Ethernet ring protection (ERP) defined by G.8032 has been developed on a principle of utilizing generic mechanisms inherited from the traditional Ethernet MAC and bridge functions. The objective of fast protection switching is achieved by integrating mature Ethernet operations, administration, and maintenance (OAM) functions and a simple automatic protection switching (APS) protocol for Ethernet
ring networks. In addition, since ERP is based on standard Ethernet, it can take advantage of the rapidly increasing Ethernet bandwidth-cost merits with 1GbE, 10GbE, 100GbE, etc., due to its commoditization.
In addition, since Ethernet, and thus ERP, is virtually agnostic to all physical/server layer technologies,it can be supported any carrier’s network infrastructure. As a result, it is a more deployable and economically viable solution when compared with RPR.
The G.8032 protocol is optimized for ring topologies, and developed as a standardized alternative to replace the spanning tree protocol (STP) for fast transiting the port status without complex computation,provisioning overhead, and excessive information exchange, to thus achieve much faster (i.e., sub-50ms) protection switching. STP is a general (meshed) protocol which is applicable to any kind of networks. However, since it is generic, it does not have any optimization for ring topologies. STP needs much time (i.e., order of seconds) to rebuild topology because it needs information exchange for tree computing. Particularly for a ring, the tree computing is the selection of port to be blocked or opened.
The G.8032 protocol is focused to produce optimized process to handle ring protection and should be better performing all variants of STPs, including rapid spanning tree protocol (RSTP) and multiple spanning tree protocol (MSTP), in ring topologies.
In summary, G.8032 ERP is developed to meet the following objectives:
- To provide efficient network connectivity.
- To provide rapid service restoration (sub-50ms).
- To support multiple E-Services (e.g., E-LINE, E-TREE, E-LAN).
- To be client and server layer agnostic. That is, G.8032 ERP can be supported over (virtually)any physical/server layer and can transport (virtually) any Ethernet client.
- To utilize existing IEEE 802.1 bridging and IEEE 802.3 MAC hardware. Thus is simply asoftware increment on existing Ethernet switching equipment.
- To support flexible deployment models. To be deployed in Access, Metro, and Core network pplications
- To leverage Ethernet PHY bandwidth (e.g., 1/10/40/100GbE MAC), cost and time-to-marketcurves in support of cost effective and large bandwidth rings.
- To be standardized in ITU-T SG15/Q9.
- To translate into lower OPEX and CAPEX for the service provider
Terms and Concepts:
Ring Protection Link (RPL) – Link designated by mechanism that is blocked during Idle state to prevent loop on Bridged ring
RPL Owner – Node connected to RPL that blocks traffic on RPL during Idle state and unblocks during Protected state
Link Monitoring – Links of ring are monitored using standard ETH CC OAM messages (CFM)
Signal Fail (SF) – Signal Fail is declared when ETH trail signal fail condition is detected
No Request (NR) – No Request is declared when there are no outstanding conditions (e.g., SF, etc.) on the node
Ring APS (R-APS) Messages – Protocol messages defined in Y.1731 and G.8032
Automatic Protection Switching (APS) Channel - Ring-wide VLAN
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