improving transport over lossy links ?

[Ian Smith]

Hi Mike,

On Sun, 21 May 2006 at 16:03:39 -0400, Mike Tancsa wrote:

 > Correct. Its always dialing into a terminal server that is connected 
 > via PRIs. Usually Lucent PM3, sometimes Cisco 5800s depending on the 
 > location they dial from.

I guess you won't want to be messing with their configs, then ..

 > >  > The internal USR seems to correctly see the carrier drop and PPP
 > >  > hence sees it.  However, the 2 external Intels I am experimenting
 > >  > with on the USB serial ports do not. I suspect thats part of the
 > >  > reason the DCD is not working. Perhaps incorrect init string or
 > >  > something with the USB-Serial.  Note, I only have the internal USRs
 > >  > deployed in the field right now
 > >
 > >Don't know about USB modems.  Do USR still use their own chipsets, or
 > >what?  In any case, they're probably highly tunable and well documented.
 > 
 > Actually, they are just regular external modems connected to USB to 
 > serial adaptors (using the uftdi driver)

I had a browse through /sys/dev/usb/{uft,ucom}* but was well out of my
depth .. it =looks= like DCD (aka RLSD) changes should be picked up ok;
perhaps you're right about some odd init string or such - good luck!

 > >Not V.90 full tilt, anyway.  If 45333 is sort of usual for this one,
 > >then I'd probably try telling it to connect no higher than maybe 41333
 > >or 40000; often about 10-15% or so less than 'normal' can make all the
 > >difference.  If you can afford the bandwidth, go for slow and solid ..
 > 
 > 
 > Yes, for sure I will try and lower the speeds a bit, but ultimately I 
 > want to deal with situations where the carrier drops and the modem 
 > has to redial.  The client is willing to put in an extra phone line 
 > if it would make the link more reliable.  Typically these sites are 
 > too remote for other types of transport.  I think if I can get mp 
 > working with reliable dcd I think that should do it.

Fair enough.  Chances of losing two lines at once are pretty small,
unless there are district-wide problems, given you get DCD going ..

cheers, Ian