Specifications

Chapter 1 Introduction IPmux-11 Installation and Operation Manual
1-6 Functional Description
Testing
Diagnostic capabilities include E1/T1 local and remote loopback tests for rapid
localization of faults. The E1/T1 traffic can be looped locally, toward the line, or
toward the remote end (see Chapter 4 for more information).
Timing Modes
The E1/T1 Tx clock can operate in several timing modes to provide maximum
flexibility for connecting the IPmux-11 E1 or T1 channels.
Each of the clocks must be configured correctly on both the receive and transmit
ends to ensure proper operation and prevent pattern slips (see Figure 1-3,
Figure 1-4 and Figure 1-5).
The E1/T1 available Tx modes are:
• Loopback timing – the E1/T1 Tx clock is derived from the E1/T1 receive (Rx)
clock.
• Adaptive timing – 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 Tx clock frequency
increases to avoid overflow. If the buffer begins to empty, the Tx clock
frequency (toward the TDM device) decreases to avoid underflow.
• Internal timing – in this mode, the Tx clock is derived from an internal
oscillator.
• External timing – in this mode the Tx clock is derived from the external clock
input. The external clock port also outputs the input clock signal to allow
connection to other units, if needed.
In adaptive timing the regenerated clock is subject to network Packet Delay
Variation and may not comply with jitter and wander specifications.
Network Timing Schemes
The following paragraphs describe typical timing schemes and the correct timing
mode settings for achieving end-to-end synchronization.
External Network Timing
When the edges of the network are synchronized by an external network clock
source, all the IPmux-11 units should be configured to work in loopback timing
mode (see Figure 1-3). This topology enables any-to-any connectivity.
Note