Secure Shell (SSH) is the mandatory transport protocol for Network Configuration Protocol (NETCONF). NETCONF, which is described in Request for Comments (RFC) 6241, provides the ability to automate the configuration of network devices. Protocol messages are encoded by using an Extensible Markup Language (XML) based format.

Simple Network Management Protocol (SNMP) is not the mandatory transport protocol for NETCONF. Although SNMP is used to monitor network devices, it is not typically used to manage network devices. NETCONF was created to address this lack of standardized functionality.

Simple Object Access Protocol (SOAP) is not the mandatory transport protocol for NETCONF. However, SOAP can be used to transport NETCONF.

YANG is not the mandatory transport protocol for NETCONF. YANG, which is defined in RFC 6020, is a hierarchical data modeling language that can model configuration and state data for NETCONF. The YANG data can be encoded in an XML format.