[radext] Terminology: Tickets, external and resumption PSKs in the RADIUS TLS-PSK draft

[Heikki Vatiainen <[e-mail]>]

The current RADIUS TLS-PSK draft introduces term 'ticket' in section 'PSK
Identities':
https://www.ietf.org/archive/id/draft-ietf-radext-tls-psk-09.html#name-psk-identities

In this section a reference is made to the TLS 1.3 RFC section 4.6.1 which
the describes the 'New Session Ticket Message'. My suggestion is to use
section 4.2.11 'Pre-Shared Key Extension' instead:
https://www.rfc-editor.org/rfc/rfc8446#section-4.2.11

The definitions therein boil down to this:

      struct {
          opaque identity<1..2^16-1>;
          uint32 obfuscated_ticket_age;
      } PskIdentity;

   identity:  A label for a key.  For instance, a ticket (as defined in
      Appendix B.3.4) or a label for a pre-shared key established
      externally.

With the above it's similarly clear that the identity is opaque.

The reasoning is this: this draft defines the use of external PSKs. Only
resumption PSKs sent by servers use 'New Session Ticket Message'. External
PSK labels are sent by clients using the 'Pre-Shared Key Extension'. In
other words, 'New Session Ticket Message' is not relevant with external
PSKs whose use this draft defines.

Also, when session resumption is turned off on the server side, 'New
Session Ticket Message' is never used. For these reasons it would be
clearer for the readers that the draft refers to messages that they'll see
with the external PSKs RADIUS TLS-PSK uses.

To summarise the above: be clear that 'ticket' is for resumption PSKs while
this draft targets on using external PSKs.

I've also created a pull request that tries to minimise different ways to
say 'external PSK' and 'session resumption PSK'.
https://github.com/radext-wg/draft-ietf-radext-tls-psk/pull/3

-- 
Heikki Vatiainen
[e-mail]