XML size on really big lans. I do not expect this to be used very often,
but it is handy. On the geni-lib side:

class setProperties(object):
    """Added to a Link or LAN object, this extension tells Emulab based
    clusters to set the symmetrical properties of the entire link/lan to
    the desired characteristics (bandwidth, latency, plr). This produces
    more efficient XML then setting a property on every source/destination
    pair, especially on a very large lan. Bandwidth is in Kbps, latency in
    milliseconds, plr a floating point number between 0 and 1. Use keyword
    based arguments, all arguments are optional:

        link.setProperties(bandwidth=100000, latency=10, plr=0.5)

    """