page_title: Transparent Inter-process Communication
section_title: Inter Node Links
hierarchical_section_title: Transparent Inter-process Communication / Cluster / Inter Node Links
caption_attribution_description: English: Nodes are interconnected by one or two links
context_page_description: Transparent Inter Process Communication is an Inter-process communication service in Linux designed for cluster wide operation. It is sometimes presented as Cluster Domain Sockets, in contrast to the well-known Unix Domain Socket service; the latter working only on a single kernel.
context_section_description: A cluster consists of nodes interconnected with one or two links. A link constitutes a reliable packet transport service, sometimes referred to as an "L2.5" data link layer.
  It guarantees delivery and sequentiality for all packets.
  It acts as a trunk for inter-node connections, and keeps track of those.
  When all contact to the peer node is lost, sockets with connections to that peer are notified so they can break the connections.
  Each endpoint keeps track of the peer node's address bindings in the local replica of the service binding table.
  When contact to the peer node is lost all bindings from that peer are purged and service tracking events issued to all matching subscribers.
  When there is no regular data packet traffic each link is actively supervised by probing/heartbeats.
  Failure detection tolerance is configurable from 50 ms to 30 seconds, - default setting is 1.5 seconds.
  For performance and redundancy reasons it is possible to establish two links per node pair, - on separate network interfaces.
  A link pair can be configured for load sharing or active-standby.
  If a link fails there will be a disturbance-free failover to the remaining link, if any.
caption: Nodes are interconnected with one or two links
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