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CONNECTIVITY FAULT MANAGEMENT (CFM) BASED SPANNING TREE PROTOCOL (xSTP) RE-CONVERGENCE

IP.com Disclosure Number: IPCOM000250071D
Publication Date: 2017-May-25
Document File: 9 page(s) / 520K

Publishing Venue

The IP.com Prior Art Database

Abstract

The present disclosure relates to Connectivity Fault Management (CFM) based Spanning Tree Protocol (xSTP) re-convergence. The present disclosure provides faster convergence in xSTP during indirect failure scenarios, traffic blackholing and loop avoidance in xSTP unidirectional link failure scenarios, the use of Ethernet Connectivity Fault Management (ECFM) Operations, Administration, and Maintenance (OAM) capabilities such as CFM loopback and traceroute in debugging such links, CFM defects/notifications on Maintenance End Points (MEPs) associated with xSTP links to provide better picture of events while debugging field issues related to xSTP, and xSTP switching based on signal degrade which is helpful in networks having intermittent losses over links used by STP.

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CONNECTIVITY FAULT MANAGEMENT (CFM) BASED SPANNING TREE PROTOCOL (xSTP) RE-CONVERGENCE

ABSTRACT

The present disclosure relates to Connectivity Fault Management (CFM) based Spanning Tree Protocol (xSTP) re-convergence.  The present disclosure provides faster convergence in xSTP during indirect failure scenarios, traffic blackholing and loop avoidance in xSTP unidirectional link failure scenarios, the use of Ethernet Connectivity Fault Management (ECFM) Operations, Administration, and Maintenance (OAM) capabilities such as CFM loopback and traceroute in debugging such links, CFM defects/notifications on Maintenance End Points (MEPs) associated with xSTP links to provide better picture of events while debugging field issues related to xSTP, and xSTP switching based on signal degrade which is helpful in networks having intermittent losses over links used by STP.

 

DETAILED DESCRIPTION

Again, the present disclosure relates to Connectivity Fault Management (CFM) based Spanning Tree Protocol (xSTP) re-convergence.  Spanning Tree Protocols (STP) prevent loops from being formed when switches or bridges are interconnected via multiple paths.  The “x” in xSTP denotes various different STPs are contemplated. 

The present disclosure provides:

·         faster convergence in xSTP during indirect failure scenarios,

·         traffic blackholing and loop avoidance in xSTP unidirectional link failure scenarios,

·         the use of Ethernet Connectivity Fault Management (ECFM) Operations, Administration, and Maintenance (OAM) capabilities such as CFM loopback and traceroute in debugging such links,

·         CFM defects/notifications on Maintenance End Points (MEPs) associated with xSTP links to provide better picture of events while debugging field issues related to xSTP, and

·         xSTP switching based on signal degrade which is helpful in networks having intermittent losses over links used by STP.

When xSTP is deployed with links over repeaters, SDH/SONET networks, L2CFT (Layer 2 Control Frame Tunneling) enabled bridges or other xSTP disabled bridges; there can be following issues with respect to re-convergence.  Here, the solution is described to avoid problems during indirect/unidirectional link failures.  Also, the re-convergence of xSTP is described based on Signal Degrade.

As shown in Figure-A below, nodes A, B, C, & D are running xSTP with links over different STP unaware elements. 

 


Problem 1:

As shown in Figure-B below, if there is an indirect link failure (e.g., a failure between SDH/SONET X & Y devices) on a link between node A and node B, for which Node A port P1 & Node B port P2 will not detect loss of signal.  As Node B port P2 is a root port and it will stop receiving Spanning Tree Protocol (STP) Bridge Protocol Data Units (BPDUs) but will still transmit BPDU’s through port P3, with Node A’s root bridge information and after 3X hello time = 6 seconds, xSTP convergence will be initiated.  Here, three missing Hello BPDU’s in a row will cause port P2 on Node...