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Printable Version: RFC2204.PDF
RFC 2204 ODETTE File Transfer Protocol September 1997
Speaker -- EERP ------------> Listener End to End Response
<------------- RTR -- Ready to Receive
-- EERP ------------> End to End Response
<------------- RTR -- Ready to Receive
-- SFID ------------> Start File
or
-- CD --------------> Exchange the turn
After sending an EERP, the Speaker must wait for an RTR before
sending any other commands.
4.4 Data Transfer Phase
Virtual File data flows from the Speaker to the Listener during the
Data Transfer phase which is entered after the Start File phase.
4.4.1 Protocol Sequence
To avoid congestion at the protocol level a flow control mechanism is
provided via the Credit (CDT) command.
A Credit limit is negotiated in the Start Session phase, this
represents the number of Data Exchange Buffers that the Speaker may
send before it is obliged to wait for a Credit command from the
Listener.
The available credit is initially set to the negotiated value by the
Start File positive answer, which acts as an implicit Credit command.
The Speaker decreases the available credit count by one for each data
buffer sent to the Listener.
When the available credit is exhausted, the Speaker must wait for a
Credit command from the Listener otherwise a protocol error will
occur and the session will be aborted.
The Listener should endeavour to send the Credit command without
delay to prevent the Speaker blocking.
1. Speaker -- SFID ------------> Listener Start File
<------------ SFPA -- Answer YES
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