[c-nsp] Two DS3s Bounced at the Same Time

[Rodney Dunn]

All it takes is a switchover of some sort in the
transport path to send an alarm down the circuit
and the T3 will go down and come right back up within
a second or so.

If yours stayed down for longer than that then that
is not your problem.

There is no way to tell what went on for the circuit
unless you get some alarm history from the telco
gear.

The router (unfortunately) doesn't save it until you load
code where we added it.



On Sun, Mar 20, 2005 at 01:39:35PM -0700, John Neiberger wrote:
> > So, what sort of alarm are we talking about here? Is there some sort
> > of alarm that might clear up within two seconds, so the controller is
> > supposed to wait to see if the alarm is cleared before resetting
> > itself?
> 
> Following up on my own email, I just found this link that explains it
> a bit better:
> 
> http://www.cisco.com/en/US/products/hw/modules/ps2033/products_field_notice09186a00802ff01d.shtml
> 
> <snip>
> Problem Description
> 
>     The port adapters listed in the Products Affected section above,
> bring the T3 controller down immediately after receiving one of the
> following alarms on the wire: LOS or AIS.
> 
> Background
> 
>     Based on the ANSI T1.231 specification a T3 controller should not
> react to an alarm (LOF, LOS, AIS) unless the alarm persists for 2
> +/-0.5 seconds. The T3 Port Adapters (PAs) listed above in the
> Products Affected section do not adhere to the failure declaration
> specification threshold.
> 
> Problem Symptoms
> 
>     Since the T3 PAs listed above in the Products Affected section do
> not adhere to the two second holddown timer before reacting to an
> alarm as defined in the ANSI T1.231 specification, the controllers
> will go down immediately and come back up a few seconds later. This
> will result in loss of data and interference with user traffic.
> 
> </snip>
> 
> Now, if I could just figure out a way to determine if my equipment
> received an alarm at that time. It doesn't appear that I have an alarm
> history available.
> 
> Okay, I just ran into something even stranger. There are two PAs on
> the VIP in slot 12. I just tried "show controllers serial 12/1/0" and
> I got one page of data and then my SSH session was disconnected. I
> logged back in, tried a few other commands and then re-entered the
> "show controllers" command, and my session dropped again at exactly
> the same point. This really worries me.
> 
> John