Transport Layer Security (TLS) Session Resumption without Server-Side State
draft-salowey-tls-ticket-07

[Ballot discuss]
Generally,  I think is good stuff, and I expect to vote "Yes" eventually.  I'm concerned, though, about how the draft specifies the server's behavior in the case where a ticket is not honored.  Currently, the draft says:

  If the server cannot or does not want to honor the ticket then it can initiate a full handshake
  with the client.

I believe it would be valuable to expand this to describe in detail what happens when the server does not honor a specific ticket but would be willing to provide a new ticket (as, for example, when the ticket has expired) and to distinguish it from cases where the server is not willing to honor any tickets at
this time.  While some of this can be inferred from section 3.3 and 3.4, I think clarification will improve the likelihood of interoperable implementations.  Examples of the type given in 3.1 would be one way to achieve this.

The document also says:

  TLS clients may be given a hint of the lifetime of the ticket.  Since the lifetime of a ticket may be
  unspecified a client has its own local policy which determines when it discards tickets. 

If given, is this hint provided in an established format?  If so, a pointer to that format would be valuable.    If not, some guidance on the necessary elements of a hint would be useful, especially
in light of this statement:

  Clients MUST NOT examine the ticket under the assumption that it
  complies with this document.

The timestamp in the ticket allows the server to expire the ticket, but the client cannot use this
structure to infer the timestamp.  I assume, then, that it must either receive hints which indepdently
reference the time of origination, that the hints use some independent format for time of expiry,
or that it must assume the time of receipt plus some delta (e.g. 24 hours) is appropriate.

IANA Last Call Comments:
Upon approval of this document the IANA will assign a TLS extension number (the value 35 is suggested) to the SessionTicket TLS extension in the following registry:
http://www.iana.org/assignments/tls-extensiontype-values

IANA will also assign a TLS HandshakeType number to the SessionTicket handshake type located at the following registry:
http://www.iana.org/assignments/tls-parameters

Please confirm that IANA understands these assignments to go in appropriate registries as described above.