  An attractive new feature of connected TV systems consists in allowing users
to access past portions of the TV channel. This feature, called time-shifted
streaming, is now used by millions of TV viewers. We address in this paper the
design of a large-scale delivery system for time-shifted streaming. We
highlight the characteristics of time-shifted streaming that prevent known
video delivery systems to be used. Then, we present two proposals that meet the
demand for two radically different types of TV operator. First, the
Peer-Assisted Catch-Up Streaming system, namely PACUS, aims at reducing the
load on the server of a large TV broadcasters without losing the control of the
TV delivery. Second, the turntable structure, is an overlay of nodes that allow
an independent content delivery network or a small independent TV broadcaster
to ensure that all past TV programs are stored and as available as possible. We
show through extensive simulations that our objectives are reached, with a
reduction of up to three quarters of the traffic for PACUS and a 100\%
guaranteed availability for the turntable structure. We also compare our
proposals to the main previous works in the area.
