Resilient Packet Ring Feature Guide

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Information About RPR
Resilient Packet Ring (RPR), as described in IEEE 802.17, is a metropolitan area network (MAN)
technology supporting data transfer among stations interconnected in a dual-ring configuration. This
protocol is very similar to Spatial Reuse Protocol (SRP), which was designed by Cisco and implemented
in Dynamic Packet Transport (DPT) products. New DPT interfaces have been designed to include the
802.17 RPR protocol and are available for multiple Cisco router platforms. This guide describes the RPR
interface and how to use RPR on compliant Cisco equipment.


Comparison of RPR with SRP and DPT Technologies
IEEE 802.17 RPR is very similar to the Cisco-developed SRP technology, which is used in the Cisco
DPT product line. Besides their different frame formats, other differences and similarities between IEEE
802.17 RPR and SRP can be summarized as follows:
• Fairness
– IEEE 802.17 RPR has a fairness algorithm that is used in the dynamic SRP-like mode suitable
for routing and switching applications.
– A third priority has been added for traffic that requires guaranteed bandwidth, but that is not
sensitive to latency and jitter.
• Protection
– SRP supports wrapping.
– IEEE 802.17 RPR supports systems that are capable of steering only protection.
– Cisco-implemented RPR supports both wrapping and steering for protection.
– Wrapping requires two stations to perform protection and suffers the least packet loss.


Configuring the Attribute Discovery Timer
Because station attributes are communicated separately from topology and protection packets, there is a
separate timer to control the frequency at which these packets are sent. Attribute propagation is therefore
determined by the attribute discovery (ATD) timer. The default rate is 1 packet for each ringlet per
second.
To configure the ATD timer, perform the following steps.