Chapter 3 Interfaces and Communications
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FIGURE 18 − SPATIAL REUSE
As shown in
Figure 18, Node 1 in the outer ring sends the
service to Node 4. Node 2 sends the service to Node 3. Node
5 sends the service to Node 6. With the spatial reuse
technology, the unicast service from Node 5 to Node 6 is able
to occupy the whole space. The service from Node 1 to Node
4 only occupies the bandwidth from Node 2 to Node 3.
Bandwidth control
The bandwidth-control algorithm dynamically negotiates
available bandwidth between the nodes on the ring. This
applies only to the low-priority service. It ensures that nodes
will not be disadvantaged because of ring location or
changing traffic patterns. The algorithm only manages
congestion, enabling nodes to maximize the use of any spare
capacity. Nodes can be inserted or removed from the ring
without any bandwidth provisioning by the host.
Fair bandwidth
The RPR is a sharing ring. It needs an access control
mechanism to ensure fair bandwidth and control latency. The
access control mechanism contains the global access control
and local access control.
f Global access control: Control all nodes to obtain a fair
bandwidth globally.
f Local access control: Control one span in the ring to
optimize the bandwidth.
Physical layer
The RPR specifies the MAC standard and interface
specifications from MAC to PHY, including PLCP. RPR packets
can be transported over both SDH/SONET and Ethernet
physical layers.
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