[FE] Pascal issue
The way maxEnvelopSize has been integrated into the Pascal, appears to make support for the envelope frame size mandatory for all implementations.
maxValidFrame should be defined to be an implementation option between three choices -
maxBasicFrameSize
maxBasicFrameSize + qTagPrefixSize
maxEnvelopeFrameSize
I also think that "implementation dependent" for maxBasicFrameSize and maxEnvelopeFrameSize has become misleading given that we only allow one size in the table. Also usually when we say that we mean the implementor can choose a value. "Technology dependent" would be more accurate. This implies a change to the title of 4.4 as well.