Draft: draft-ietf-tls-ticketrequests

Commentary: hopefully nothing too outlandish in here 
 Thanks !
TLS session tickets enable stateless connection resumption for
clients without server-side, per-client state.  Servers vend an
arbitrary number of session tickets to clients, at their discretion,
upon connection establishment.  Clients store and use tickets when
resuming future connections.  This document describes a mechanism by
which clients can specify the desired number of tickets needed for
future connections.  This extension aims to provide a means for
servers to determine the number of tickets to generate in order to
reduce ticket waste, while simultaneously priming clients for future
connection attempts.
TLS session tickets enable stateless connection resumption for
clients without server-side, per-client, state.  Servers vend an
arbitrary number of session tickets to clients, at their discretion,
upon connection establishment.  Clients store and use tickets when
resuming future connections.  This document describes a mechanism by
which clients can specify the desired number of tickets needed for
future connections.  This extension aims to provide a means for
servers to determine the number of tickets to generate in order to
reduce ticket waste, while simultaneously priming clients for future
connection attempts.
This document specifies a new TLS extension - "ticket_request" - that
can be used by clients to express their desired number of session
tickets.  Servers can use this extension as a hint of the number of
NewSessionTicket messages to vend.  This extension is only applicable
to TLS 1.3 RFC8446, DTLS 1.3 I-D.ietf-tls-dtls13, and future versions
thereof.
This document specifies a new TLS extension - "ticket_request" - that
can be used by clients to express their desired number of session
tickets.  Servers can use this extension as a hint for the number of
NewSessionTicket messages to vend.  This extension is only applicable
to TLS 1.3 RFC8446, DTLS 1.3 I-D.ietf-tls-dtls13, and future versions
of (D)TLS.
The number of tickets desired by the client when the server is
willing to resume using the presented ticket.
The number of tickets desired by the client when the server is
willing to resume using a ticket presented in this ClientHello.
IANA is requested to Create an entry, ticket_request(TBD), in the
existing registry for ExtensionType (defined in RFC8446), with "TLS
being set to "Yes".
IANA is requested to create an entry, ticket_request(TBD), in the
existing registry for ExtensionType (defined in RFC8446), with "TLS
being set to "Y".
Ticket re-use is a security and privacy concern.  Moreover, clients
must take care when pooling tickets as a means of avoiding or
amortizing handshake costs.  If servers do not rotate session ticket
encryption keys frequently, clients may be encouraged to obtain and
use tickets beyond common lifetime windows of, e.g., 24 hours.
Despite ticket lifetime hints provided by servers, clients SHOULD
dispose of pooled tickets after some reasonable amount of time that
mimics the ticket rotation period.
Ticket re-use is a security and privacy concern.  Moreover, clients
must take care when pooling tickets as a means of avoiding or
amortizing handshake costs.  If servers do not rotate session ticket
encryption keys frequently, clients may be encouraged to obtain and
use tickets beyond common lifetime windows of, e.g., 24 hours.
Despite ticket lifetime hints provided by servers, clients SHOULD
dispose of pooled tickets after some reasonable amount of time that
mimics the session ticket encryption key rotation period.
In some cases, a server may send NewSessionTicket messages
immediately upon sending the server Finished message rather than
waiting for the client Finished.  If the server has not verified the
client's ownership of its IP address, e.g., with the TLS Cookie
extension (see RFC8446; Section 4.2.2), an attacker may take
advantage of this behavior to create an amplification attack
proportional to the count value toward a target by performing a key
exchange over UDP with spoofed packets.  Servers SHOULD limit the
number of NewSessionTicket messages they send until they have
verified the client's ownership of its IP address.
In some cases, a server may send NewSessionTicket messages
immediately upon sending the server Finished message rather than
waiting for the client Finished.  If the server has not verified the
client's ownership of its IP address, e.g., with the TLS Cookie
extension (see RFC8446; Section 4.2.2), an attacker may take
advantage of this behavior to create an amplification attack
proportional to the count value toward a target by performing a
(DTLS) key exchange over UDP with spoofed packets.  Servers SHOULD
limit the number of NewSessionTicket messages they send until they
have verified the client's ownership of its IP address.