Luminosity measurements at LHC.

In this article, we present the various techniques developed for measuring and monitoring the luminosity, both integrated than instantaneous, in p-p collisions at the LHC. The investigated methods range from old and new techniques for instantaneous luminosity measurement during dedicated runs, to the integrated luminosity evaluation via the total and differential forward elastic cross section measurement, to the offline-integrated measurement using known channels, and finally to the on-line techniques. A brief description of the detectors used for this purposes is given when needed.