Telco Intrusive T1 line test to Smartjack or router WIC/Controller module

[will]

I'm trying to get more info on how & what the telco actually tests when you ask them to perform an intrusive T1 line test. Previously, i thought they test by creating a loop in their smartjack in our Demarc. If it tested good, then the cable from the smartjack to my router at the site still might be questionable.

Recently, i had a telco engineer tell me, that they can send a signal to my router WIC module (to the router's actual controller card), which will put my router WIC into loopback. And then the intrusive test runs from the CO all the way to my router interface.

Which one of these is true? We are up in the pacific northwest dealing with Century Link, with a typical smartjack, as you might see in a 2-4 port NIU module mounted in the demarc. Line is copper from the CO.

Thx in advance, Will

[Leo Laohoo]

Both true but there's a logic behind this madness. 

The old traditional way, when I used to work for SITA/Equant, was the telco can run a loop test in any path and in any exchange up to the demarc.  The reason why it's "up to the demarc" because they don't want to be held responsible for the cabling from the demarc up to the NTD/NTU particularly when they're not the one who "authorize" this.  

But back when I was working for SITA/Equant, we always run the loop test in conjunction with the telco.  Reason:  Because I have learnt never to trust what they say.  I have been in so many situation where the telco tells me "loop is good, we see return packets".  The minute I run the loop test on the Nortel DPN 100 or Passport switches, I can verify if the telco are telling the truth or not.  Most of the time, and I mean above 80%, their software-driven loop test lies or is very inaccurate.  This happens to all the telco I had to deal with, US, Australia, UK, etc.  

[will]

thx leo, I'm still a little baffled. I originally asked the Telco if I could do what I think you are saying. I was going to loop my serial interface in the router and have Telco test all the way to the router. my thought was I could rule out local post-demark cabling that I may have installed incorrectly or needs replacing.

When I posed this, the Telco said they already tell my router's wic to go into loopback from some code, which they can issue from the CO. This sounded to me like they were talking about putting their Smartjack into loopback, not my routers serial interface.

So can they remotely tell my router's interface to loop itself? almost doesn't make sense to me, and they shouldn't be able to control that. So I'm not really buying this at the moment - until someone tells me otherwise.

[Leo Laohoo]

Serial interface?  Yes they can, however, the TELCO runs the loopback and send packets from their side and (hope to) see the return packets on their side.  YOU don't see or even get the opportunity to verify if their looptest.  If the Telco says looptest were fine then you'll have to take their word for it.  

Unlike my case, I get to send packets and see if there were packets returned and how many came back.  

[will]

thx leo for you second reply. i guess that means teclo can test all the way to my routers serial interface. interesting!

[Leo Laohoo]

Yes they can but how can you verify?  That's the beauty of doing loopback test is for the user to verify by doing your own independent test.