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Thread: IP link Quantar V.24 systems using RAD IPmux-2L Access Gateways

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    Default IP link Quantar V.24 systems using RAD IPmux-2L Access Gateways

    Hi All.

    Seeing as there has been significant progress in this area, due to some prolific contributors on this board, I thought I would add my own implementation of Quantar V.24 linking over IP. This solution uses off the shelf RAD IPmux-2L devices which are designed for transporting TDM signals over IP. The IPmux-2L can transport various versions of serial (V.24 Synchronous being one of them) in addition to E1/T1 traffic. I was fortunate enough to borrow a few of these devices in order to figure out how to configure them, so that I can link two 70cm Quantars in back to back RT mode.

    This guide is a work in progress, so please excuse it if it looks a bit quick-and-dirty (for this first iteration I purely want to get the information out there. I will polish it later.)

    The IPmux-2L device has more info at the manufacturers page here :- http://www.rad.com/10/TDM-pseudowire...-gateway/6132/ These devices have an RRP of about $750 or so, but they have been seen cheaper on eBay. If you are looking to buy some of these, you need to make sure that you get the HS V.24 units. They are set up from the factory to support a specific serial mode and it doesn't appear to be re-configurable by the end user.

    The first thing to do was to get into the devices via the serial terminal. The back of the device ha a 9 pin Serial port labelled CONTROL/DCE. This is the terminal port that is used to perform the initial configuration of the device. The standard serial settings are slightly different to normal - they are 115200/8/N/1. I used PuTTY (http://www.chiark.greenend.org.uk/~sgtatham/putty/) with a simple USB to serial adaptor to get into the device. After the device has booted and you are logged in, The first step is to enter the configuration menu. I have taken these screenshots from the web based management interface, but don't worry - the Serial Terminal menus are identical, just without the pretty graphics

    1) Log in to the RADmux via the web interface or the serial terminal connection

    2) Enter the Configuration menu:-

    Untitled.png

    3) Enter the System Menu:-

    2.png

    4) Click on Host IP and enter a management Host IP address – this is for SNMP management and Web Interface Management access.

    4.png

    5.png

    5) Go back to the Host IP menu, then enter the Service Host IP menu. Enter a Service Host IP address. This is the IP address that carries all the “pseudowire” traffic – this is the TDMoIP traffic that transports the E1/V.24 traffic over IP.
    5.png

    6) Enter the Configuration>System>System Clock menu and select Internal Master clock.

    6.png

    7) Enter the Configuration>Physical Layer>TDM menu and set admin status to disable. We are not using E1 so this can be disabled.

    7.png

    8) Enter the Configuration>Physical Layer>HS Menu. HS is High Speed Serial. This is the V.24 port that we need to configure. Note the clock mode is set to DCE. This is "Data Circuit-Terminating Equipment" and refers to the MODEM itself - in this instance the RADmux itself.

    This means that the RADmux is generating the Tx and Rx clock signals for the Quantar itself. The Quantar will need to have its wireline V.24 board to set to enable "External Tx clock" in its codeplug, and ensure that switch S101 on the V.24 TTN4010 card is set for External Tx clock - also called Microwave configuration.

    Set the menus in the RADmux as follows:-

    8.png

    9) Enter the Configuration > Connection Menu. This is where the actual TDMoIP “bundles" are configured. These bundles are used to transfer the V.24 traffic. The Destination IP address is where we configure the IP of the target RADmux device that is the far end of our V.24 link. It is hard to see, but the “DS0 Bundle“ text is actually a hyperlink to configure the bundle parameters:-

    9.png

    10) Click on the DS0 Bundle link and this will enter the bundle configuration menu:-

    10.png

    11) Change the Bundle Port from TDM to HS (i.e. from E1 to Serial V.24):-

    11.png

    12) Enable all Time Slots for this bundle, since we are using the RADmux for only one link we can use all the bandwidth available:-

    12.png

    13) The Configuration>Connection menu will now look different and have many more configuration parameters available:-

    13.png

    14) Set the Destination IP address to the Service Port IP address of the remote end RADmux set the connection Status to Enable, set the Far End Type to Unframed/HS, and set the Jitter buffer as required (I set it to 32ms – This is what was configured with originally as this is the link latency between the two sites on the IP microwave network). Click Apply:-

    14.png

    15) The pinout for the V.24 connection on the back of the RADmux is as follows. This diagram represents the FEMALE connector on the back of the RADmux (i.e. the DCE) A Male 25 pin to RJ45 female adaptor plugs into this port, and the RJ45 pins are connected to the numbers on the right hand side of the diagram. As per the clocking software configuration setup in step 8, note that since this connector is on the RADmux itself, both the Tx and Rx clock lines are the transmit (output) lines. Pin 15 is the Tx clock output line, and Pin 17 is the Rx clock output line. This is the correct wiring configuration for the Quantar External Tx Clock setup and is typically used with Microwave links or TeNSr Channel banks etc. Note that Pin 24 is not connected - this is the Tx clock input line to the RADmux, whcih would be used if the Quantar was set for Internal TX clock, however the RADmux does not support this mode of operation. The RADmux will only work as the master clock and Quantar as slave.

    Connect one end of a straight through RJ45 Ethernet cable to the 25 pin to RJ45 adaptor, and the other end to the V.24 socket 1 on the front of the Quantar.

    15.png


    On the back of the IPmux-2L, the connectors are as follows, from the left - Power, E1 RJ45, two RJ45 Ethernet ports, and the 25 pin HS (High Speed Serial) V.24 connector. The RS232 9 pin connector is obscured by the 25 pin to RJ45 adaptor in this picture:-

    IMG_0048.jpg

    From the front, they look just like a regular ADSL/cable MODEM:-


    IMG_0049.jpg

    And finally, the best bit is when the AUX/V.24 lights on the Quantar go solid green and the link is up...

    IMG_0051.jpg

    Cheers,
    Matt
    Last edited by MattSR; Nov 13, 2013 at 10:47 PM.


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    It's nice they offer UDP transport, Cisco STUN seems to be only possible via TCP.
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    Hi Guys,

    I have updated the post with information on the clocking configuration. Points (8) and (15) have been updated to explain the V.24 clocking configuration and explains why External Clock must be set up on the Quantar.

    Cheers,
    Matt

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    That's what I call 'Option 2 Quantar TX clock in' adapter config in the Cisco thread. It's the mode to use when the DCE (modem/mux/channel-bank/router) will not accept a DTE supplied transmit clock, AKA serial clock transmit external (SCTE) or external transmit clock (XTC) from pin 24.

    Otherwise the technically 'better' option, if supported by the DCE, is Mode 1 like this:

    t1_0511.gif


    Mode 1 allows for either clock skew or a larger offset between the subscriber radio internal bit rate clock and the core network clock.

    By the way S101/102, S1 and S2, are designed to support DCE or crossed over (local) DTE connections. S1 actually opens the connection between the modem CTS output and the Quantar CTS input while S2 connects the Quantar CTS input to the Quantar's RTS output. There are three combinations:

    S1 and S2 open: Quantar sees CTS off all the time (internal pull up to +5V on WL board)
    S1 closed, S2 open: Quantar sees CTS from DCE
    S1 open, S2 closed: Quantar see CTS driven by own RTS output
    S1 closed and S2 closed: not valid

    According to the Quantar Instruction Manual, S1 should be closed and S2 open is for connection to 'microwave system' (DCE backhaul). S1 open and S2 closed is for 'local connections' i.e. DTE to DTE. The first option is fine in local hook ups as long as RTS and CTS are either looped or preferably crossed over en route to the DIU or peer Quantar.
    Last edited by Astro Spectra; Nov 14, 2013 at 10:38 AM.
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    Hi ASTRO Spectra,

    Just to clarify my understanding, this is how it seems to work in my mind - At a high level, it appears like option 1 allows the whole system to be driven from the subscriber radios clock, as opposed to the "core network" clock. This means that everything runs in the one clock domain provided by the radio, so there are no "slips" or timing issues.

    Option 2 forces the Quantars and subscriber radios (and DIUs etc) to all take their timing off the E1/T1 core network clock, so if there are any discrepancies, eventually there will be a "slip"

    The RAD devices are primarily designed to run E1/T1 traffic over IP, so my guess is thats the reason the RAD devices are configured to only provide the clock, as the real E1/T1 circuits work in this manner.

    Cheers,
    Matt

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    Option 1 allows the Quantar to clock the data from the sub at the subs internal clock rate. Option 2 only forces the Quantar to clock from the network, you can't force the sub to clock at exactly the same rate as the network because when the sub transmits it only has its own clock to reference. The chance of slips is small given the elastic buffer in the Quantar and the reasonable precision of the sub clock. One part per million is not much at 9600 bps!
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    OK so I have it right then. I didn't realise the Quantar used elastic buffers but I guess info like that can only come from Motorolas engineers themselves - you must have some good contacts there

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    In my humble opinion the Quantar and the Astro Saber arguably tie for first place as the best Motorola has designed to date, despite their many flaws and quirks. Today's engineers have few excuses for poor work, with infinite memory and sophisticated RF design tools.
    It is a fine thing to be honest, but it is also very important to be right