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19.1.2 Session and Subsession
Subsession
One Parameter Set can be transferred per subsession. Subsession transfers one Parameter Set or data that is broken
down into multiple packets for transfer, with EOD (End of data) sent at the end to terminate the send.
Data is broken down into multiple packets when a single Parameter Set is larger than a certain size. The Packet
Number in the packet's index field is used to indicate the sequential position of a packet relative to the other
packets. Even if Parameter Sets are small, they cannot be grouped together and sent as a single packet. A
Parameter Set delimiter is always treated as a packet delimiter for transfer.
Session
One Parameter Set or multiple Parameter Sets can be transferred by one session. A session can consist of one
subsession or multiple subsessions, with EOS (End of session) sent at the end to terminate the send. Regardless of
whether there is a single Parameter Set or multiple Parameter sets, an actual bulk dump always takes the form of
a session, never a subsession only.
19.2 One-way Protocol Communication Flow
A session starts with the receiving device sending a request using a BDR, or with the sending device sending
BDS data. The session ends after transfer of all the data in the parameter set being transferred by the sending
device is complete.
Data is divided into multiple packets of 256 bytes or less each, and transfers them at fixed intervals (20 msec).
A final EOD informs the receiving device when the session is ended.
Data Receiver Data Sender Operation
BDR → Send Request (Optional)
← BDS Data Transfer
(20 msec or greater interval)
← BDS Data Transfer
(20 msec or greater interval)
← BDS Data Transfer
(20 msec or greater interval)
:
:
← EOD Data End
:
Other subsessions
:
← EOS End of session