Security Considerations under XEP for PING (XEP-0199) states this - "If a connected resource receives a ping request but it does not want to reveal its network availability to the sender for any reason (e.g., because the sender is not authorized to know the connected resource's availability), then it too MUST reply with a <service-unavailable/> error."
How does one determine if the sender is authorized or not authorized to know the connected resources's availability? -- Priya
