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Method for replication and protection for packet over SONET interfaces

IP.com Disclosure Number: IPCOM000125747D
Publication Date: 2005-Jun-15
Document File: 5 page(s) / 473K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for replication and protection for packet over synchronous optical network (SONET) interfaces. Benefits include improved functionality and improved performance

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Method for replication and protection for packet over SONET interfaces

Disclosed is a method for replication and protection for packet over synchronous optical network (SONET) interfaces. Benefits include improved functionality and improved performance.

Background

              “PPP Over SONET/SDH”, RFC2615, dated June 1999, owned by Internet Engineering Task Force (Network Working Group) of the American National Standards Institution (ANSI) describes point-to-point packet transfer over SONET interfaces.

              “Packet Over SONET Physical Layer Interface”, dated December 1998, owned by SATURN Development Group is the standard for POS-PHY interfaces. SATURN is a registered trademark of PMC-Sierra, Inc. POS-PHY is a trademark of PMC-Sierra, Inc.

              Safety critical embedded systems must be fail-safe. Safety is often ensured by making such systems redundant. The lowest level of redundancy is often at the module level, where a module is a card in the system chassis (see Figure 1).

              Modules are typically embedded in pairs within a safety critical system. At run time, one module of the pair is active while the other is in standby mode. The software running on both modules is the same. To maintain synchronization, external events are replicated to both cards.

              The difference between active and standby modules at run time is that active modules have access to input/output (I/O), such as disks and communications busses, while the standby module does not. If a failure is detected on an active module, an automatic protection switch (APS) occurs and the module previously in standby mode becomes active. As a result, service is not interrupted.

              In redundant systems, designers seek to achieve two replication goals:

•             Execution path on the active module to be as similar as possible to the execution path of the standby module

•             Avoiding duplication and contention on the external bus by making sure that only the active module writes data to the bus

General description

              The disclosed method is an efficient technique to handle replication and APS on the packet over SONET (POS) interface. The method uses mapping and polling registers on Internet exchange point (IXP) POS-PHY level-2 coprocessors.

Advantages

              The disclosed method provides advantages, including:
•             Improved functionality due to providing replication and protection for POS interfaces

•             Improved functionality due to enabling arbitration to be handled by the coprocessor setting the physical-to-logical translation register at configuration or APS

•             Improved functionality due to enabling software to submit buffers for transmission regardless of whether it is running on a standby or active module
•             Improved performance due to performing one read and two write operations for an APS

•             Improved performance due to not requiring arbitration for writing to the POS I/O bu...