Bernd Schloer raised the concern of eliminating <M> in his message referenced above:
"In version 13 of the QSPEC-draft the Maximum Packet Size [M] was removed from the TMOD parameter (former Traffic parameter).
RFC2211 mentions, that links are not permitted to fragment packets which receive the controlled-load service and packets larger than the MTU of the link are treated as non-conformant to the TSPEC.
[note: see RFC 4821 http://www.rfc-editor.org/rfc/rfc4821.txt
as a replacement for specifying M, Max Pkt size:
- only the sending end-point will store what PLPMTUD discovers,
intermediate points where shaping or policing reside will not
know the Max pkt size the sender intends to use.
- the Max packet size that a sender uses may be much less than MTU,
VoIP is the most obvious example.
Or, it wasn't understood that M was a critical part of the peak
rate definition. From RFC 2212:
The peak rate, p, is measured in bytes of IP datagrams per second and
has the same range and suggested representation as the bucket rate.
The peak rate is the maximum rate
at which the source and any
reshaping points (reshaping points are defined below) may inject
bursts of traffic into the network. More precisely, it is a
requirement that for all time periods the amount of data sent cannot
exceed M+pT where M is the maximum datagram size and T is the length
of the time period.
Note that parameter M is part of the RFC 2212 TSPEC, and M is apparently
different from the MTU:
Links are not permitted to fragment datagrams as part of guaranteed
service. Datagrams larger than the MTU of the link MUST be policed
as non-conformant which means that they will be policed according to
the rules described in the Policing section below."