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+---
+title: "Recursive layers"
+author: "Dimitri Staessens"
+#description: "IRMd"
+date:  2019-07-23
+weight: 20
+#type:  page
+draft: false
+description: >
+    How to build a recursive network.
+---
+
+The most important structure in recursive networks are the layers,
+that are built op from [elements](/docs/elements/) called
+Inter-Process Communication Processes (IPCPs). (Note again that the
+layers in recursive networks are not the same as layers in the OSI
+model).
+
+{{<figure width="50%" src="/docs/concepts/creating_layers.jpg">}}
+
+Now, the question is, how do we build these up these layers? IPCPs are
+small programs (think of small virtual routers) that need to be
+started, configured and managed. This functionality is usually
+implemented in some sort of management daemon. Current RINA
+implementations call it the *IPC manager*, Ouroboros calls it the
+__IPC Resource Management daemon__ or __IRMd__ for short. The IRMd
+lies at the heart of each system that is participating in an Ouroboros
+network, implementing the core function primitives. It serves as the
+entry point for the system/network administrator to manage the network
+resources.
+
+We will describe the functions of the Ouroboros IRMd with the
+Ouroboros commands for illustration and to make things a bit more
+tangible.
+
+The first set of primitives, __create__ (and __destroy__), allow
+creating IPCPs of a given *type*. This just runs the process without
+any further configuration. At this point, that process is not part of
+any layer.
+
+```
+$ irm ipcp create type unicast name my_ipcp
+$ irm ipcp list
++---------+----------------------+------------+----------------------+
+|     pid |                 name |       type |                layer |
++---------+----------------------+------------+----------------------+
+|    7224 |              my_ipcp |    unicast |         Not enrolled |
++---------+----------------------+------------+----------------------+
+```
+
+The example above creates a unicast IPCP and gives that IPCP a name
+(we called it "my_ipcp"). A listing of the IPCPs in the system shows
+that the IPCP is running as process 7224, and it is not part of a
+layer ("*Not enrolled*").
+
+To create a new functioning network layer, we need to configure the
+IPCP, using a primitive called __bootstrapping__. Bootstrapping sets a
+number of configuration optionss for the layer (such as the routing
+algorithm to use) and activates the IPCP to allow it to start
+providing flows.  The Ouroboros command line allows creating an IPCP
+with some default values, that are a bit like a vanilla IPv4 network:
+32-bit addresses and shortest-path link-state routing.
+
+```
+$ irm ipcp bootstrap name my_ipcp layer my_layer
+$ irm ipcp list
++---------+----------------------+------------+----------------------+
+|     pid |                 name |       type |                layer |
++---------+----------------------+------------+----------------------+
+|    7224 |              my_ipcp |    unicast |             my_layer |
++---------+----------------------+------------+----------------------+
+```
+
+Now we have a single node-network. In order to create a larger
+network, we connect and configure new IPCPs using a third primitive
+called __enrollment__. When enrolling an IPCP in a network, it will
+create a flow (using a lower layer) to an existing member of the
+layer, download the bootstrapping information, and use it to configure
+itself as part of this layer.
+
+The final primitive is the __connect__ (and __disconnect__)
+primitive. This allows to create *adjacencies* between network nodes.
+
+An example of how to create a small two-node network is given in
+[tutorial 2](/docs/tutorials/tutorial-2/)
+
+---
+Changelog:
+
+2019-07-23: Initial version