Community-Lab introduction

Modified script.txt from [9c33eb68e0] to [daf35fb5e3].

    39     39   - Also nodes in participating research centres.
    40     40   - Linked together over the FEDERICA academic backbone.
    41     41   - All its software and documentation is released under Free licenses, anyone
    42     42     can setup a CONFINE testbed like Community-Lab.
    43     43   
    44     44   * Challenges and requirements
    45     45   ** Simple management vs. Distributed node ownership
    46         -- In contrast with e.g. indoors testbeds that belong wholly to the same
    47         -  entity.
           46  +- How to manage devices belonging to diverse owners.
    48     47   
    49     48   ** Features vs. Lightweight, low cost (free & open)
    50     49   - Devices ranging from PCs to embedded boards.
    51     50   - Need light system able to run on very different devices.
    52     51   
           52  +** Heterogeneity vs. Compatibility
           53  +- Some devices allow hacking while others don't.
           54  +- Diverse connectivity and link technologies (wireless, wired, fiber).
           55  +
    53     56   ** Familiarity & flexibility vs. System stability
    54         -- Familiar Linux env with root access to researchers.
    55         -- Keep env isolation (nodes are shared by experiments).
    56         -- Keep node stability (to avoid in-place maintenance, some difficult to reach
    57         -  node locations).
           57  +- Researchers prefer a familiar Linux env with root access.
           58  +- But experiments sharing the same node must be isolated.
    58     59   # Frozen tower.
           60  +- Accessing node locations can be hard, so keep node stability to avoid
           61  +  in-place maintenance.
    59     62   
    60     63   ** Flexibility vs. Network stability
    61     64   - Network experiments running on nodes in a production network.
    62         -- Allow interaction with CN at the lowest level possible but not disrupting or
    63         -  overusing it.
           65  +- Allow interaction at the lowest possible layer of the CN while not
           66  +  disrupting or overusing it.
    64     67   
    65     68   ** Traffic collection vs. Privacy of CN users
    66     69   - Experiments performing traffic collection and characterization.
    67     70   - Avoid researchers spying on users' data.
    68     71   
    69     72   ** Link instability vs. Management robustness
    70         -- Deal with frequent network outages in the CN.
           73  +- Management must deal with frequent network outages in the CN.
    71     74   
    72     75   ** Reachability vs. IP address provisioning
    73     76   - Testbed spanning different CNs.
    74     77   - IPv4 scarcity and incompatibility between CNs, lack of IPv6 support.
    75     78   
    76         -** Heterogeneity vs. Compatibility
    77         -- Lots of different devices (disparate connectivity and software openness).
    78         -- Lots of different link technologies (wireless, wired, fiber).
    79         -
    80     79   * Community-Lab testbed architecture
    81     80   ** Overall architecture
    82     81   This architecture applies to all testbeds using the CONFINE software.
    83     82   # Move over overlay diagram less overlay connections plus overlay network.
    84     83   - A testbed consists of a set of nodes managed by the same server.
    85     84     - Server managed by testbed admins.
    86     85     - Network and node managed by node admins (usually owners and CN members).