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Prevention of network loops in a ring topology caused by processing stale NR,RB PDUs by propagating WTR timer value in RAPS PDU

IP.com Disclosure Number: IPCOM000256761D
Publication Date: 2018-Dec-28

Publishing Venue

The IP.com Prior Art Database


This disclosure provides using WTR timer propagation for preventing loops caused by stale NR, RB PDUs. This disclosure proposes extension to the RAPS PDU frame format, by adding an organizational specific TLV to RAPS PDU, representing the value of WTR timer. The reception of an old RAPS PDU may result in erroneous ring state processing by ethernet nodes. The guard timer is used to prevent nodes from acting upon outdated RAPS PDU but we might land up in situation where we receive a stale RAPS PDU after the expiry of guard timer and cause loop in the network. This problem is seen in customer's networks to take down all the services and is not recoverable until user intervention. This disclosure provides a solution for preventing loops caused only by stale NR, RB PDUs. As described herein, the RPLowner will transmit the value of WTR timer in the RAPS PDU and all the other nodes will store this value as ring restoration time (RRT). Whenever a local fault clear will occur on a nodes, a RRT timer along with guard timer will start. Any NR,RB PDU received before the expiry of RRT timer will not be processed as No NR,RB PDU is expected to be received before the rpl owner reverts back.