[c-nsp] ATM-DXI on E1

[Gert Doering]

Hi,

a new challenge for us, but hopefully one of you has already mastered it :-)

We get a new leased line from one of our carriers, and for some weird
reason, als the "usual" stuff cannot be delivered - we have to take the
line as ATM encapsulation on E1 (ATM UBR, G.703/G.704, 30 timeslots).

My current plans are to get a Cisco 26xx with an NM-4E1-IMA or a
AIM-ATM + VWIC-1MFT-E1 combo, which should nicely support this
(the other end is delivered on an existing ATM-OC3 going into a 
7200 with PA-A3-OC3).

Now our carrier has declared "you can hook up a standard E1<->X.21
converter to that line, and use your normal X.21 routers", which *does*
surprise me.

I know that there is "ATM-DXI" encapsulation on Cisco serial interfaces,
but I have to admit that I'm not 100 per cent sure what it is - it's some
way to map ATM VCs onto a normal serial interface, but is it "just plain
ATM, all bits forwarded 1:1"?  Or is there some special processing going
on inside the ATM-E1 <-> ATM-DXI-on-X.21 converter?

>From reading http://www.cisco.com/warp/public/121/atmdxi.html, I understand
that the converter *does* need to do special processing, because the
SAR part of the ATM framing is done in the converter.  Correct?

Are there any off-the-shelf products out there that do ATM-E1 <-> X.21 DXI
that you can recommend?  I've seen E3 products (ADC Kentrox), but nothing
for E1.

thanks!

gert
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Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de