NETCONF Call Home and ConfD

There has been quite a bit of interest from customers in the NETCONF Call Home feature which is described in RFC 8071, “NETCONF Call Home and RESTCONF Call Home”.  Normally, we would have waited to release a new feature in the next major release (7.1), but due to customer demand, we released it early as part of ConfD 6.7.1.

Normally in NETCONF, the NETCONF client in the orchestrator or controller initiates the connection to the NETCONF server in the network element.  However, for certain use cases such as the presence of firewalls or NAT, it is useful to have Call Home functionality where the connection process is reversed and the NETCONF server initiates the connection to the NETCONF client.

RFC 8071 has standardized this process.  For a normal NETCONF connection, the NETCONF client first establishes a TCP connection to the NETCONF server and then starts up SSH followed by NETCONF over this TCP connection.  Using NETCONF Call Home, the NETCONF server establishes the TCP connection to the NETCONF client (reverse of the normal process) and then the NETCONF client starts up SSH and NETCONF as normal.  Therefore, to use NETCONF Call Home, both the NETCONF server and the NETCONF client need to provide support for it.  ConfD provides the NETCONF server support for NETCONF Call Home.

It is also of interest to note that the NETCONF Call Home RFC does not address what the NETCONF client should do once the NETCONF session is started using NETCONF Call Home.  i.e. There is no standard NETCONF <hello-how-may-I-help-you> RPC.  That will be addressed in future RFCs which make use of NETCONF Call Home or in an application-specific manner.

This month’s application note takes a look at the new “NETCONF Call Home and ConfD.”  The application note builds on prerequisite material which can be found in the ConfD User Guide and the two NETCONF Call Home examples in the ConfD distribution which can be found under examples.confd/netconf_call_home.  The application note also discusses ways of doing simple NETCONF Call Home testing using the netconf-console utility program which is included in the ConfD distribution.

Download your copy of the application note here.

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