[c-nsp] Line Code Violations

[Barton F. Bruce]

 > If you are doing DS-3 'clear channel'  (i.e. 45mbps) then you want it
> set for cbit.  If you are doing DS-3 'channelized' (i.e. 28 x DS-1
> circuits) then you want to use M13 (em-one-three, not em-thirteen)
> framing.  And yes, the framing should be the same for the entire
> circuit.
>

Sometimes using c-bit with multiplexed T1s on the T3 makes sense, and is
even necessary.

If you have a remote site that doesn't have ethernet handy, and the you need
to be able to reach into the little 1U M13 mux that is out there breaking
out 28 T1s (M13 literally means a Multiplexer from DS1 to DS3 - hence the
"em-one-three" naming previously discussed, also named like a 3-1 , or 1-0,
or even 3-1-0 DACs) and do it with no extra expense via the near end
matching M13 that packed the 28 T1s onto the T3 in the first place, you need
a cooperating matched same-brand pair. Both Telco Systems, and CAC units
work well with siblings but not with mixed brands. I assume Adtran will too,
but havn't tried.

The key is to have C-Bit turned on so there are available bits to do the end
to end transport of your telnet session. It is similar to the FDL bits you
get with ESF on a T1. I use /31s on the C-Bit link between Telco System
units and simply static route that net to the near end M13 that has the
local ethernet connection. It is not that they are "SMART" enough to know
that a /31 is really ok, but are actually dumb enough to not care. When you
telnet to its address, you are talking to the remote M13 over the C-Bit
link.

You can actually use that /31 TWICE for two seperate pairs of muxes. Just
flip which IP is used near and far for the 2nd pair, and static route just
the /32 address of the FAR unit to the near mux of each pair. Muxes only
talk to folks telnetting in or remote SNMP servers and don't need IP between
different pairs, so noone is confused or even notices.

You can load new microcode, and do most anything you can do on the local mux
to the remote one EXCEPT looping the T3, which would be suicide.

Also, even different brands of M13s support remote looping any ONE or ALL
T1s at the far mux and then you can have the near mux BERT through the
loopback or whatever. But unless C-BIT is on, you can't have a selection of
random T1s looped at the same time and each loop taken up/down individually
at will. With C-Bit on, you get a lot more flexibility. This is just mux to
mux, I'm not talking about other equipment passing loop up/down signals
either inband or via T1 FDL signalling that simply passes through the M13s.

If you are coming out of a PA-MC-2T3+ and feeding into a VZ "CO hub/muxing"
service to save big $s on near end local loop charges, you need to see what
they will let you configure.