ADTRAN 4200659L8, 4200659L1, 4175043L2, 4200659L5, 4200659L2, 4200659L7, 4200659L3 Unit Timing, Snmp

Chapter 1. Introduction

Unit Timing

The MX2800 STS-1 multiplexer allows three timing methods. The first is LOOP timed, in which the multiplexer derives timing from the incoming STS-1 signal. A failure in this signal, such as a loss- of-signal (LOS) or a loss-of-framing (LOF) will cause the unit to enter HOLDOVER (HO) mode for the duration of the receive signal defect. During HO, the unit will continue transmitting at the same rate as the receive signal prior to entering its defect condition. Stability of the transmit during HO is guaranteed to +/- 4.9 ppm over 24 hours. The defect condition must be cleared before LOOP time mode can be resumed.

The second mode of operation is FREE-RUNNING(FR) mode. In this mode, an internal oscillator is used to generate transmit timing. FREE-RUNNINGmode provides a SONET minimum clock specification of +/- 20 ppm.

The third timing operation mode is EXTERNAL. EXTERNAL timing mode allows the MX2800 STS-1 to derive its transmit timing from any one of the 28 DSX-1/E1 physical ports. The ports selected may be data carrying ports. Two sources can be specified to provide external timing: a primary and a secondary source. Failure of the primary source (due to LOS or AIS) will cause the unit to switch to the secondary source, if available. In the event that both the primary and secondary sources are lost, the unit will enter HOLDOVER mode as described previously. Holdover mode will be exited upon recovery of at least one clock source.

SNMP

The MX2800 STS-1's embedded SNMP feature allows the unit to be accessed and controlled by a network manager through the 10BaseT local area network (LAN) port. The MX2800 STS-1

61200659L1-1 MX2800 STS-1 User Manual 1-5