Packet writing.
  Allows for multiple writes to a single track or session. 

  Used for data only - mode 1 and mode 2 XA.

  Requires support of UDF. Universal Disk format
    Originally an add-on driver but available in latest Windows XP(?).
    Available on several OSes (but not all features).

    UDF (ISO/IEC 13346) replaces ISO 9660 
      Open vendor neutral file-system protocol.
      Several revisions exist. 1.02, 1.50, 2.00, 2.01, 2.50, 2.60

  Initially for CD-RWs but can work on CD-Rs and common for DVD-r (1.02).
    However, only readable by another machine that recognizes UDF version.

  Also may be used by flash and some newer hard drives.

  Packets also use lead-in/lead-out but much smaller.

  Packet writing allows more writes than track level.
     Lead-ins and lead-outs much smaller at packet level than track level.
     However, each write requires a lead-in and lead-out, so total lead-in
       lead-out space may be greater for packet writing.

  UDF is supposed to be independent of the OS being used. However, the newer
    releases of UDF are only supported by the latest OSes. And a disk burned
    with a newer version of UDF may not be accessible on an older system.

  In general, UDF fully supported by, Vista, Windows 7, Linux 2.6, 
    Mac OSX 10.5, NetBSD 5