Fiber Automatic Transfer Switch

Mon Aug 17 19:53:51 UTC 2020

On 8/17/20 3:33 PM, William Herrin wrote:
> I want to dissuade you from using this architecture. When you have two
> paths, it's important to keep them both lit so that you can detect
> faults and correct them in a timely manner. The most intractable
> problem with active/failover architectures is that the failover proves
> inoperable when it's needed. The old backup tape that doesn't restore.
> Keep your layer-1's active all the time and do fault handling at a
> higher layer.

They have their uses - mostly protecting layer 1 products sold as such 
but also protecting things that can't be protected easily at higher 
levels such as RFoG.  However, if you're using them to sell protected 
layer 1 products (protected waves or OTN paths, basically), it's 
important to make sure you have at least some active traffic on the link 
at all times that can be monitored for exactly the reasons Bill alludes. 
  For a lot of networks, this can end up being just the OSC, but as 
that's often not subject to the full photonic path, I'd likewise advise 
against that being the case and to make sure you have at least some 
fully "in band" traffic that can be monitored along both legs.

-- 
Brandon Martin