Overview of ERPS

Definition

ERPS is a protocol defined by the International Telecommunication Union - Telecommunication Standardization Sector (ITU-T) to eliminate loops at Layer 2. Because the standard number is ITU-T G.8032/Y1344, ERPS is also called G.8032. ERPS defines Ring Auto Protection Switching (RAPS) Protocol Data Units (PDUs) and protection switching mechanisms.

ERPS has two versions: ERPSv1 released by ITU-T in June 2008 and ERPSv2 released in August 2010. ERPSv2, fully compatible with ERPSv1, provides the following enhanced functions:

Multi-ring topologies, such as intersecting rings
RAPS PDU transmission on virtual channels (VCs) and non-virtual-channels (NVCs) in sub-rings
Forced Switch (FS) and Manual Switch (MS)
Revertive and non-revertive switching

Purpose

Generally, redundant links are used on an Ethernet switching network such as a ring network to provide link backup and enhance network reliability. The use of redundant links, however, may produce loops, causing broadcast storms and rendering the MAC address table unstable. As a result, communication quality deteriorates, and communication services may even be interrupted. Table 1 describes ring network protocols supported by devices.

**Table 1** Ring network protocols supported by devices
Ring Network Protocol	Advantage	Disadvantage
RRPP	Provides fast convergence and carrier-class reliability.	Supports only level-1 sub-ring in ring networking. Is a Huawei proprietary protocol that cannot be used for communication between Huawei and non-Huawei devices.
STP/RSTP/MSTP	Applies to all Layer 2 networks. Is a standard IEEE protocol that allows Huawei devices to communicate with non-Huawei devices.	Provides low convergence on a large network, which cannot meet the carrier-class reliability requirement.
SEP	Applies to all Layer 2 networks. Provides fast convergence and carrier-class reliability. Displays the topology of an entire ring, facilitating fault location and device maintenance.	Is a Huawei proprietary protocol that cannot be used for communication between Huawei and non-Huawei devices.
ERPS	Provides fast convergence and carrier-class reliability. Is a standard ITU-T protocol that allows Huawei devices to communicate with non-Huawei devices. Supports single-ring and multi-ring topologies in ERPSv2.	Requires the network topology to be planned in advance. The configuration is complex.

Ethernet networks demand faster protection switching. STP does not meet the requirement for fast convergence. RRPP and SEP are Huawei proprietary ring protocols, which cannot be used for communication between Huawei and non-Huawei devices on a ring network.

ERPS, a standard ITU-T protocol, prevent loops on ring networks. It optimizes detection and performs fast convergence. ERPS allows all ERPS-capable devices on a ring network to communicate.

Benefits

Prevents broadcast storms and implements fast traffic switchover on a network where there are loops.
Provides fast convergence and carrier-class reliability.
Allows all ERPS-capable devices on a ring network to communicate.