1. What means GDL and does it do ?
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GDL is a Group of DownLoads. A GDL allows to download one file from multiple
sources at the same time and is most of the time named segmented download.

The segmented download works even if the remote client is not an enhanced client.


2. How to use it ?
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basic knowledge: a GDL is defined by: 1) a gdl ID
                                      2) the local filename and its size
                                      3) 0 or more download source, each one
                                         defines a nickname, a remotefilename
                                         and a remote filesize.

* First, you must create a new GDL using /GDLNEW. Using it, you define at the
  same time, a gdl ID, a local filename and a file size. These values are set
  for the GDL whole life.

* Then, you must add one or more download sources to this GDL using /GDLADD.
  Using this command, you define a remote nickname, a remotefilename and a remote
  filesize.
  NOTE: the wanted size and the remote file sizes don't have to be the same. You
  can download segment of the file from source having truncated files.

* When all wanted bytes (from first position to wanted local size) are received,
  the segments are gathered to build the file and the GDL is destroyed.


3. Differences between /DL and /GDL*
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The main difference between segmented downloads (/GDL*) and normal downloads is
basically not the fact that one is segmented and the other is not. 

A normal download uses the queue list (CMDKB) shared by all running clients.Thus
it is possible to see a download moves from one hub to another just because the
transfer has been aborted and the remote user has gone to another hub (where 
another client is connected).

A segmented download uses it own list and each client has its list thus when a
segmented download is started, it will stay on its client ... until the end.

Note: since v0.79.0, normal download does not exist anymore.
