User's Manual

Table Of Contents
22 2. System Description
Connected to
east modem
Connected to
west modem
Connected to
east modem
Connected to
west modem
Connected to
west modem
Connected to
east modem
Connected to
west modem
Connected to
east modem
Figure 2-8. 2 + 0 (East West) Configuration
2.8Spanning Tree Protocol (STP)
Spanning Tree Protocol (STP) keeps Ethernet loops from forming in a ring architecture.
Without STP, loops would flood a network with packets. STP prevents loops by creating
an artificial network break. In the event of a network outage, STP automatically removes
the artificial break, restoring connectivity.
2.91+1 Protection
The Event HD supports 1+1 protection as an option for a critical link. In this
configuration, protection is provided in a single 1 RU chassis. The SDIDUTM contains two
power supplies and two modems. The power supply, ODU, IF/telemetry and modem are
protected. The digital framing and LIUs are not. One modem is referred to as the west
modem and the other as the east modem. 1+1 protection can be run in two modes called
Protected Non-Diversity and Protected Diversity.
2.9.1Protected Non-Diversity (Hot Standby)
Figure 2-9 shows operation in Protected Non-Diversity mode, also called Hot Standby. In
this mode, one ODU at each location transmits to two ODUs at the other location. This
© 2007 Moseley, Inc. All Rights Reserved. 602-14886-01, Rev. A