Chapter 1 Introduction IPmux-16 Installation and Operation Manual
1-8 Functional Description
• Adaptive: In this mode, the E1 or T1 Tx clock is regenerated using the
Adaptive method. In this method, the fill level of the buffer receiving packets is
monitored. If the buffer begins to overfill, the regenerated clock frequency
increases to avoid overflow. If the buffer begins to empty, the clock decreases
to avoid underflow.
• Internal Clock: In this mode, the Transmit (Tx) clock is received from an
internal oscillator. This mode is useful for testing and diagnostic purposes.
Each of the clocks must be configured correctly on both the Receive and Transmit
ends to ensure proper operation and prevent pattern slips.
The following paragraphs describe typical timing schemes and their correct timing
mode settings in order to achieve end-to-end synchronization.
External Network Timing
When an external network is used to synchronize the E1/T1 devices, all the
IPmux-16 units should be configured to work in loopback mode (see the following
illustration). This topology enables any-to-any connectivity; as in the following
illustration, all three IPmux-16s have direct E1/T1 connectivity. In this timing
configuration both mesh and star bundle connection topologies are supported.
IP over
Ethernet
IPmux-16
E1/T1 Device
E1/T1
E1/T1
Clock from External Distribution Network
LBT Mode
IPmux-16 E1/T1 Device
E1/T1
E1/T1
LBT Mode
IPmux-16 E1/T1 Device
E1/T1
E1/T1
LBT Mode
Figure 1-6. IPmux-16 in Loopback Timing Mode
Single Source Clock Network
When a common clock is not available on all the ends of the network:
• E1/T1 Device Configuration:
One of the E1/T1 devices connected to the IPmux-16 should work as the
master clock while the others work in loopback timing.
• IPmux-16 Configuration:
The IPmux-16 E1/T1 ports connected to the master clock E1/T1 device work in
loopback timing, while the far-end IPmux-16s work in Adaptive mode.