target = "https://www.rfc-editor.org/rfc/rfc8899#section-4.4"

# 4.4.  The Maximum Packet Size (MPS)
#
# The result of probing determines a usable PLPMTU, which is used to
# set the MPS used by the application.  The MPS is smaller than the
# PLPMTU because it is reduced by the size of PL headers (including the
# overhead of security-related fields such as an AEAD tag and TLS
# record layer padding).  The relationship between the MPS and the
# PLPMTUD is illustrated in Figure 1.
# 
# Any additional
#   headers         .--- MPS -----.
#          |        |             |
#          v        v             v
#   +------------------------------+
#   | IP | ** | PL | protocol data |
#   +------------------------------+
# 
#              <----- PLPMTU ----->
#   <---------- PMTU -------------->
# 
#             Figure 1: Relationship between MPS and PLPMTU
# 
# A PL is unable to send a packet (other than a probe packet) with a
# size larger than the current PLPMTU at the network layer.  To avoid
# this, a PL MAY be designed to segment data blocks larger than the MPS
# into multiple datagrams.
# 
# DPLPMTUD seeks to avoid IP fragmentation.  An attempt to send a data
# block larger than the MPS will therefore fail if a PL is unable to
# segment data.  To determine the largest data block that can be sent,
# a PL SHOULD provide applications with a primitive that returns the
# MPS, derived from the current PLPMTU.
# 
# If DPLPMTUD results in a change to the MPS, the application needs to
# adapt to the new MPS.  A particular case can arise when packets have
# been sent with a size less than the MPS and the PLPMTU was
# subsequently reduced.  If these packets are lost, the PL MAY segment
# the data using the new MPS.  If a PL is unable to resegment a
# previously sent datagram (e.g., [RFC4960]), then the sender either
# discards the datagram or could perform retransmission using network-
# layer fragmentation to form multiple IP packets not larger than the
# PLPMTU.  For IPv4, the use of endpoint fragmentation by the sender is
# preferred over clearing the DF bit in the IPv4 header.  Operational
# experience reveals that IP fragmentation can reduce the reliability
# of Internet communication [RFC8900], which may reduce the probability
# of successful retransmission.

[[spec]]
level = "MAY"
quote = '''
To avoid
this, a PL MAY be designed to segment data blocks larger than the MPS
into multiple datagrams.
'''

[[spec]]
level = "SHOULD"
quote = '''
To determine the largest data block that can be sent,
a PL SHOULD provide applications with a primitive that returns the
MPS, derived from the current PLPMTU.
'''

[[spec]]
level = "MAY"
quote = '''
If these packets are lost, the PL MAY segment
the data using the new MPS.
'''