SLOW Window over PPP

SLOW Window over PPP

Post by Patrick Mart » Mon, 01 Jan 1996 04:00:00



It takes forever for a window to transport over a phone line
from one machine to another--I have PPP running and aa 14.4 modem.
I had this same problem with WIN32 with an X emulator--I thought
this would improve with Linux but no. Does anyone know why?
Is the memory to generate a window just too huge to transport over
a phone line? It negates even having x runnign on multilpe machines unless
they are all connected via ethernet.
pc martin

 
 
 

SLOW Window over PPP

Post by Randy Chapm » Tue, 02 Jan 1996 04:00:00


14.4 modems.. modems in genera, actually.. have this thing called latency.
The minimum time for a request to go from one end of the modem, get answered
and come back is on the order of 300ms on a good day.. more like 500-750
normally.  Thats about the same amount of time it takes to go to Sweden
from the US and back, to put it in perspective.

This makes the starting of X apps over a modem painfully slow.  Things like
xterms I've found to be quite useable over a 14.4 .. almost as good
as local xterm+telnet.  But Mosaic takes 5-10 minutes to start up...

Dont expect to run X apps regularly over the 14.4 .. maybe with lbx, it would
help.. ut I've never gotten that to work =(

--randy

: It takes forever for a window to transport over a phone line
: from one machine to another--I have PPP running and aa 14.4 modem.
: I had this same problem with WIN32 with an X emulator--I thought
: this would improve with Linux but no. Does anyone know why?
: Is the memory to generate a window just too huge to transport over
: a phone line? It negates even having x runnign on multilpe machines unless
: they are all connected via ethernet.
: pc martin


 
 
 

SLOW Window over PPP

Post by strip » Wed, 03 Jan 1996 04:00:00




>This makes the starting of X apps over a modem painfully slow.  Things like
>xterms I've found to be quite useable over a 14.4 .. almost as good
>as local xterm+telnet.  But Mosaic takes 5-10 minutes to start up...

I don't have that problem.  I did for the longest time, but I was told
if you turn off vj compression, things will speed up.

Quote:>Dont expect to run X apps regularly over the 14.4 .. maybe with lbx, it would
>help.. ut I've never gotten that to work =(

Try running pppd with the parameter -vj.


>: It takes forever for a window to transport over a phone line
>: from one machine to another--I have PPP running and aa 14.4 modem.
>: I had this same problem with WIN32 with an X emulator--I thought
>: this would improve with Linux but no. Does anyone know why?

This is not a memory problem at all.  I just upgraded my linux to
1.2.13, and I had to reinstall pppd and chat.  I discovered my
telnet sessions were timing out on me.  Talk about frustrating!

Anyway, I talked with lots of people, and I thank them all :) and
a freind of mine told me to turn off compression.  He told me that
in any platform, including your messy windoze, turn off vj compression.

In Linux, it's

pppd -vj

I don't know what the windoze setting is.  

Quote:>: Is the memory to generate a window just too huge to transport over
>: a phone line? It negates even having x runnign on multilpe machines unless
>: they are all connected via ethernet.

Try that, and lemme know what happens, I'm curious to see :)

////stripes////
--

  -  /\,  Only by attempting ) o   >.~.\ `` ` `,`,`. ,'_'~`.      
 -  -|~(*)  the absurd can   )    (v_," ; `,-\ ; : ; \/,-~) \          
-  (*)        we achieve the )     `--'_..),-/ ' ' '_.>-' )`.`.__.')
^^^________     impossible! )     ((,((,__..'~~~~~~((,__..'  `-..-'fL

 
 
 

1. If you have slow ppp of compressed files try smaller Window

I have a theory that many people who are experiencing stalling and
slow ftp of highly compressed files can benifit by using a smaller
Window.  If you are having this problem please try the following after
getting ppp up:

                 /sbin/route del default dev ppp0
                 /sbin/route add default window 16384 dev ppp0

Please let me know if this helps or not.

The Theory: (and the theory is this :-)

(I just finished reading the relevant RFS's yesterday, so be gentle
with me :-)

1. The ftp server sends your entire Window in one "belch", and your
ISP buffers it while it gets doled out over the modem.

2. In order to save a buck on RAM, the ISP's equipment (probably the
Portmaster) is trying to compress the DATA.

3. Along comes a packet which poisons their compression algorithm, and
everything breaks (probably by unexpectedly over-using your allocated
resources).  From then on the TCP/IP flow control and retransmission
algorithm is hopelessly broken.

Using the small window will prevent you from overflowing their buffer
even with a compression poisoning packet.

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