  The International Linear Collider (ILC) is a future electron/positron
collider at the energy frontier. Its physics goals are clearly focused on
precision measurements at the electroweak scale and beyond. Beam energy and
beam polarisation are two important beam parameters, which need to be measured
and monitored to any possible precision. We discuss in this publication the
foreseen concepts of beam energy and beam polarisation measurement at the ILC:
Two Compton polarimeters per beam line will determine the beam polarisation.
The anticipated precision of this measurement amounts to $\Delta \mathcal{P} /
\mathcal{P} =2.5 \times 10^{-3}$, which is a challenging goal putting highest
demands on detector alignment and linearity. Recent detector developments as
well as a detector calibration technique are described, which allow for meeting
these requirements. The beam energy is measured before and after the
interaction point to a targeted precision of $\Delta E/E = 10^{-4}$. Thereby,
the two foreseen concepts are introduced: A noninvasive energy spectrometer
based on beam position monitors is planned to be operated before the
interaction region. Behind, a synchrotron radiation imaging detector will allow
not only for measuring the beam energy, but also gives access to the beam
energy spread of the (disrupted) beam.
