Brocade 6910 Ethernet Access Switch Configuration Guide (Supporting R2.2.0.0) - Manual (Page 1038)

982 Brocade 6910 Ethernet Access Switch Configuration Guide
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Ethernet Ring Protection Switching
FIGURE 284 Showing Collected RMON Statistical Samples
Ethernet Ring Protection Switching
NOTE
Information in this section is based on ITU-T G.8032/Y.1344.
The ITU G.8032 recommendation specifies a protection switching mechanism and protocol for
Ethernet layer network rings. Ethernet rings can provide wide-area multipoint connectivity more
economically due to their reduced number of links. The mechanisms and protocol defined in
G.8032 achieve highly reliable and stable protection; and never form loops, which would fatally
affect network operation and service availability.
The G.8032 recommendation, also referred to as Ethernet Ring Protection Switching (ERPS), can
be used to increase the availability and robustness of Ethernet rings. An Ethernet ring built using
ERPS can provide resilience at a lower cost and than that provided by SONET or EAPS rings.
ERPS is more economical than EAPS in that only one physical link is required between each node in
the ring. However, since it can tolerate only one break in the ring, it is not as robust as EAPS. ERPS
supports up to 255 nodes in the ring structure. ERPS requires a higher convergence time when
more that 16 nodes are used, but should always run under than 500 ms.
Operational Concept
Loop avoidance in the ring is achieved by guaranteeing that, at any time, traffic may flow on all but
one of the ring links. This particular link is called the ring protection link (RPL), and under normal
conditions this link is blocked to traffic. One designated node, the RPL owner, is responsible for
blocking traffic over the RPL. When a ring failure occurs, the RPL owner is responsible for
unblocking the RPL, allowing this link to be used for traffic.