target = "https://www.rfc-editor.org/rfc/rfc9002#section-6.1.2"

# 6.1.2.  Time Threshold
#
# Once a later packet within the same packet number space has been
# acknowledged, an endpoint SHOULD declare an earlier packet lost if it
# was sent a threshold amount of time in the past.  To avoid declaring
# packets as lost too early, this time threshold MUST be set to at
# least the local timer granularity, as indicated by the kGranularity
# constant.  The time threshold is:
# 
# max(kTimeThreshold * max(smoothed_rtt, latest_rtt), kGranularity)
# 
# If packets sent prior to the largest acknowledged packet cannot yet
# be declared lost, then a timer SHOULD be set for the remaining time.
# 
# Using max(smoothed_rtt, latest_rtt) protects from the two following
# cases:
# 
# *  the latest RTT sample is lower than the smoothed RTT, perhaps due
#    to reordering where the acknowledgment encountered a shorter path;
# 
# *  the latest RTT sample is higher than the smoothed RTT, perhaps due
#    to a sustained increase in the actual RTT, but the smoothed RTT
#    has not yet caught up.
# 
# The RECOMMENDED time threshold (kTimeThreshold), expressed as an RTT
# multiplier, is 9/8.  The RECOMMENDED value of the timer granularity
# (kGranularity) is 1 millisecond.
# 
#    |  Note: TCP's RACK [RFC8985] specifies a slightly larger
#    |  threshold, equivalent to 5/4, for a similar purpose.
#    |  Experience with QUIC shows that 9/8 works well.
# 
# Implementations MAY experiment with absolute thresholds, thresholds
# from previous connections, adaptive thresholds, or the including of
# RTT variation.  Smaller thresholds reduce reordering resilience and
# increase spurious retransmissions, and larger thresholds increase
# loss detection delay.

[[spec]]
level = "SHOULD"
quote = '''
Once a later packet within the same packet number space has been
acknowledged, an endpoint SHOULD declare an earlier packet lost if it
was sent a threshold amount of time in the past.
'''

[[spec]]
level = "MUST"
quote = '''
To avoid declaring
packets as lost too early, this time threshold MUST be set to at
least the local timer granularity, as indicated by the kGranularity
constant.
'''

[[spec]]
level = "SHOULD"
quote = '''
If packets sent prior to the largest acknowledged packet cannot yet
be declared lost, then a timer SHOULD be set for the remaining time.
'''

[[spec]]
level = "SHOULD"
quote = '''
The RECOMMENDED time threshold (kTimeThreshold), expressed as an RTT
multiplier, is 9/8.
'''

[[spec]]
level = "SHOULD"
quote = '''
The RECOMMENDED value of the timer granularity
(kGranularity) is 1 millisecond.
'''

[[spec]]
level = "MAY"
quote = '''
Implementations MAY experiment with absolute thresholds, thresholds
from previous connections, adaptive thresholds, or the including of
RTT variation.
'''