Upstream and Downstream

The terms upstream and downstream are used in defining SONET alarms and errors. The terms are meaningful when viewed from the point of view of the failure in the circuit.

For example, in Figure 12 the failure occurs in the section between ADM1 and ADM2. The signal is transmitted from Router2 in the direction of Router1(from right to left). In this example, Router1, Repeater1, and ADM1 are downstream from the failure. ADM2, Repeater2, and Router2 are upstream from the failure.

Figure 12: Example of an Upstream or Downstream Failure

The failure sends an alarm from ADM1 to Router1 in the direction of the signal transmission (downstream). Alarms are also sent from ADM1 to ADM2 and from Router1 to Router2 in the opposite direction of the signal transmission (upstream).

In Figure 13, the failure is also between ADM1 and ADM2. However, the signal is transmitted from Router1 in the direction of Router2 (from left to right). Router2, Repeater2, and ADM2 are downstream from the failure. ADM1, Repeater1, and Router1 are upstream from the failure.

Figure 13: Another Example of an Upstream or Downstream Failure

This failure sends an alarm from ADM2 to Router2 in the direction of the signal transmission (downstream). Alarms are also sent from ADM2 to ADM1 and from Router2 to Router1 in the opposite direction of the signal transmission (upstream).

All diagnostics are from the perspective of the PTE (the Juniper Networks router). Although the exact source of the problem can be difficult to find without having access to the LTE or the STE, you can at least determine from the PTE output whether the problem is remote or local.