This information explains the fields in a Broadcast Data (BDATA)
Packet in detail.
- block#
- 2–byte binary number in the network byte order that indicates the number
of a particular block of data.
- sbid
- 4–byte binary number in the network byte order that is called the subnet
broadcast identification. This must be compared with the sbid that
was returned in the OACK response to a read request (RRQ) with the Subnet
Broadcast option. Along with the source port, this uniquely identifies a Subnet
Broadcast File Transfer. The source port of the BDATA packet must be compared
with the source port of the initial OACK packet that was received for this
transfer. Only BDATA packets that match on both the SBID and source ports
are considered part of the requested transfer. All other BDATA packets must
be ignored.
- data
- This is the data for this block of the file transfer. With the exception
of the last block of the file, the size of the data is equal to the block
size for the transfer. The last block of the file must be less than the block
size, even if it means that the length of the data in the last block is zero.
However, the server might not be done broadcasting blocks after the last block
of the file is broadcast. Control can be transferred to another client in
the subnet broadcast file group that has not yet received all the blocks in
the file.