H3C Technologies H3C SR8800 - Manual (Page 29)

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Figure 3 Ring structure of RPR
Ringlet 0, also called the “outer ring,” is for clockwise or west data traffic. Ringlet 1, also called the “inner
ring,” is for counterclockwise or east data traffic.
On Ringlet 0, stations send data frames out of east ports and receive data frames from west ports. On
Ringlet 1, stations send data frames out of west ports and receive data frames from east ports.
Any two adjacent stations are connected by a pair of unidirectional logical channels called “links”
transmitting in opposite directions. These two links form a span. Multiple continuous spans and their
stations form a domain. A span on which data frames are not allowed to pass is called an “edge.” If a
ring contains at least one detected edge, it is called “open ring.” If it does not contain any detected
edges, it is called “closed ring.”
Data operations on RPR
Stations on an RPR handle data frames by performing the following four types of operations:
• Insert, to place a frame on a ringlet.
• Transit, to pass a frame to the next station.
• Copy, to deliver an inbound frame from the ring to the upper layer. Copying a frame does not
remove the frame from the ring.
• Strip, to remove a frame from a ringlet. The frame is not passed to the next station.
By performing these operations, stations implement unicast, broadcast, multicast, and unknown unicast
transmission.
Station
Ringlet 1
Ringlet 0
Link
Span
Domain
East port
West port