Authorization
  Client    Server
    |         |
    |<=======>| DTLS Connection Establishment
    |         |   and mutual authentication
    |         |
A:  +-------->| Header: POST (Code=0.02)
    |  POST   | Uri-Path:"token"
    |         | Content-Format: application/ace+cbor
    |         | Payload: <Request-Payload>
    |         |
B:  |<--------+ Header: 2.05 Content
    |  2.05   | Content-Format: application/ace+cbor
    |         | Payload: <Response-Payload>
    |         |