Peavey MediaMatrix NION Hardware Manual page 60

Chapter 6 - Using XDAB clusters with VLANs and CobraNet
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Worked example 2 - a bad configuration
The Conductor for VLAN 1 is the second device in the VLAN 1 segment within XDAB
Cluster 1. It is therefore the clock source for VLAN 1 (clock path 1).
The XDAB master in Cluster 1 is therefore a CobraNet performer in VLAN 1.
The audio clock will originate in the Conductor from which the XDAB master (a
performer) will get its clock via CobraNet.
The performer, XDAB master, will then supply its clock to the XDAB chain (clock path 2)
from which the Conductor will get its clock.
A clock loop exists in this example.
The XDAB master is relying on the CobraNet Conductor for its clock source, delivered to
it via CobraNet., but the CobraNet Conductor is relying on the XDAB master for its clock
source delivered to it via XDAB.
Both devices consider the other one to be their clock source and so neither can provide a
stable clock to the other.
Clock Path 1 is a CobraNet clock distributed on the network and is an unstable clock for
reasons outlined above. Therefore, the audio clock in cluster 2, which is received on clock
path 1 and propagated via XDAB to the other devices in the cluster, will also be unstable.
No device in Cluster 1 or Cluster 2 will have a stable audio clock.
Note: It may be possible for the two clocks (XDAB master and Conductor in cluster 1) to
become stable and synchronous. But this will be a time consuming matter of chance, rather
than a deterministic certainty, as the XDAB chain attempts to arbitrate a master. In the
absence of any beneficial timing coincidences at the beginning of a sync attempt, the
clocks would never sync up.
56 Version 1.6.1.0 September 30, 2010