Re: Sonet protection usage

["Bora Akyol" <akyol () akyol org>]

Note that I am not a big fan of APS, but:


----- Original Message -----
From: "William Allen Simpson" <wsimpson () greendragon com>
To: <danny () tcb net>
Cc: "Steve Feldman" <feldman () twincreeks net>; <nanog () merit edu>
Sent: Tuesday, July 25, 2000 9:04 PM
Subject: Re: Sonet protection usage


> Think about it -- are they really provisioning two circuits, leaving
> one available as a backup?  Of course not!
>
> 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.

APS can be useful for data as well.

> 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.

I think this is a huge oversimplification of APS and how it works. Yes APS
allows the
**operator** to backup various primaries to a backup. It allows 1:1 which is
same as diverse
circuits. This is the case of a rope that is **long enough**.

> Of course, the usual failure mode is backhoe fade, not electronics.
> In which case, that APS circuit was cut along with the rest.

If you run your APS primary and backup on the same conduit then APS can not
undo bad
network design.

> 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.

Well-engineered trans-oceanic links are laid such that there are at least
two conduits running parallel
some large distance apart.

> 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.

Or you can run 1+1 IP Bonded interfaces and achieve the same effect ;-)

> WSimpson () UMich edu
>     Key fingerprint =  17 40 5E 67 15 6F 31 26  DD 0D B9 9B 6A 15 2C 32