[nsp] clock extraction

[Kostas Anagnopoulos]

Hi all,

In http://www.cisco.com/warp/public/74/154.html cisco
makes a distinction between clocked and unclocked circuits.

The question i have is,what's the difference between a clocked and an
unclocked circuit.
My understanding is that timing is not carried separately from the data
stream.
Consequently network elements derive clock from the incoming bitstream.
If this is the case,how the network elements detect the absence or existence
of clock in a circuit.

Thank you for your help,

Kostas