Patent ID: 8724452

Claim:
A method for protecting traffic in a Layer 2 (L2) communication network between a first and a second local nodes (CE 1 , CE 2 ) interconnected via a dual homed structure, wherein said structure comprises: four provider edge nodes PEs, four communication lines and four local connections, a first pair of the provider edge nodes (PEs A,C) being respectively connected by a first couple of local connections from among the four local connections (CE 1 -PEs A,C) to the first local node (CE 1 ), a second pair of the provider edge nodes (PEs B,D) respectively connected by a second couple of local connections from among the four local connections (CE 2 -PEs B,D) to the second local node (CE 2 ), two distant communication lines (P-PW) from among the four communication lines each interconnecting two provider edge nodes PEs belonging to different pairs, and two local communication lines (S-PW) from among the four communication lines each interconnecting two provider edge nodes PEs belonging to the same pair; the method comprising the steps of: a) in a fault-free state, carrying traffic from the first local node (CE 1 ) to the second local node (CE 2 ) by dividing it into two traffic flows at the first local node (CE 1 ) and respectively carrying the two flows via the first couple of local connections, via the provider edge nodes PEs of said first pair, via said two distant communication lines, via the provider edge nodes (PEs) of said second pair, and via the second couple of local connections, while carrying said two flows via both the provider edge nodes (PEs) of said second pair; b) in a faulty state, when a failure occurs in at least one element of a group comprising a local connection (CE 1 -PE) and a provider edge node (PE): propagating Layer 2 fault indications (L2 OAM tools) in the dual homed structure and processing thereof at the PEs so that as a result of said failure, the failed element, the remaining element of the group associated with it and also the local and the distant communication lines associated with said PE element of the group become blocked for said two traffic flows in the dual homed structure, while a specific one of said first and second local nodes CE 1 and CE 2 , being remote from the failure, remains unaware of the failure; performing switching at the local node being closer to the failure, so that both said two flows are directed to unblocked members of the dual homed structure, and rearranging said traffic flows based on the physical and said Layer 2 fault indications, so as to bypass all said blocked members of the dual homed structure by utilizing the remaining ones to carry both of said two flows, while both of the flows, arriving from the first local node (CE 1 ) to the second local node (CE 2 ) upon the mentioned failure, pass through both provider edge node (PEs) associated with the second local node (CE 2 ) in case they are both functional, thereby allowing the PEs associated with the second local node to learn MAC addresses sent by CE 1 .