target = "https://www.rfc-editor.org/rfc/rfc9000#section-8.2.4"

# 8.2.4.  Failed Path Validation
#
# Path validation only fails when the endpoint attempting to validate
# the path abandons its attempt to validate the path.
# 
# Endpoints SHOULD abandon path validation based on a timer.  When
# setting this timer, implementations are cautioned that the new path
# could have a longer round-trip time than the original.  A value of
# three times the larger of the current PTO or the PTO for the new path
# (using kInitialRtt, as defined in [QUIC-RECOVERY]) is RECOMMENDED.
# 
# This timeout allows for multiple PTOs to expire prior to failing path
# validation, so that loss of a single PATH_CHALLENGE or PATH_RESPONSE
# frame does not cause path validation failure.
# 
# Note that the endpoint might receive packets containing other frames
# on the new path, but a PATH_RESPONSE frame with appropriate data is
# required for path validation to succeed.
# 
# When an endpoint abandons path validation, it determines that the
# path is unusable.  This does not necessarily imply a failure of the
# connection -- endpoints can continue sending packets over other paths
# as appropriate.  If no paths are available, an endpoint can wait for
# a new path to become available or close the connection.  An endpoint
# that has no valid network path to its peer MAY signal this using the
# NO_VIABLE_PATH connection error, noting that this is only possible if
# the network path exists but does not support the required MTU
# (Section 14).
# 
# A path validation might be abandoned for other reasons besides
# failure.  Primarily, this happens if a connection migration to a new
# path is initiated while a path validation on the old path is in
# progress.

[[spec]]
level = "SHOULD"
quote = '''
Endpoints SHOULD abandon path validation based on a timer.
'''

[[spec]]
level = "SHOULD"
quote = '''
A value of
three times the larger of the current PTO or the PTO for the new path
(using kInitialRtt, as defined in [QUIC-RECOVERY]) is RECOMMENDED.
'''

[[spec]]
level = "MAY"
quote = '''
An endpoint
that has no valid network path to its peer MAY signal this using the
NO_VIABLE_PATH connection error, noting that this is only possible if
the network path exists but does not support the required MTU
(Section 14).
'''