target = "https://www.rfc-editor.org/rfc/rfc9000#section-7.4.1"

# 7.4.1.  Values of Transport Parameters for 0-RTT
#
# Using 0-RTT depends on both client and server using protocol
# parameters that were negotiated from a previous connection.  To
# enable 0-RTT, endpoints store the values of the server transport
# parameters with any session tickets it receives on the connection.
# Endpoints also store any information required by the application
# protocol or cryptographic handshake; see Section 4.6 of [QUIC-TLS].
# The values of stored transport parameters are used when attempting
# 0-RTT using the session tickets.
# 
# Remembered transport parameters apply to the new connection until the
# handshake completes and the client starts sending 1-RTT packets.
# Once the handshake completes, the client uses the transport
# parameters established in the handshake.  Not all transport
# parameters are remembered, as some do not apply to future connections
# or they have no effect on the use of 0-RTT.
# 
# The definition of a new transport parameter (Section 7.4.2) MUST
# specify whether storing the transport parameter for 0-RTT is
# mandatory, optional, or prohibited.  A client need not store a
# transport parameter it cannot process.
# 
# A client MUST NOT use remembered values for the following parameters:
# ack_delay_exponent, max_ack_delay, initial_source_connection_id,
# original_destination_connection_id, preferred_address,
# retry_source_connection_id, and stateless_reset_token.  The client
# MUST use the server's new values in the handshake instead; if the
# server does not provide new values, the default values are used.
# 
# A client that attempts to send 0-RTT data MUST remember all other
# transport parameters used by the server that it is able to process.
# The server can remember these transport parameters or can store an
# integrity-protected copy of the values in the ticket and recover the
# information when accepting 0-RTT data.  A server uses the transport
# parameters in determining whether to accept 0-RTT data.
# 
# If 0-RTT data is accepted by the server, the server MUST NOT reduce
# any limits or alter any values that might be violated by the client
# with its 0-RTT data.  In particular, a server that accepts 0-RTT data
# MUST NOT set values for the following parameters (Section 18.2) that
# are smaller than the remembered values of the parameters.
# 
# *  active_connection_id_limit
# 
# *  initial_max_data
# 
# *  initial_max_stream_data_bidi_local
# 
# *  initial_max_stream_data_bidi_remote
# 
# *  initial_max_stream_data_uni
# 
# *  initial_max_streams_bidi
# 
# *  initial_max_streams_uni
# 
# Omitting or setting a zero value for certain transport parameters can
# result in 0-RTT data being enabled but not usable.  The applicable
# subset of transport parameters that permit the sending of application
# data SHOULD be set to non-zero values for 0-RTT.  This includes
# initial_max_data and either (1) initial_max_streams_bidi and
# initial_max_stream_data_bidi_remote or (2) initial_max_streams_uni
# and initial_max_stream_data_uni.
# 
# A server might provide larger initial stream flow control limits for
# streams than the remembered values that a client applies when sending
# 0-RTT.  Once the handshake completes, the client updates the flow
# control limits on all sending streams using the updated values of
# initial_max_stream_data_bidi_remote and initial_max_stream_data_uni.
# 
# A server MAY store and recover the previously sent values of the
# max_idle_timeout, max_udp_payload_size, and disable_active_migration
# parameters and reject 0-RTT if it selects smaller values.  Lowering
# the values of these parameters while also accepting 0-RTT data could
# degrade the performance of the connection.  Specifically, lowering
# the max_udp_payload_size could result in dropped packets, leading to
# worse performance compared to rejecting 0-RTT data outright.
# 
# A server MUST reject 0-RTT data if the restored values for transport
# parameters cannot be supported.
# 
# When sending frames in 0-RTT packets, a client MUST only use
# remembered transport parameters; importantly, it MUST NOT use updated
# values that it learns from the server's updated transport parameters
# or from frames received in 1-RTT packets.  Updated values of
# transport parameters from the handshake apply only to 1-RTT packets.
# For instance, flow control limits from remembered transport
# parameters apply to all 0-RTT packets even if those values are
# increased by the handshake or by frames sent in 1-RTT packets.  A
# server MAY treat the use of updated transport parameters in 0-RTT as
# a connection error of type PROTOCOL_VIOLATION.

[[spec]]
level = "MUST"
quote = '''
The definition of a new transport parameter (Section 7.4.2) MUST
specify whether storing the transport parameter for 0-RTT is
mandatory, optional, or prohibited.
'''

[[spec]]
level = "MUST"
quote = '''
A client MUST NOT use remembered values for the following parameters:
ack_delay_exponent, max_ack_delay, initial_source_connection_id,
original_destination_connection_id, preferred_address,
retry_source_connection_id, and stateless_reset_token.
'''

[[spec]]
level = "MUST"
quote = '''
The client
MUST use the server's new values in the handshake instead; if the
server does not provide new values, the default values are used.
'''

[[spec]]
level = "MUST"
quote = '''
A client that attempts to send 0-RTT data MUST remember all other
transport parameters used by the server that it is able to process.
'''

[[spec]]
level = "MUST"
quote = '''
If 0-RTT data is accepted by the server, the server MUST NOT reduce
any limits or alter any values that might be violated by the client
with its 0-RTT data.
'''

[[spec]]
level = "MUST"
quote = '''
In particular, a server that accepts 0-RTT data
MUST NOT set values for the following parameters (Section 18.2) that
are smaller than the remembered values of the parameters.
'''

[[spec]]
level = "SHOULD"
quote = '''
The applicable
subset of transport parameters that permit the sending of application
data SHOULD be set to non-zero values for 0-RTT.
'''

[[spec]]
level = "MAY"
quote = '''
A server MAY store and recover the previously sent values of the
max_idle_timeout, max_udp_payload_size, and disable_active_migration
parameters and reject 0-RTT if it selects smaller values.
'''

[[spec]]
level = "MUST"
quote = '''
A server MUST reject 0-RTT data if the restored values for transport
parameters cannot be supported.
'''

[[spec]]
level = "MUST"
quote = '''
When sending frames in 0-RTT packets, a client MUST only use
remembered transport parameters; importantly, it MUST NOT use updated
values that it learns from the server's updated transport parameters
or from frames received in 1-RTT packets.
'''

[[spec]]
level = "MUST"
quote = '''
When sending frames in 0-RTT packets, a client MUST only use
remembered transport parameters; importantly, it MUST NOT use updated
values that it learns from the server's updated transport parameters
or from frames received in 1-RTT packets.
'''

[[spec]]
level = "MAY"
quote = '''
A
server MAY treat the use of updated transport parameters in 0-RTT as
a connection error of type PROTOCOL_VIOLATION.
'''