Just a note on NAI realm.  2.1.3 says:

  For example, the NAI @realm can safely be
   reused since it does not provide any specific information to
   associate a user's resumption attempt with the original full
   handshake.  However, reusing the NAI
   P2ZIM2F+OEVAO21nNWg2bVpgNnU=@realm enables an on-path attacker to
   associate a resumption attempt with the original full handshake.  The
   TLS PSK identity is typically derived by the TLS implementation and
   may be an opaque blob without a routable realm.  The TLS PSK identity
   is therefore in general unsuitable for deriving a NAI to use in the
   Identity Response.

  This text is good, but could perhaps be clearer.  It's not obvious where the 
NAI "P2ZIM2F+OEVAO21nNWg2bVpgNnU=@realm" comes from.  The subsequent text 
referring to TLS PSK identity is, in fact, unrelated.  But having the two 
subjects next to each other could be misleading.

  i.e. discuss "P2ZIM2F+OEVAO21nNWg2bVpgNnU=@realm"  in the context of an NAI 
which is secure, and hides identities, but is unique and allows tracking.

  Separately, discuss TLS PSK Identity.

  Perhaps it would be good to note that the TLS PSK identity is only used by 
the TLS layer, and therefore is entirely unrelated to the EAP Response 
Identity.  As such, from the standpoint of layer separation, the TLS PSK 
identity MUST NOT be used to derive an EAP Response Identity.

  It may also be worth noting that like RFC 7542, this document uses "@realm" 
as a short-hand for the realm.  But also that single-label realm names are 
forbidden by RFC 7542 Section 2.2.

  Alan DeKok.

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