The current model document requires support for best-effort=false only.
But for the LPD-to-IPP gateway, IPP support for best-effort=true makes
things a whole lot easier because the gateway can translate LPD
functions to IPP attributes knowing that the attributes will not cause
the IPP operation to be rejected.
Without such support, the gateway must perform a Get-Attributes to find
out what the IPP printer supports and only send those attributes.
The attributes that the gateway needs to send are:
o job-name,
o job-sheets (standard or none),
o notification-events,
o notification-method,
o document-name and
o document-format.
All of these attributes, except job-name are optional, and none of them
affect the final output. So rejection of a job because of attribute
non-support would be very unfriendly.
So this is my concrete reason why all implementations must support
both values of best-effort and why it therefore should be a mandatory
parameter rather than a job-template attribute with a fixed set of values
that no client needs to query.
Bob Herriot