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    SubjectRe: Question on HDLC and raw access to T1/E1 serial streams.
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    Ben Greear <greearb@candelatech.com> writes:

    > I think if I could support these scenarios below, I would have
    > everything I need:
    >
    > * Configure T1 as unchannelized bitstream, bridge entire thing to
    > second T1.

    I think it should be easy with such card, though I think the drivers
    can't currently do that.

    > * Configure channels 1-5 as a bitstream and bridge that to channels
    > 1-5
    > of a second T1. (random proprietary bit-streaming protocol,

    I think the hardware would permit that. Probably needs additional
    driver support and I'm not sure about timeslot synchronization (for
    HDLC, sync doesn't matter).

    > would probably bridge HDLC just fine, but handling
    > HDLC as frames would be more efficient I think.)

    Not sure, maybe yes (less data to bridge due to bit stuffing, flags etc.),
    maybe not (variable length of HDLC frame).

    > channels 6-10 configured as an HDLC interface, bridged as HDLC
    > frames to channels 6-10 of a second T1. (PPP & other protocols over
    > HDLC)
    > channels 10-24 each configured as a separate bit-stream, bridged to
    > channels 10-24 on the second T1. (Voice)

    I think the above could be a problem - I think common T1/E1 cards
    can do only one stream at once.

    I wonder if it can be done in software - the hardware framer would
    have to pass all data transparently, and it would be demultiplexed,
    processed and then multiplexed by the driver. Quite complicated,
    but I think at 2 Mbps it wouldn't be a CPU performance problem.

    > * Configure entire T1 as HDLC transport, bridge HDLC frames from one
    > T1 to the other.

    Easy even with existing drivers I think (no bridge support but it's
    trivial).
    --
    Krzysztof Halasa
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