In the data transfer protocol,
the comment with variable rw that
"Always equals RW-nd+nr"
should be "Always equals RW-nr+nd".
The data transfer protocol in the note uses fixed-size data blocks.
An alternative is to send variable-sized data blocks.
This can be done by augmenting the data messages with
a field indicating the size of the data block.
Another alternative is to send a variable number of data blocks in a message.
If the data blocks are consecutive,
the message needs only identify the sequence number of the first data block
and the number of data blocks.
TCP does the latter with an octet, or byte, as the data block size.
A similar modification would be needed for selective and negative acks.
Figures 7,8,9 for the connection management protocol has errors
in that the Lin of a closed entity should be nil.
So change "w" to "nil", "u" to "nil",
"x>w" to "x greater than past values of client's Lin",
"y>u" to "y greater than past values of server's Lin".