Telco discussions

Rob Gutierrez rmg at
Wed Jun 26 23:00:38 UTC 1996

> >This is because most vendors still believes that T1 circuits are provision
> >as D4/AMI..:-) Digital Link Encore csu/dsu by default has it setup as 
> >ESF/B8ZS.
> I'm evaluating the new cisco 2524 with internal CSU/DSU, and it looks
> like the default is ESF/B8ZS on this box too.  Maybe there's hope for
> the vendors catching up with reality on this front afterall.

I haven't touched a 2524 yet.  Is the DSU options set on the command line?

> Anyone have experience mixing different vendor CSU/DSUs and getting
> things like remote loopback to work?

In-band and out-of-band lookpback codes should work fine.  The differences
I've seen are with in-band codes.  Some CSUs need to see the loop-up
code unframed, and some will respond to the loop-up code framed.

Rememeber that you can't send an out-of-band loop-up code unless
(a) you're ESF framed, and (b) the CSU is optioned to acknowledge
any o-o-b request.

An Out-Of-Band code is also known as an ESF code.  The loop-up or loop-
down requests are sent in the 4kbps ESF channel instead of the actual data

Also remember that CSU and NIU (Network Interface Units) codes are
different.  Make sure you're sending a CSU code.  An NIU code is
technically called a Facility-2 code (FAC-2).

Since one mfgr's unit can't be configured to send a framed or unframed
loop-up/down (it doesn't tell you), you're at their mercy.  Same if you
want to send an in-band or out-of-band code.

With a test set, though, I've never run across a CSU or NIU that I couldn't
loop up or down.  You can virtually set a test set to do _anything_.


p.s...I have the data sheet scanned in.  I'm gonna html it.

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