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ISDN external TA - getting only 64k of 128k - Linux Setup, Configuration & Administration

We have a D-Link 128K external TA connected to a P-IV system running RedHat Linux 8.0 (kernel 2.4) using serial comms port (16550 UART). At present i connect to the inet by manually dialling the TA using minicom and then running pppd -detach /dev/ttys0. Whatsoever i've done, i m unable to get 128K Rx speed. The average Rx is just around 52k - 60kbps (6-7KBps). The TA supports 128K for which i've to use AT%A2=6 (MLPPP), also the portspeed is set to 230400bps in the pppd options, which the TA supports. The dial command : ATD172225 and my ISP uses ...

  1. #1

    Default ISDN external TA - getting only 64k of 128k

    We have a D-Link 128K external TA connected to a P-IV system running
    RedHat Linux 8.0 (kernel 2.4) using serial comms port (16550 UART). At
    present i connect to the inet by manually dialling the TA using
    minicom and then running pppd -detach /dev/ttys0. Whatsoever i've
    done, i m unable to get 128K Rx speed. The average Rx is just around
    52k - 60kbps (6-7KBps).

    The TA supports 128K for which i've to use AT%A2=6 (MLPPP), also the
    portspeed is set to 230400bps in the pppd options, which the TA
    supports. The dial command : ATD172225 and my ISP uses PAP
    authentication (pap-secrets - OK). While i have no problems while
    connecting or afterwards, the connection is stable but the only
    bottleneck is the 60k downlink that i m getting.

    I've calculated the Rx throughput by checking the /var/log/messages to
    record the pppd startup time and the ifconfig to record the Rx data
    received (in BYTES and not bits). ifconfig ppp0 reports no or very few
    (2-5) packet errors. About 50-60 WinXP clients have been configured to
    access proxy services which squid (2.5 stable) provides.

    When i tried ATD172225&172225, the TA reported error. I tried putting
    spaces around & but couldn't suceed. I have no telephones connected to
    the TA. But when i connected a phone to both the ports 1 after
    another, i found both the lines busy (silence). intrestingly, as
    mentioned in the manual "the BACP/BOD functionality will automatically
    freeup 1-b channel when the user picks up the receiver" i didn't get
    any such result. both the lines remain silent without getting any
    dailtone. Are bot the channels really being used? This setup is at
    our college. I've convinced the admin there to use linux+squid over
    WinXP+NAT. the performance is better in linux as compared to WinXP but
    Rx still is low on both the OSes.

    The responses I receive after entering AT commands are :
    PROTOCOL : MLPPP 128k
    CONNECT 230400

    I've tried using a shell script "pppd connect 'chat -v ......" for
    connection. but all in vain.

    what am i missing? is anything wrong?
    ready to post ne other required details,
    just ne suggestions are welcome.
    thnx in advance

    - uday

    ================================================== ====================================
    The next rock solid M$ OS :: Windows CE + Windows ME + Windows NT =
    Windows CeMeNT
    ================================================== ====================================
    Uday Guest

  2. #2

    Default Re: ISDN external TA - getting only 64k of 128k

    Uday wrote:
    >
    > We have a D-Link 128K external TA connected to a P-IV system running
    > RedHat Linux 8.0 (kernel 2.4) using serial comms port (16550 UART). At
    > present i connect to the inet by manually dialling the TA using
    > minicom and then running pppd -detach /dev/ttys0. Whatsoever i've
    > done, i m unable to get 128K Rx speed. The average Rx is just around
    > 52k - 60kbps (6-7KBps).
    >
    > The TA supports 128K for which i've to use AT%A2=6 (MLPPP), also the
    > portspeed is set to 230400bps in the pppd options, which the TA
    > supports.
    [snip]
    > I've tried using a shell script "pppd connect 'chat -v ......" for
    > connection. but all in vain.
    >
    > what am i missing? is anything wrong?
    It sounds like you're missing multi-link support (i.e., only one channel
    is being used). Are you passing the "mp" or "multilink" options to pppd
    when you try to connect? Have you read the "MULTILINK" section in 'man
    8 pppd'? (AIUI, you need to connect twice with two instances of pppd so
    that multilink will bind the two channels together.) Does your kernel
    include "Multilink PPP" support?
    John-Paul Stewart Guest

  3. #3

    Default Re: ISDN external TA - getting only 64k of 128k

    Problem may also be at your ISP ... Some ISPs do not support multilink
    especially on unmetered dialup numbers .. This is as you are tying up two
    lines and they are having to pay for two freephone lines instead of one ..

    Regards,

    Phil.
    "John-Paul Stewart" <jpstewartsympatico.ca> wrote in message
    news:3F48D6D7.17941B6Esympatico.ca...
    > Uday wrote:
    > >
    > > We have a D-Link 128K external TA connected to a P-IV system running
    > > RedHat Linux 8.0 (kernel 2.4) using serial comms port (16550 UART). At
    > > present i connect to the inet by manually dialling the TA using
    > > minicom and then running pppd -detach /dev/ttys0. Whatsoever i've
    > > done, i m unable to get 128K Rx speed. The average Rx is just around
    > > 52k - 60kbps (6-7KBps).
    > >
    > > The TA supports 128K for which i've to use AT%A2=6 (MLPPP), also the
    > > portspeed is set to 230400bps in the pppd options, which the TA
    > > supports.
    >
    > [snip]
    >
    > > I've tried using a shell script "pppd connect 'chat -v ......" for
    > > connection. but all in vain.
    > >
    > > what am i missing? is anything wrong?
    >
    > It sounds like you're missing multi-link support (i.e., only one channel
    > is being used). Are you passing the "mp" or "multilink" options to pppd
    > when you try to connect? Have you read the "MULTILINK" section in 'man
    > 8 pppd'? (AIUI, you need to connect twice with two instances of pppd so
    > that multilink will bind the two channels together.) Does your kernel
    > include "Multilink PPP" support?

    Phil Ellett Guest

  4. #4

    Default Re: ISDN external TA - getting only 64k of 128k

    Uday wrote:
    >
    > We have a D-Link 128K external TA connected to a P-IV system running
    > RedHat Linux 8.0 (kernel 2.4) using serial comms port (16550 UART). At
    > present i connect to the inet by manually dialling the TA using
    > minicom and then running pppd -detach /dev/ttys0. Whatsoever i've
    > done, i m unable to get 128K Rx speed. The average Rx is just around
    > 52k - 60kbps (6-7KBps).
    I don't know current details for external isdn cards but at the time I
    made my desicion, the situation was as follows:

    ISDN provides 2 communication lines of 64000 bits/second (the B channels
    used for communication) and 1 line of 16000 bits/second for connection
    setup and such, optionally to be used for communication. In the end, all
    communication goes over 2 wires in the connection. The 2 lines can each
    be used for data (full 64000 bits/second) or for speach (and fax,
    ogue modum emulation and such). btw: you never know which link is
    used and who cares, in the end they go over the same line.

    Internal ISDN devices are seen as network cards. The connection is
    handled buy hisax, the isdn driver for linux, it can do channel bundling
    and such. The data stream still goes like a network connection, only at
    64.000 or 128.000 bits/second. Details: there are 8 bits used in a byte
    hence 8.000 bytes per second is (theoretically) possible. Then, I don't
    use kbits and kBytes here since K = 1000 with telco-protocols and K=1024
    with comuter protocols, which can make a difference...

    External ISDN devices (with serial connection to computer) act as modems
    to the PC (at... command set) but retranslate that to the data line. The
    computer just sees a modem that can do a 'high' speed. Over the (single)
    isdn data line, there goes 64.000 bits/second, 8.000 bytes/second. Over
    the serial line between the ta and the computer, goes the 8000
    bytes/second but in a 10 bits/byte hence using 80.000 bits/second. Add
    to that the handling of the modem, like the xon-xoff handshaking for the
    buffers and such and you see there is not much room for aditional data
    while aproaching the limit of the uart (115000 bits/second?)

    Hence, there is not much gain in channel bundling, handled by an
    external isdn-ta. Except when fitted with an additional serial
    connection. So it is save to say that your external TA cannot handle
    channel bundling, except if it is fitted with an other serial
    conneciton. Then, from the computer side, just hook that one to an other
    serial port in your machine and define an other modem and use channel
    bundling as if using multiple modems.

    So if you like to use channel bundling, best use an internal isdn
    device. THe cheapest ones (passive isdn) are the best. I just bought an
    other one for 30 euros, doing just what I like.
    >
    > The TA supports 128K for which i've to use AT%A2=6 (MLPPP), also the
    > portspeed is set to 230400bps in the pppd options, which the TA
    > supports. The dial command : ATD172225 and my ISP uses PAP
    > authentication (pap-secrets - OK). While i have no problems while
    > connecting or afterwards, the connection is stable but the only
    > bottleneck is the 60k downlink that i m getting.
    .... I've never seen those devices, then again, once I found even the
    most basic internal device (now long gone Teles 16.3 cards) can do
    decent channel bundling, I never looked at external devices...
    >
    > I've calculated the Rx throughput by checking the /var/log/messages to
    > record the pppd startup time and the ifconfig to record the Rx data
    > received (in BYTES and not bits). ifconfig ppp0 reports no or very few
    > (2-5) packet errors. About 50-60 WinXP clients have been configured to
    > access proxy services which squid (2.5 stable) provides.
    >
    > When i tried ATD172225&172225, the TA reported error. I tried putting
    > spaces around & but couldn't suceed. I have no telephones connected to
    > the TA. But when i connected a phone to both the ports 1 after
    > another, i found both the lines busy (silence). intrestingly, as
    > mentioned in the manual "the BACP/BOD functionality will automatically
    > freeup 1-b channel when the user picks up the receiver" i didn't get
    > any such result. both the lines remain silent without getting any
    > dailtone. Are bot the channels really being used? This setup is at
    > our college. I've convinced the admin there to use linux+squid over
    > WinXP+NAT. the performance is better in linux as compared to WinXP but
    > Rx still is low on both the OSes.
    Best you can do is get an internal isdn device. It avoids all the ppp
    and modem stuff and can do just what you like at the klick of a button.
    In the linux world, SuSE is one of the developers of the isdn drivers,
    hence you get state of the art with a SuSE distribution.
    >
    > The responses I receive after entering AT commands are :
    > PROTOCOL : MLPPP 128k
    > CONNECT 230400
    >
    > I've tried using a shell script "pppd connect 'chat -v ......" for
    > connection. but all in vain.
    >
    > what am i missing? is anything wrong?
    > ready to post ne other required details,
    > just ne suggestions are welcome.
    > thnx in advance
    >
    > - uday
    >
    > ================================================== ====================================
    > The next rock solid M$ OS :: Windows CE + Windows ME + Windows NT =
    > Windows CeMeNT
    > ================================================== ====================================
    Corné Beerse Guest

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