It is noteworthy that ETSI TISPAN specifies (next-generation network) NGN-based IPTV as "Multimedia system that provides IPTV services over the NGN architecture and may be implemented as an integrated subsystem with the NGN (NGN integrated IPTV) or may use the IMS subsystem (IMS-based IPTV) in the NGN".
ETSI TISPAN (European Telecommunications Standards Institute, Telecommunications and Internet converged Services and Protocols for Advanced Networking) is also conducting a relevant work on IPTV standardization.
Release 2 of specifications of TISPAN NGN adds new features and services to the NGN such as IPTV.
TISPAN release 2 defines three main services for the IMS-based IPTV system: (a) Broadcast TV; (b) Content on Demand (COD); and (c) Network-Personal Video Recorder (N-PVR).
Figure 4 shows an overview of the functional architecture defined by TISPAN for the IMS-based IPTV system in release 3 .
ETSI TISPAN specification for the IMS-based IPTV system and the NGN integrated IPTV system can be found in  and , respectively.
The specifications of Open IPTV Forum are partially based on TISPAN R2 specification for managed IPTV networks, but also specified IPTV for a non-managed networks (non-managed means without guarantee of QoS and Over Open Top--over Internet).
Hybrid scenarios may be supported also by TISPAN NGN integrated IPTV platform, while more information about hybrid scenarios in TISPAN is described in .
 ETSI TS 182 028 v3.5.1 (2011-02) Telecommunications and Internet converged Services and Protocols for Advanced Networking (TISPAN); NGN integrated IPTV subsystem Architecture.
 ETSI TS 183 064 V3.4.1 (2011-02) Telecommunications and Internet converged Services and Protocols for Advanced Networking (TISPAN); NGN integrated IPTV subsystem stage 3 specification
The major ones include: the 3rd Generation Partnership Project (3GPP) , European Telecommunications Standards Institute (ETSI) Telecommunications and Intemet Converged Services and Protocols for Advanced Networking European Telecommunications Standards Institute (TISPAN) , and the Telecommunication Standardization Sector of International Telecommunications Union (ITU-T) .
The proposed architecture is basically the same as the TISPAN architecture presented in Fig.