Editing Synchronous optical networking (section)

===Timing loops===
A timing loop occurs when network elements in a network are each deriving their timing from other network elements, without any of them being a "master" timing source. This network loop will eventually see its own timing "float away" from any external networks, causing mysterious bit errors—and ultimately, in the worst cases, massive loss of traffic. The source of these kinds of errors can be hard to diagnose.<ref>{{cite book |chapter-url=http://www.cisco.com/en/US/tech/tk482/tk607/technologies_q_and_a_item09186a008016c442.shtml#qa10 |chapter=Why is a timing loop so bad, and why is it so difficult to fix? |title=Optical Timing: Frequently Asked Questions |publisher=[[Cisco Systems]]|date=2 December 2005 |access-date=28 September 2012}}</ref> In general, a network that has been properly configured should never find itself in a timing loop, but some classes of silent failures could nevertheless cause this issue.