RPR (redirected from Resilient Packet Ring)

Rally for the Republic (RPR)

 or Gaullists

Former French political party. It was founded by Jacques Chirac in 1976 as the successor to the various Gaullist coalitions that dominated the political life of the Fifth Republic under Charles de Gaulle and Georges Pompidou. The party had its antecedents in the group Rally of the French People, organized by de Gaulle in 1947. It evolved into the Union for the New Republic (1958–62) and then the Union of Democrats for the New Republic (1968–76) before assuming the name Rally for the Republic. In 2002 the party merged with the Liberal Democratic party and much of the Union for the French Democracy to form the Union for a Popular Movement.

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RPR

(Resilient Packet Ring) A packet-based protocol that provides fault tolerance and statistical multiplexing for the metropolitan and national SONET and Ethernet networks of the carriers. The RPR architecture is often added to SONET networks to enable them to carry packets. RPR is a data link layer protocol (layer 2) that uses dual counter-rotating rings for fault tolerance.

RPR nodes, which contain the RPR interface cards, are typically routers and switches in a packet environment (Ethernet) or add/drop multiplexers (ADMs) in a TDM environment (SONET). The IEEE has standardized RPR with its 802.17 specification.

Counter-Rotating Rings
RPR nodes are connected in a ring topology by two fibers, each transmitting in the opposite direction. Both inner and outer ringlets are active at the same time. If a failure occurs, traffic capacity is decreased.

Packets move through every node in the ring up to the destination node, where they are stripped off. In an RPR, traffic from multiple nodes travels on the ring concurrently.

RPR includes a "fairness" algorithm. Since packets pass through all intermediate nodes, a node can notify the others to slow the transmission if it cannot get its fair share of bandwidth on the ring to transmit. This traffic adjustment enhances the statistical multiplexing and ensures fair access during congestion. Since SONET interleaves fixed channels, "RPR over SONET" turns SONET into a more dynamic network. See TDM network, SONET and statistical multiplexor.

Normal Operation

Under normal operation, data flows in both ringlet 0 and ringlet 1. In case of failure, overall bandwidth is reduced.

Wrapping the Packets

If a line breaks, the ring is reconfigured using ringlet 0 and 1 together. RPR "wrapping" causes the two nodes at either side of the break to become return nodes and provides the fastest recovery.

Steering the Packets

RPR "steering" can restore a damaged network and also shorten the number of hops packets take compared to wrapping. However, steering takes a little bit longer to complete as all nodes in the network have to be reconfigured. Sometimes, wrapping is performed immediately, and steering is performed afterwards.