162IPC configurationIPC overviewInter-Process Communication (IPC) is a reliable communication mechanism among processing units,typically CPUs. It is typically used on a distributed device or in an IRF fabric to provide reliable inter-cardor inter-device transmission. The following are the basic IPC concepts.NodeAn IPC node is an independent IPC-capable processing unit, typically, a CPU. Typically, distributeddevices and IRF fabrics have multiple IPC nodes, because each card or device in them has at least oneCPU.LinkAn IPC link is a connection between any two IPC nodes. There is one and only one link for packetsending and receiving between any two nodes. All IPC nodes are fully connected.IPC links are created when the system is initialized: When a node starts up, it sends handshake packetsto other nodes. It the handshake succeeds, a connection is established.The system uses link status to identify the link connectivity between two nodes. An IPC node can havemultiple links, each having its own status.ChannelA channel is a communication interface used by an upper layer application module of a node tocommunicate with an application module of a peer node. Each node assigns a locally unique channelnumber to each upper layer application module to identify this module.Data of an upper layer application module is sent to the IPC module through a channel, and the IPCmodule sends the data to a peer node through the link. The relationship between a node, link andchannel is as shown in Figure 56.
