Positive Response:

If the device was able to satisfy the request,
an <rpc-reply> is sent that contains an <ok> element.

Negative Response:

An <rpc-error> element is included in the <rpc-reply>
if the request cannot be completed for any reason.
A validate operation can fail for any of the following reasons:
+  Syntax errors
+  Missing parameters
+  References to undefined configuration data

<rpc message-id="101" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
    <validate>
        <source>
            <candidate/>
        </source>
    </validate>
</rpc>