Re: Question on HDLC and raw access to T1/E1 serial streams.
From: Ben Greear
Date: Sat Sep 30 2006 - 18:01:36 EST
Krzysztof Halasa wrote:
Ben Greear <greearb@xxxxxxxxxxxxxxx> writes:For protocols running HDLC as transport, I can just bridge HDLC frames.
I would want
I am looking for a way to bridge a T1/E1 network by reading a raw
bitstream from one T1 interface and writing it out to the other. The
application is adding delay and/or bit corruptions for impairment
I have been using Sangoma's drivers and NICs, but I'm having no luck
getting their latest stuff to work so I was hoping to use in-kernel
drivers (even if that means writing or hiring someone to write new ones.)
Is there currently a way to read/write the raw bitstream for a full T1
or E1 or a subset of channels?
Well, my generic HDLC works with HDLC framing only, T1/E1 is
a layer lower than that... I think Cyclades have (had?) a version
of PC300 card with T1/E1 interface. It at least doesn't require
any "binary blobs", though I think the driver would need some work.
Which line interface do you need? G.703?
Do you need to bridge multiple streams (not slots) over one
interface (internal (de)multiplexer - I mean "more than one
subset of channels")?
to be able to select the channel(s) for the HDLC frames.
For bridging something like voice, I think if I could break out an
individual channel into
a bit-stream interface, I could just read bits off on one T1 channel and
write to the other.
Preferably, I could also bond multiple channels (including an entire T1
or E1) and bridge
it as raw bits too.
I think if I could support these scenarios below, I would have
everything I need:
* Configure T1 as unchannelized bitstream, bridge entire thing to
* Configure channels 1-5 as a bitstream and bridge that to channels 1-5
of a second T1. (random proprietary bit-streaming protocol,
would probably bridge HDLC just fine, but handling
HDLC as frames would be more efficient I think.)
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)
* Configure entire T1 as HDLC transport, bridge HDLC frames from one T1
to the other.
Does that make sense?
Ben Greear <greearb@xxxxxxxxxxxxxxx>
Candela Technologies Inc http://www.candelatech.com
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