LevelOne GTL-2691 - Manual (Page 464)

C HAPTER 14 | Basic Administration Protocols
Ethernet Ring Protection Switching
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Figure 257: Showing Collected RMON Statistical Samples
E THERNET R ING P ROTECTION S WITCHING
N OTE :
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