OptiX OSN 7500
Technical Manual - System Description
6 Data Features
Huawei Technologies Proprietary
6-9
2.
RSTP
The Ethernet boards support spanning tree protocol (STP) and rapid spanning tree
protocol (RSTP). When STP is started, modify the logic network topology to avoid
potential broadcast storm.
3.
Flow Control
The Ethernet interface supports IEEE 802.3X flow control, minimizing the packet loss
caused by congestion. As shown in Figure 6-8, the node connecting with Ethernet in
duplex mode sends PAUSE frame to ask the receiving node to stop transmitting frame
signals within a pause-time (N seconds), so as to avoid frame loss.
Duplex
Buffer is not full.
Pause frame
Pause-time = N seconds
Pause frame
Pause-time = 0 second
Data transmission
Ethernet switch
Ethernet switch
MSTP
Data transmission
Data transmission
Buffer is not full.
Buffer is not full.
Buffer is full.
Buffer is full.
Figure 6-8
Flow control at the Ethernet side
6.2
RPR Features
This section introduces the RPR features of the OptiX OSN 7500 in terms of function,
application and protection.
6.2.1 Function
The EMR0 and EGR2 boards of the OptiX OSN 7500 supports resilient packet ring
(RPR) features defined by IEEE 802.17. RPR employs a dual-ring structure utilizing a
pair of unidirectional counter-rotating rings, as shown in Figure 6-9. Both the outer ring
and the inner ring bear data packets and control packets, featuring high bandwidth
utilization. The control packets on the inner ring carry control information for the data
packets on the outer ring, and the control packets on the outer ring carry control
information for the data packets on the inner ring. The two rings act as backup and
