It has been observed that there is a strong spatial and temporal
locality in electricity demand. ITU Study Group 55 has studied this
phenomenon for over a decade and has issued a preliminary report.
This report states that when a lamp is turned on in one house, it is
usually the case that lamps are turned on in neighboring houses at
around the same time (usually at dusk) [3]. This observation has a
serious implication on the scalability of the signaling mechanism.
Specifically, the distribution network must be able to handle tens of
thousands of requests all at once. The signaling load can be reduced
if multicast delivery is used. Briefly, a request for electricity is
not sent from the lamp all the way to an ES, but is handled by the
first LSR that is already in the path to another lamp.
Support for this requires the application of multicast routing
protocols together with RSVP-TE shared reservation styles and the
development of MPLampS multicast forwarding mode. We are currently
studying the following multicast routing protocol:
o DVMRP: Discrete Voltage Multicast Routing Protocol - this protocol
works over existing voltage routing protocols but the danger here is
that electricity is delivered to all lamps when any one lamp is
turned on. Indeed, the switching semantics gets annoying - all lamps
get turned on periodically and those not needed must be switched off
each time manually.
Other protocols we will eventually consider are Current-Based Tree
(CBT) and Practically Irrelevant Multicast (PIM). An issue we are
greatly interested in is multicast scope: we would like support for
distributing electricity with varying scope, from lamps within a
single Christmas tree to those in entire cities. Needless to say, we
will write many detailed documents on these topics as time
progresses.
