3Com S7902E, Configuration Manual

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for example, when a trunk fiber is broken or an OLT port becomes abnormal, a switchover is performed
automatically between the two OLTs, which act as backup for each other. You can also perform a
manual switchover between two OLT ports added to the backup group as needed.
Figure 1-5 depicts a
fiber backup group, where POS is a 2:N optical splitter.
Figure 1-5
Network diagram for a fiber backup group
S7900E Series Switches and EPON System
Features of an S7900E Switch Working as an OLT Device
With an EPON card installed, an S7900E switch can work as an OLT device in an EPON system. In
such a case, the S7900E switch has the following features:
Compliance with EPON interoperation standards: Interoperable with other vendors' ONUs that
support
China Telecom Technical Requirements for EPON Devices
.
Integrating access and convergence: Each EPON card in an S7900E switch has multiple physical
OLT ports, and each OLT port has 64 logical ports, namely, ONU ports, each of which can
correspond with an ONU. Thus, one EPON card can work as multiple OLT devices. This reduces
users' equipment purchase costs, and the management costs and fault ratio caused by
interconnection between multiple device ports.
Powerful ONU remote management capabilities: You can centrally manage and configure different
services on ONUs and ONU UNI (User Network Interface) ports through OLTs. This greatly lowers
subsequent maintenance costs.
Excellent security protection: OLTs can protect network devices in terms of control, management,
and forwarding against illegal access or abnormal traffic.
Powerful access control list (ACL) and QoS functions: OLTs support standard and extended ACLs,
and support traffic policing, traffic shaping, packet priority, multiple queue scheduling mechanisms,
multiple congestion avoidance mechanisms, and other QoS assurance functions.
Three Port Types in an EPON System
When an S7900E switch works as an OLT device in an EPON system, the EPON system has three port
types: OLT, ONU, and UNI, as shown in
Figure 1-6 .