target = "https://www.rfc-editor.org/rfc/rfc9000#section-12.3"

# 12.3.  Packet Numbers
#
# The packet number is an integer in the range 0 to 2^62-1.  This
# number is used in determining the cryptographic nonce for packet
# protection.  Each endpoint maintains a separate packet number for
# sending and receiving.
# 
# Packet numbers are limited to this range because they need to be
# representable in whole in the Largest Acknowledged field of an ACK
# frame (Section 19.3).  When present in a long or short header,
# however, packet numbers are reduced and encoded in 1 to 4 bytes; see
# Section 17.1.
# 
# Version Negotiation (Section 17.2.1) and Retry (Section 17.2.5)
# packets do not include a packet number.
# 
# Packet numbers are divided into three spaces in QUIC:
# 
# Initial space:  All Initial packets (Section 17.2.2) are in this
#    space.
# 
# Handshake space:  All Handshake packets (Section 17.2.4) are in this
#    space.
# 
# Application data space:  All 0-RTT (Section 17.2.3) and 1-RTT
#    (Section 17.3.1) packets are in this space.
# 
# As described in [QUIC-TLS], each packet type uses different
# protection keys.
# 
# Conceptually, a packet number space is the context in which a packet
# can be processed and acknowledged.  Initial packets can only be sent
# with Initial packet protection keys and acknowledged in packets that
# are also Initial packets.  Similarly, Handshake packets are sent at
# the Handshake encryption level and can only be acknowledged in
# Handshake packets.
# 
# This enforces cryptographic separation between the data sent in the
# different packet number spaces.  Packet numbers in each space start
# at packet number 0.  Subsequent packets sent in the same packet
# number space MUST increase the packet number by at least one.
# 
# 0-RTT and 1-RTT data exist in the same packet number space to make
# loss recovery algorithms easier to implement between the two packet
# types.
# 
# A QUIC endpoint MUST NOT reuse a packet number within the same packet
# number space in one connection.  If the packet number for sending
# reaches 2^62-1, the sender MUST close the connection without sending
# a CONNECTION_CLOSE frame or any further packets; an endpoint MAY send
# a Stateless Reset (Section 10.3) in response to further packets that
# it receives.
# 
# A receiver MUST discard a newly unprotected packet unless it is
# certain that it has not processed another packet with the same packet
# number from the same packet number space.  Duplicate suppression MUST
# happen after removing packet protection for the reasons described in
# Section 9.5 of [QUIC-TLS].
# 
# Endpoints that track all individual packets for the purposes of
# detecting duplicates are at risk of accumulating excessive state.
# The data required for detecting duplicates can be limited by
# maintaining a minimum packet number below which all packets are
# immediately dropped.  Any minimum needs to account for large
# variations in round-trip time, which includes the possibility that a
# peer might probe network paths with much larger round-trip times; see
# Section 9.
# 
# Packet number encoding at a sender and decoding at a receiver are
# described in Section 17.1.

[[spec]]
level = "MUST"
quote = '''
Subsequent packets sent in the same packet
number space MUST increase the packet number by at least one.
'''

[[spec]]
level = "MUST"
quote = '''
A QUIC endpoint MUST NOT reuse a packet number within the same packet
number space in one connection.
'''

[[spec]]
level = "MUST"
quote = '''
If the packet number for sending
reaches 2^62-1, the sender MUST close the connection without sending
a CONNECTION_CLOSE frame or any further packets; an endpoint MAY send
a Stateless Reset (Section 10.3) in response to further packets that
it receives.
'''

[[spec]]
level = "MUST"
quote = '''
A receiver MUST discard a newly unprotected packet unless it is
certain that it has not processed another packet with the same packet
number from the same packet number space.
'''

[[spec]]
level = "MUST"
quote = '''
Duplicate suppression MUST
happen after removing packet protection for the reasons described in
Section 9.5 of [QUIC-TLS].
'''