+--------------+
                                                     |              |
                                                 +-> | NTP Server 1 |
                                                 |   |              |
                           Shared cookie         |   +--------------+
+---------------+      encryption parameters     |   +--------------+
|               |    (Implementation dependent)  |   |              |
| NTS-KE Server | <------------------------------+-> | NTP Server 2 |
|               |                                |   |              |
+---------------+                                |   +--------------+
       ^                                         |          .
       |                                         |          .
       | 1. Negotiate parameters,                |          .
       |    receive initial cookie               |   +--------------+
       |    supply, generate AEAD keys,          |   |              |
       |    and receive NTP server IP            +-> | NTP Server N |
       |    addresses using "NTS Key                 |              |
       |    Establishment" protocol.                 +--------------+
       |                                                    ^
       |                                                    |
       |             +----------+                           |
       |             |          |                           |
       +-----------> |  Client  | <-------------------------+
                     |          |  2. Perform authenticated
                     +----------+     time synchronization
                                      and generate new
                                      cookies using "NTS
                                      Extension Fields for
                                      NTPv4".