Installation and User Manual
EtherHaul
1200™
Page 114
EH-INST-02, Issue 4.0
7.5
Configuring Ethernet Ring Protection (ERP)
Ethernet Ring Protection (ERP) is a network resiliency protocol defined in ITU-T G.8032.
The EtherHaul 1200 supports ERP G.8032v2, with backwards compatibility to previous
versions. ERP support enables protection for any point of failure in the network. This
means that network connectivity is maintained in the event that the Ethernet link, the
radio link, or even the entire EtherHaul 1200 fails. This provides resiliency for both
Ethernet-Ethernet rings that typically protect single site connectivity and Ethernet-RF
rings that typically protect against RF network failure.
ERP is a relatively simple protocol that operates at the network level on the set of nodes
that constitute the ring or set of rings. ERP monitors the Ethernet layer to discover and
identify Signal Failure (SF) conditions, and prevents loops within the ring by blocking
one of the links (either a pre-determined link or a failed link). ERP verifies at all times
the ring is closed that frames will not be looped. This is accomplished by taking down a
Ring protection Link (RPL) whenever there is no failure in the ring.
Using ERP, EtherHaul 1200 provides protection and recovery switching within 50 ms for
typical rings. The ERP mechanism uses a very small percentage of total available
bandwidth.
Figure
7-20
illustrates the basic ERP protection mechanism. In normal ring operation,
the RPL is blocked. In a failure condition, the failed link is blocked, R-APS messages are
sent from the nodes adjacent to the failed links in order to unblock the RPL, and an FD B
flush is performed on all ring nodes as necessary.
Figure
7-20 Basic ERP Protection Mechanism
7.5.1
Supported ERP Features
Among the ERP features supported by the EtherHaul 12000 are:
Backwards compatibility to previous versions
Revertive and non-revertive behavior
Flush logic with the Node-ID and BPR (Blocked Port Reference) mechanism
Administrative commands (manual and forced switch, clear)