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SAS enhances RPR routing

Jan 30, 20061 min

* Spatially Aware Sublayer optimizes the Resilient Packet Ring standard

SAS enhances RPR routing

By Jim Mckeon

The Resilient Packet Ring standard, IEEE 802.17, combines the reliability, service guarantees and management capabilities of SONET with the statistical efficiency of packet networks. A key new optimization of the technology, the Spatially Aware Sublayer, 802.17b, provides spatial reuse of the ring bandwidth via Layer 2 bridging.

Spatial reuse refers to the ability to send packets on only a portion of the ring circumference rather than around the entire ring, thus conserving bandwidth. By substituting simple Ethernet switches for expensive Layer 3 routers as ring elements, this new technology makes RPR an attractive solution for large companies and service providers.

The IEEE’s 802.17 Working Group began the standardization process for SAS following the ratification of the RPR standard in June 2004. Progress was swift; the current draft is stable and should be ratified in the second half of this year. With the technical details largely agreed on, products are shipping today that embody the standard and provide Layer 2 bridging in RPR.

To read more about how SAS enhnaces RPR routing, please go to:

McKeon is a product manager for Ethernet devices at Cortina Systems. He can be reached at