page_title: Multicast lightpaths
section_title: Concept of DBPP and SBPP on multicast connections
hierarchical_section_title: Multicast lightpaths / Concept of DBPP and SBPP on multicast connections
caption_attribution_description: English: Shared Backup Path Protection Before Failure
context_page_description: A multicast session requires a "point-to-multipoint" connection from a source node to multiple destination nodes. The source node is known as the root. The destination nodes are known as leaves. In the modern era, it is important to protect multicast connections in an optical mesh network. Recently, multicast applications have gained popularity as they are important to protecting critical sessions against failures such as fiber cuts, hardware faults, and natural disasters.
context_section_description: Dedicated backup path protection (DBPP) for multicast connections:
  Depending on the network topology, a dedicated backup path concept can be applied for multicast traffic. Fig 3 shows a multicast session from source node F to destination nodes A, B, C, D, and E which form the light tree. A dedicated backup path protection scheme can be applied to protect multicast traffic from link failure. This is easy to achieve with one-to-one protection where the dedicated backup path is already provisioned and traffic is simply switched to it on failure.
  Shared backup path protection (SBPP) for multicast connections:
  The SBPP technique can be used for multicast connections at the optical layer because of its resource efficiency, due to the fact that the backup paths can share wavelength channels on links while their corresponding primary paths are link disjoint. Paths can share links with working paths and protection paths of other leaves.
  In Fig 4 FE and FA are primary paths. The optical line is reserved for shared protection of both FE and FA.
  Path protection technique for multicast connections (multiple unicast connections):
caption: Fig 4:shared backup path protection before failure
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