Class FRAG2


  • public class FRAG2
    extends Protocol
    Fragmentation layer. Fragments messages larger than frag_size into smaller packets. Reassembles fragmented packets into bigger ones. The fragmentation number is prepended to the messages as a header (and removed at the receiving side).

    Each fragment is identified by (a) the sender (part of the message to which the header is appended), (b) the fragmentation ID (which is unique per FRAG2 layer (monotonically increasing) and (c) the fragement ID which ranges from 0 to number_of_fragments-1.

    Requirement: lossless delivery (e.g. NAK, ACK). No requirement on ordering. Works for both unicast and multicast messages.
    Compared to FRAG, this protocol does not need to serialize the message in order to break it into smaller fragments: it looks only at the message's buffer, which is a byte[] array anyway. We assume that the size addition for headers and src and dest address is minimal when the transport finally has to serialize the message, so we add a constant (200 bytes).

    Version:
    $Id: FRAG2.java,v 1.36.2.1 2008/07/22 11:51:22 belaban Exp $
    Author:
    Bela Ban
    • Constructor Detail

      • FRAG2

        public FRAG2()
    • Method Detail

      • getName

        public final java.lang.String getName()
        Specified by:
        getName in class Protocol
      • getFragSize

        public int getFragSize()
      • setFragSize

        public void setFragSize​(int s)
      • getOverhead

        public int getOverhead()
      • setOverhead

        public void setOverhead​(int o)
      • getNumberOfSentMessages

        public long getNumberOfSentMessages()
      • getNumberOfSentFragments

        public long getNumberOfSentFragments()
      • getNumberOfReceivedMessages

        public long getNumberOfReceivedMessages()
      • getNumberOfReceivedFragments

        public long getNumberOfReceivedFragments()
      • setProperties

        public boolean setProperties​(java.util.Properties props)
        Setup the Protocol instance acording to the configuration string
        Overrides:
        setProperties in class Protocol
      • init

        public void init()
                  throws java.lang.Exception
        Description copied from class: Protocol
        Called after instance has been created (null constructor) and before protocol is started. Properties are already set. Other protocols are not yet connected and events cannot yet be sent.
        Overrides:
        init in class Protocol
        Throws:
        java.lang.Exception - Thrown if protocol cannot be initialized successfully. This will cause the ProtocolStack to fail, so the channel constructor will throw an exception
      • down

        public java.lang.Object down​(Event evt)
        Fragment a packet if larger than frag_size (add a header). Otherwise just pass down. Only add a header if framentation is needed !
        Overrides:
        down in class Protocol
      • up

        public java.lang.Object up​(Event evt)
        If event is a message, if it is fragmented, re-assemble fragments into big message and pass up the stack.
        Overrides:
        up in class Protocol