Ascend Archive
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Re: (ASCEND) Max-4000 E1/T1

On Mon, Apr 20, 1998 at 08:42:31AM +0200, Mickey Coggins wrote:
> > E1 is a much cleaner design compared to T1. While T1 uses some esoteric
> ...
> > It's obviously been designed after some years of observation of T1 and
> > made better ;)
>  
> While these things are true, one thing the E1 spec seems to have left off
> is the ability to quiese a PRI!

If you by "quiese" mean to signal to the telco that an E1 is currently
inoperative and the telco should refuse calls which otherwise would
be routed to this PRI (or route them to another PRI if the failed one
is part of a "bundle"), I would see at least two ways to do that:

1) Signal L1 loss. The E1 can do that, see G.704 and the RAI (Remote Alarm
   Indication) bit in TimeSlot 0. I'm pretty sure the telco will notice
   when we would send RAI and would itself go to AIS until we clear the
   situation. Just going to send AIS would be as effective, IMHO.

2) Drive down L2. As long as L2 is not in sync (after a SABME) the telco
   should not count the PRI as operative. I dunno whether it is easy to
   cleanly shut down L2 so the telco notices, but I expect that there
   is one way or another.

> It would be really cool if Ascend could somehow trick the switch into
> thinking that all lines are in use, as a workaround for this omission.

This is, AFAIK, impossible. The switch is the final location where state
is kept of which Bs are allocated and which are not. I don't expect that
there would be a way to trick this. Actually signalling L2 or L1 down is
the clean way. The big question is whether the telco interprets this in
the correct way (switches are computers running software, too...).

-- 

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