[Asterisk-Dev] Raw E1 capture

[Mike M]

On Wed, Jul 27, 2005 at 05:56:55PM +0200, Peter Svensson wrote:
> On Wed, 27 Jul 2005, Michael Beukman wrote:
> 
> > I would like to use the card to capture the Raw E1 stream to my HDD.  We
> > have
> > developed some applications what will do protocol analyses on various types
> > of E1 streams; standard interfaces as well as some propriety interfaces.
> > 
> > So its very important that I capture the E1 raw.
> > 
> > Is this possible, and could you point me in the right direction?
> 
> I think it may be hard to do with a hardware channelized E1 card such as 
> the Digium TE110P. You may have better luck with a Sangoma A101u or 
> similar card (http://www.sangoma.com/products/p_aft-et1-specs.htm).

The Sangoma card will deliver a raw bitstream minus the framing bits.
For T1 you can receive 192 bits per frame (24 slots). The 193rd
bit is not available. For E1 you can receive 31 of 32 slots.  I can't
remember if the framing slot is 0 or 31, but it doesn't matter because
you can't see it.  A user defined number of frames per packet are delivered 
to user level socket interface. 

Bits are stored in octets in order of receipt from LSb to MSb.

The raw bitstream delivered is appropriate for protocol analysis. You
will need to have your own HDLC receiver.

You need 2 ports to monitor a single T1/E1.  You actually need 2
receivers.  You will need to use the A102.  You'll need to fashion a tap
cable. Google on "sangoma tap monitor" for for detail.

There are cards available that deliver the full bitstream but they are
harder to work with since you'll have to find the frame boundrys on your
own.

-- 
Mike