Cabletron Systems 04-0053-01 manual Network Clocking

Port Clock Configuration ATM Filtering and Clocking

By default, the clock mode for all SmartSwitch 6500 ports is local. Use the set portclockmode command to change a ports clocking source. For example, the following sets port 5a3 into loopback mode.

SmartSwitch	# set portclockmode
PortNumber(ALL)		: 5a3
PortClkMode(local)		: loop
SmartSwitch	#

Note Never configure two connecting port to both be in loopback mode. Without at least one of the connecting ports generating a clocking signal, connectivity will go out of sync and communication will be lost.

8.2.1Network Clocking

Network clocking allows your SmartSwitch 6500 to obtain an external, high-quality, precise clocking signal and make it available for use by all ports. Typically, network clocking is configured when a high-quality clock signal is available (for example from a service provider connection) and the SmartSwitch is supporting traffic from applications that are time-sensitive, such as voice and video. The port connected to the high-precision clock signal is specified as the network source using the set networkclock command. When set, the port is essentially placed in loopback mode, however, the port also places the incoming, high-precision signal on the SmartSwitch 6500’s backplane, where it becomes available to all other ports.

The following is an example of network clocking configuration. It is assumed in this example that the SmartSwitch 6500 is connected through port 7a1 to a service provider’s switch that produces a high-precision clocking signal.

1.Use the set networkclock command to specify the port through which the network clocking signal is to be obtained

SmartSwitch # set networkclock

PortNumber(none) : 7a1

SmartSwitch #

2.Use the set portclockmode command to instruct ports (either all ports or on a per-port basis) to use the clocking signal obtained from port 7a1

SmartSwitch # set portclockmode
PortNumber(ALL)	: — In this example, we set all ports to use the network clock
PortClkMode(local)	: network

SmartSwitch #

Once the set portclockmode command is entered with the PortClkMode parameter set to network, the ports specified on the SmartSwitch 6500 now use the clocking signal received on port 7a1 as their port clock source.

8-4 SmartSwitch ATM User Guide