[30287] in North American Network Operators' Group
Re: Sonet protection usage
daemon@ATHENA.MIT.EDU (Danny McPherson)
Wed Jul 26 00:36:12 2000
Message-Id: <200007260435.WAA15440@tcb.net>
To: nanog@merit.edu
From: Danny McPherson <danny@tcb.net>
Reply-To: danny@tcb.net
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Date: Tue, 25 Jul 2000 22:35:04 -0600
Errors-To: owner-nanog-outgoing@merit.edu
> Think about it -- are they really provisioning two circuits, leaving
> one available as a backup? Of course not!
I think you missed on of my points, which was APS on the trib side of the ADM,
only a small mention of APS on the network side. If you can't figure out
whether you've two circuits sitting there you've got bigger problems...
> This may be a useful feature for voice circuits, where most of the
> capacity sits idle most of the time. It's worse than useless for data.
Again, I think you're missing the application wrt it residing on the trib side
of the ADM -- to protect against router failures -- continuing to use the same
network portion (i.e. the expensive portion) of the connection.
> APS was designed to protect against the failure of the electronics
> for a single fiber in a cable. Often, a dozen other circuits are
> "protected" by a single APS. It's a ripoff.
Perhaps in your experience, though I can argue quite the contrary, especially
when your company owns the the transmission facilities. Though again, I was
referring primarily to local protection against router failure on the trib
side of the ADM.
> Of course, the usual failure mode is backhoe fade, not electronics.
> In which case, that APS circuit was cut along with the rest.
Of course, backhoes don't normally work inside PoPs, which is the application
of APS I was referring to. Routers do fail though (often more than links),
and APS has been demonstrated to work relatively well for protecting against
such failures.
> For transoceanic links, diverse APS is even more unlikely, and unless
> you are paying serious money, you won't be a priority over the other
> hundred customers that are sharing that APS circuit.
Not on the trib side, when protecting against router failures.
> Diverse links _are_ the only _real_ protection. You might even get
> what you pay for.... And in the short term, you at least get twice
> the bandwidth
Again, APS w/two local links to an ADM sufficiently protect against a local
router failure.
-danny
