, UK VMS System Support | Sat Mar 22 1997 08:52 | 17 |
| >Is aboout 2400 char per second a good transfer rate on a 28.8 modem connection.
>It seem like I should be able to get more than that.
It's not too bad, on the serial line to an external modem. each character is
8 bits + 1 start bit + 1 stop bit = 10 bits. 2,400 x 10 bits = 24K bits/sec
Allowing for the modem compression providing a net increase, but other network
bottlenecks obstructing your traffic before it gets to the modem, and noisy
phone line causing modem corrections to be negotiated, this may about the best
you can get.
If you have a super clean line, and a low-traffic path from modem to system each
end, you may be able to improve on this.
Check your port properties to see if the port is set to the highest speed it
will support. If not, the serial line pc <> modem may be a limiting factor.
JT:
|
| 2958.2 | | BHAJEE::JAERVINEN | Ora, the Old Rural Amateur | Sat Mar 22 1997 09:30 | 7 |
| re .1: No start/stop bits with 28,800 modems (the transmission between
the modems is synchronous) - the theoretical maximum is very close to
3600 bytes/sec (without compression).
I often get something like 3,500 on a good phone line, without
additional bottlenecks.
|
| 2958.3 | | WRKSYS::INGRAHAM | Andy | Sat Mar 22 1997 13:31 | 11 |
| ... But you do need to know whether you're actually getting 28.8 kbps
connections, and keeping them throughout the call.
My 33.6 modem usually doesn't negotiate an initial line speed as high
as 28.8. 26.4 (I think) is very common though. I program my modem to
report the actual modem-modem rate when it connects (this has been
discussed several times in other notes).
The average effective transfer rate I get, which may be either greater
or less than 2.88kByte/s, depends a lot on what type of data is being
moved, and what else is happening particularly on the other end.
|