flowcontrol.java

JXTA&#8482 is a set of open, generalized peer-to-peer (P2P) protocols that allow any networked devi

/*
 * Copyright (c) 2003-2007 Sun Microsystems, Inc.  All rights reserved.
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 *     developed by Sun Microsystems, Inc. for JXTA(TM) technology." 
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package net.jxta.impl.util.pipe.reliable;


/**
 * A basis for any flow control module to be plugged into
 * ReliableOutputStream.  Synchronization can is assumed to be
 * provided externaly. However all implementations are required to
 * allow the getRwindow() method to be called at any time without
 * synchronization.
 */

public abstract class FlowControl {

    /**
     * Returns the rwindow size that this flow control module suggests to use
     * at this point in time.
     * @return the remote window size
     */
    public abstract int getRwindow();

    /**
     * Indicates that a new ack message is being processed.
     */
    public void ackEventBegin() {}

    /**
     * Invoked for each packet that is believed to have been received
     * per the current ack message.
     *
     * @param seqnum The sequence number of the received packet.
     */
    public void packetACKed(int seqnum) {}

    /**
     * Invoked for each packet that is believed to have been lost
     * per the current ack message.
     *
     * @param seqnum The sequence number of the missing packet.
     */
    public void packetMissing(int seqnum) {}

    /**
     * Concludes rwindow update for this ackEvent. That's where all the
     * smarts are. A number of externally computed parameters must be
     * passed.
     *
     * @param rQSize the last known value of the remote queue size.
     * @param aveRTT the latest estimate of the average RTT.
     * @param lastRTT the RTT inferred from the most recent ACK message.
     * @return int the new recommended value for rwindow.
     */

    public abstract int ackEventEnd(int rQSize, long aveRTT, long lastRTT);
}