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Frequently Asked Questions

Q1

Does a ring require an EXNET® Ring Master?

A1

Yes, every ring must be assigned an EXNET® Ring Master

Q2

Why does the ring require an EXNET® Ring Master?

A2

EXNET® Ring Master nodes drive the timing for the packets on
the ring.

Q3

How do you find out which CSP node is the EXNET® Ring
Master?

A3

Use the Ring Status Query message to identify which CSP node is the EXNET® Ring Master.

Q4

How is the EXNET® Ring Master determined?

A4

During ring initialization, the CSP nodes arbitrate to determine which becomes the EXNET® Ring Master.

Q5

Can an CSP node be Master of more than one EXNET® Ring?

A5

Yes. The default setting is for a node to be Master of only one EXNET® Ring, but the CSP Ring Timing Enhancement allows you to change this default.

Q6

Is there a relationship between the number of rings and the number of CSP nodes in an CSP network?

A6

There is no defined relationship. In a network there can be fewer rings than nodes, more rings than nodes, or the same number of rings as nodes.

Q7

What happens when the CSP node that provides the ring timing fails, and another CSP node on the ring has been configured to be master-configurable?

A7

The ring goes down and all master-configurable nodes arbitrate to become EXNET® Ring Master.

Q8

What happens when the CSP node providing the ring timing fails, and there IS NOT another CSP node on the ring that has been configured as an EXNET® Ring Master?

A8

The ring goes down and remains down until a master-configurable CSP node becomes available.

Q9

What API messages support the changes required for the CSP Ring Timing Enhancement?

A9

The following API messages support the changes: EXNET Ring Configure (0x74), Ring Status Query (0x71), Ring Status Report (0x72), EXS Node Configure (0x7F), EXS Node Configuration Query (0x7E), Loop Timing Configure (0x4A).

Q10

When should I configure an CSP node to be non-master configurable?

A10

When it or its timing source is considered too unreliable to drive the timing for the EXNET® Ring (for example, nodes with a free running clock, with loop timing from a non-network connected source, nodes frequently taken out of service, nodes not configured for redundancy).

Q11

Should I make all CSP nodes non-master-configurable except for the CSP node I want to become the EXNET® Ring Master?

A11

You should designate all CSP nodes with a quality clock source as master-configurable.

Q12

What happens if none of my active CSP nodes are master-configurable?

A12

No CSP nodes arbitrate to become EXNET® Ring Master, and the ring will not come up.

Q13

Why not configure one CSP node to derive its timing from the PSTN and have all other CSP nodes on that EXNET® Ring derive their timing from the ring?

A13

To ensure accurate synchronization, all CSP nodes connected to the PSTN should derive their timing from the PSTN. While deriving timing from the ring is superior to free-running, the less equipment between the original timing source and the CSP node, the better the synchronization.

Q14

Why not permit all CSP nodes on redundant EXNET® Rings to become EXNET® Ring Masters on both rings?

A14

Loss of an EXNET® Ring Master brings the ring down. If a Master of multiple EXNET® Rings comes out of service for any reason, all rings go down for which the node is Master.

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