Every <rpc> element contains a mandatory attribute, the message-id. This attribute has a unique value for every RPC request, and is used to associate and reconcile every RPC request with its corresponding response. The message-id value is a monotonically increasing integer string. The maximum length of this string is 4095 characters. If the message-id is not present in the RPC request, the server rejects the request by returning an <rpc-error> with an <error-tag> element set to “missing-attribute”.
If there are any additional attributes present in the RPC request, the NETCONF server returns them unmodified in the corresponding RPC reply.