target = "https://www.rfc-editor.org/rfc/rfc9000#section-19.3.1"

# 19.3.1.  ACK Ranges
#
# Each ACK Range consists of alternating Gap and ACK Range Length
# values in descending packet number order.  ACK Ranges can be
# repeated.  The number of Gap and ACK Range Length values is
# determined by the ACK Range Count field; one of each value is present
# for each value in the ACK Range Count field.
# 
# ACK Ranges are structured as shown in Figure 26.
# 
# ACK Range {
#   Gap (i),
#   ACK Range Length (i),
# }
# 
#                         Figure 26: ACK Ranges
# 
# The fields that form each ACK Range are:
# 
# Gap:  A variable-length integer indicating the number of contiguous
#    unacknowledged packets preceding the packet number one lower than
#    the smallest in the preceding ACK Range.
# 
# ACK Range Length:  A variable-length integer indicating the number of
#    contiguous acknowledged packets preceding the largest packet
#    number, as determined by the preceding Gap.
# 
# Gap and ACK Range Length values use a relative integer encoding for
# efficiency.  Though each encoded value is positive, the values are
# subtracted, so that each ACK Range describes progressively lower-
# numbered packets.
# 
# Each ACK Range acknowledges a contiguous range of packets by
# indicating the number of acknowledged packets that precede the
# largest packet number in that range.  A value of 0 indicates that
# only the largest packet number is acknowledged.  Larger ACK Range
# values indicate a larger range, with corresponding lower values for
# the smallest packet number in the range.  Thus, given a largest
# packet number for the range, the smallest value is determined by the
# following formula:
# 
#    smallest = largest - ack_range
# 
# An ACK Range acknowledges all packets between the smallest packet
# number and the largest, inclusive.
# 
# The largest value for an ACK Range is determined by cumulatively
# subtracting the size of all preceding ACK Range Lengths and Gaps.
# 
# Each Gap indicates a range of packets that are not being
# acknowledged.  The number of packets in the gap is one higher than
# the encoded value of the Gap field.
# 
# The value of the Gap field establishes the largest packet number
# value for the subsequent ACK Range using the following formula:
# 
#    largest = previous_smallest - gap - 2
# 
# If any computed packet number is negative, an endpoint MUST generate
# a connection error of type FRAME_ENCODING_ERROR.

[[spec]]
level = "MUST"
quote = '''
If any computed packet number is negative, an endpoint MUST generate
a connection error of type FRAME_ENCODING_ERROR.
'''