Want to protect your cyber security and still get fast solutions? Ask a secure question today.Go Premium


Dial-up networking/ppp binary transmissions slowing down and freeze

Posted on 1998-12-09
Medium Priority
Last Modified: 2010-03-18
Keywords: Dial-up networking/ppp transmissions slowing down and freeze
Summary: through my best ISP - PPP binary transmissions slowing down
Program: pppd 2.3.3 - dip 3.3.7o - kernel 2.0.35
Hardware: Intel Pentium 133  16 MB RAM  Rockwell K56Flex modem  2.1 GB EIDE HD
          UART 16550A
Description: I dial into my ISP successfully but binary transmissions slow down
like images , FTP , ETC

The problem is that after I connect to my ISP and I surf the
transmissions of binary data (pictures, compressed files, etc.) is
slower and slower and it goes with 242 bytes/sec - horrible at any site
at any time with any protocol.
But the ISP is working well under other OS-es and when I phoned them ,
they could only tell me that the modems are system
independently configured. (They run SunOs)
One of the other ISPs I tried runs perfectly, but the best is that I
want to fix.
The PPP debug from the working ISP file differs in only one thing from the
want I want to use is that the good one sets MTU to 576 no matter what
I use in ppp options file and the other one sets MTU 1500 automatically, which
can't be changed , too.
I use a Pentium-133 PC with a modem based on Rockwell  K56Flex Chipset.
I use 2.0.35 kernel with pppd 2.3 p3.
I use dip (since chat does not work correctly) to access my server, I
include the script at the end.
I've alredy tried:
-setting up the  ports correctly with setserial
- there's no shared IRQ, I use IRQtune to optimise the system
- setting pppd options (on and off) (like asyncmap 0 ,nobsdcomp+novj,-detach,
-Trying out different MTU-MRU, Window size values
- The phone line's quality is good. I always log in with >=28.8 as in
Windows.  The modem Init script is good.

Please e-mail me or post a message if you have any more suggestions.

  ViZo - vizo@usa.net

-----------------DIP Script -------------------
       port cua1
       speed 115200
       shell setserial /dev/cua1 uart 16550A spd_vhi port 0x2F8 irq 3
       shell /sbin/irqtune
       get $mtu 1500
       send AT&FE0V1&C1&D2S95=47S0=0\r
       # send AT&K3\r
       wait OK 5
         if $errlvl != 0 goto modem_trouble
         dial 1234567
        if $errlvl != 1 goto modem_trouble
         sleep 2
         print Waiting for login prompt...
 wait Username: 20
         send xyz\r
         wait assword: 20
         send xyz2\r
         send ppp\r
         wait is 20
         get $locip remote 20
         wait is 20
         if $errlvl != 0 goto ppp_error
         print IP $rmtip
         print CONNECTED $locip
         print MTU: $mtu
         mode ppp

         print The modem connection failed
         goto error

         print TIME-OUT waiting for PPPlogin to fire up...
         goto error

         print time-out waitin for ppp message
         goto error

         print CONNECT FAILED to $remote
         quit 1

Expected: Stable binary transmissions speeds.
Question by:vizo2

Expert Comment

ID: 1587844

If I understand all of the above correctly, you are having trouble with one ISP, and things work well with another ISP?


Expert Comment

ID: 1587845
Slow down your serial port. Or upgrade your RAM. Or both!
Your machine is being flooded with information and your machine can't handle it.
Try some different,slower speeds and see what this does.


Author Comment

ID: 1587846
I've already tried to slow down the serial ports and the connection, it doesn't use. And it doesn't explain why other ISP's do work perfectly. I'm not silly. I would change my ISP , but the one I use is free and good. Because my linux workstation
is configured now well and I want to use it for networking , too.
They use SunOs 5.6 but they can't explain the situation.
Thank you for your answer. And please help me.


Modern healthcare requires a modern cloud. View this brief video to understand how the Concerto Cloud for Healthcare can help your organization.


Expert Comment

ID: 1587847
i got same problem on my a few linux(s). excetly the same. i also want to know the answer.



Expert Comment

ID: 1587848
Try dialing one of the ISPs numbers long distance.  If it speeds up, then your telco has a bad switch.  What kind of equipment is the ISP using on their end?

Also you might want to check the manual and turn data compression off.

Always add the time tested AT&F1&C1&D2

Try adding +MS=11,0,9600,33600 and try setting that last value lower and lower (i.e. 28800, 26400, 14400, 9600, etc)

But in my opinion, it's either a set of equipment that doesn't like each other (like USR and Ascend), or a telco screw up.

Author Comment

ID: 1587849
I use the same init string as in windows the perfect fo v.34 -mnp5,..
I also tried every combination and turning off compression methods.
The starnge thing that it's working well under other OSs and I use the perfect init code.
Other local-numbered ISPs work well.
And I don't know why the hell it is working under Windows perfectly and not under Linux.
But, anyway thanks for your answer but I tried to slow down the speed at 24000 , too, while others running at 26 <= are running cool.

Thank you,

Author Comment

ID: 1587850
the ISP use Sun Solaris 2.56 based machines with 28.8 US Robotics modems.
I think it must be a bug between the two systems.

Expert Comment

ID: 1587851
Change the PPP daemon with ppp-2.3.5. This PPP work great and I think I saw kinda problem with ppp-2.3.3 and linux kernel 2.0.3x.

Author Comment

ID: 1587852
I've alredy tried it (as I've written down), and it is bad with linux 2.1.1, too. It doesn't work with other systems too, with only one it does but that's the worse service.


Expert Comment

ID: 1587853
Alan Cox, who is responsible for most of the networking code
of linux, has reported a "slow network connection problem"
between linux and solaris:


He writes:
Slow FTP Linux<->Solaris 2.4 or 2.5
     Solaris has some very bad TCP problems over slow links. Sun have now released a patch set for Solaris 2.5
     103447-03 and 103169-06 (ftp://sunsolve1.sun.com/pub/netpatches )

also the same document mentions a problem due to MTU mismatch

Sessions work but the first large output hangs the link
     This is often seen over SLIP links when path MTU
     discovery is used. Previously you could normally get
     away with mismatched MTU's at each end of a slip link
     to Linux boxes. With Path MTU this is no longer true.
     Fix the MTU's. Also beware of some very old terminal
     servers that mishandle MTU discovery. If so turn
     MTU discovery off or use 1500 byte+ MTU's
     on the slip link.

The first one is related to your ISP (do they have the
patch installed?)

The second one is I think more likely in your case
you can try setting your MTU to be the same as used by
your ISP (576)

or try disabling MTU discovery
I am not sure how but
there may be a related setting in /proc
or you may have to recompile your kernel
(with relevant options)
try checking the kernel source/documentation

hope this helps...



Accepted Solution

tfabian earned 2000 total points
ID: 1587854
you can fiddle with increasing your window and buffer sizes, but for it to really make a difference, you need to get your ISP to do it too..

check out url


for details..   it explains how you can performance tune almost any tcp implementation to achieve maximum throughput on slow networks..

good luck


Featured Post

Concerto Cloud for Software Providers & ISVs

Can Concerto Cloud Services help you focus on evolving your application offerings, while delivering the best cloud experience to your customers? From DevOps to revenue models and customer support, the answer is yes!

Learn how Concerto can help you.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

I have seen several blogs and forum entries elsewhere state that because NTFS volumes do not support linux ownership or permissions, they cannot be used for anonymous ftp upload through the vsftpd program.   IT can be done and here's how to get i…
Note: for this to work properly you need to use a Cross-Over network cable. 1. Connect both servers S1 and S2 on the second network slots respectively. Note that you can use the 1st slots but usually these would be occupied by the Service Provide…
If you're a developer or IT admin, you’re probably tasked with managing multiple websites, servers, applications, and levels of security on a daily basis. While this can be extremely time consuming, it can also be frustrating when systems aren't wor…
Look below the covers at a subform control , and the form that is inside it. Explore properties and see how easy it is to aggregate, get statistics, and synchronize results for your data. A Microsoft Access subform is used to show relevant calcul…
Suggested Courses
Course of the Month13 days, 5 hours left to enroll

580 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question