This Recommendation document is Part 1 of a multi-part deliverable covering the Requirements for RF/IP switching system, as identified below: Part 1: Requirements; Part 2: Architecture and functional specifications; Cable television operators provide subscribers with a variety of video services composed of RF-signal-based video (RF-video) and IP-signal-based video (IP-video), e.g., linear and non-linear Video On Demand (VOD) over cable networks where the bandwidth is finite. Meanwhile, cable operators are facing the problem to correspond the 4K RF/IP video demands of subscribers while it is difficult to extend the network bandwidth due to the network cost. In general, with RF-video distribution scheme, the received video quality is stable since the video is distributed and received at a fixed coding bitrate over quality-guaranteed network where a fixed transmission bandwidth is reserved for each video. Utilization efficiency of cable networks is, however, low since the transmission bandwidths are occupied by the videos regardless audience ratings. In contrast, with the IP-video distribution scheme, the received video quality is unstable since the video is distributed and received at a variable or adaptive coding bitrate over best-effort network where a transmission bandwidth is not reserved for each video. Utilization efficiency of cable networks is, however, high since the transmission bandwidths are used for not only video but also Internet data according to subscribers' requests. For the response to the current situation, highly efficient cable transmission scheme that takes the advantages of both RF-video and IP-video distributions has been studied in order to maintain the received video quality and to improve the utilization efficiency of cable networks. The point is to share the RF and IP network bandwidth and to switch the distribution scheme adaptively between RF and IP according to the video content audience ratings, available network bandwidths, and attribute (e.g., emergency degree) of video content on cable headend (HE) side. On the receiver side, either RF-video or IP-video signals are received by turns, but seamlessly to form an uninterrupted video stream.