System information

FCD 901 48

Issue R2A, 07.2009

XMP1 Release 5.5 System Description

Configuring a clock tree with preferred priority

Page 2-22 Proprietary Information Aastra

2.3.6.7 Configuring a clock tree with preferred priority

Preferred port for priority 1

To switch off the automatic clock tree assignment function, it is possible to

define a preferred port in XMP1 nodes.

In order to ensure that a fixed path is observed for setting up the clock tree

in a fully operational network, any port can be selected and configured as

preferred port for priority 1.

In this case, only Y5-bit evaluation at the preferred port is used in this node

for clock control. The Y5-bits of all other ports in the node are no longer

taken into consideration.

In the root node of the clock tree, clock priority 1 is therefore selected from

the clock priority list to achieve a secure clock such as the T3in clock.

In all other nodes of the clock tree, the ports used as preferred ports for

clock priority 1 are configured via info no. 12 of the decentral card slot data.

Simultaneously, clock priority 2 must be reserved. When making the

configuration using SOX, clock priority 2 is simply not assigned in the entire

network. See Fig. 2.8.

In the example shown below, node 1 is the clock master with priority 1 for

T3in. The Tint clock in node 3 is assigned clock priority 2.

Figure 2.8: Clock transmission with preferred clock priority 1: normal oper-

ation

Loss of signal at a preferred port

If the 2 Mbit/s signal fails at the preferred port 1 of node 2, the Y5-bit

available at port P3 will be evaluated in node 3. Since clock priority 1 is also

being received at this port, clock priority 1 is still valid for node 3. Since,

however, clock priority 1 is now evaluated at a port not defined as preferred

port, not clock priority 1 is passed on, but the reserved clock priority 2 is

injected. This indicates that the clock is currently not spreaded in the

defined preferred clock tree. See Fig. 2.9.

Node

T3in=Priority 1

P1 P1 P3

Tint=Prio.2

TP1

TP1TP1

"1"

Node 2:

Port: dec. info no. 12 = yes

Node 3:

Port: dec. info no. = yes