Overview of RRPP

Definition

The Rapid Ring Protection Protocol (RRPP) is a link layer protocol used to prevent loops on an Ethernet ring network.

Once a network is established, RRPP-enabled devices discover and eliminate loops on the network by blocking certain interfaces. If a network fault occurs, RRPP-enabled devices unblock blocked interfaces and switch data services to a functioning link.

Purpose

The ring network topology is applied to metropolitan area networks (MANs) and enterprise intranets to improve network reliability. If a fault occurs on a node or on a link between nodes, data services are switched to the backup link to ensure service. However, broadcast storms may occur on ring networks.

Many protocols can prevent broadcast storms on ring networks. However, if a fault occurs on a ring network, most protocols are slow to switch data services to the backup link. The network convergence is slow, causing service interruptions.

To shorten the convergence time and eliminate the impact of network scale on convergence time, Huawei developed RRPP. Compared with other Ethernet ring protocols, RRPP has the following advantages:

RRPP can be applied to large networks because the convergence time is not affected by the number of nodes on the ring network.
RRPP prevents broadcast storms caused by data loops when an Ethernet ring is complete.
If a fault occurs on an Ethernet ring network, the backup link rapidly restores the communication among the Ethernet ring network nodes.

**Table 1** Comparison of ring network protocols
Ring Network Protocol	Characteristics
Token ring	The token ring was the first ring technology introduced to the data communication field and applied in LANs. The token ring does not have the self-healing capability.
FDDI	Fiber Distributed Digital Interface (FDDI) is an improved token ring technology that uses a token to transmit the right to control a ring network. FDDI uses a double-ring structure. FDDI uses optical fibers for transmission, which greatly improves the performance and efficiency compared with the token ring. FDDI does not have self-healing capability. The bandwidth of an FDDI ring network cannot be efficiently utilized because FDDI uses source address stripping technology.
SDH/SONET	Synchronous Digital Hierarchy/Synchronous Optical Network (SDH/SONET) is a widely used ring technology that supports both single and multiple rings. SDH/SONET features high reliability and an automatic protection switching (APS)-based self-healing mechanism. On an SDH/SONET network, the bandwidth between two nodes is fixed and reserved based on its point-to-point (P2P) structure and the circuit switching design. The bandwidth cannot adapt to the actual situation, which leads to inefficient bandwidth use. As a result, the SDH/SONET technology cannot meet the bandwidth requirements of IP data services with frequent data bursts. In addition, broadcast and multicast packets on the SDH/SONET network are transmitted as unicast packets, wasting bandwidth. APS requires a maximum of 50% redundant bandwidth, which makes a flexible selection mechanism impossible.
RPR	Resilient Packet Ring (RPR) is a MAC-layer protocol on the ring topology developed and standardized by IEEE 802.17 and RPR alliance. RPR defines a logical P2P closed ring based on the MAC layer. On the physical layer, an RPR network is a ring network that consists of P2P links; on the data link layer, an RPR network is a broadcast network similar to an Ethernet network. RPR is implemented based on dedicated hardware and a complex fairness algorithm.
STP/RSTP/MSTP	The Spanning Tree Protocol (STP)/Rapid Spanning Tree Protocol (RSTP)/Multi-Spanning Tree Protocol (MSTP) builds a loop-free tree to prevent broadcast storms and implement redundancy backup. Multiple spanning trees perform load balancing and transmit traffic in different VLANs along different paths. As a protocol with the automatic calculation function, STP/RSTP/MSTP supports any topology. The network convergence time is affected by the topology.
RRPP	RRPP is short for Rapid Ring Protection Protocol. The network convergence time is not determined by the number of nodes on a ring network, so the convergence speed is fast. RRPP multi-instance supports load balancing of different types of service traffic. RRPP is a Huawei proprietary protocol.