venues from such services using the given network capacity. Let's make the simple calculation for the required capacity between network nodes A and B, which are multicast capable routers in this second case (in the first case here they were only unicast capable routers). Multicast needs only one copy of each IP packet to be delivered (from each of the 100 TV channels), which gives required capac- ity of 100 X 3 Mbit/s = 3 Gbit/s for all SDTV channels, and 100 X 6 Mbit/s = 600 Mbit/s for all HDTV channels (Figure 6.4). So, with multicast, the required network capacity is significantly lower (for a large number of IPTV customers, which is a typical case for having a sustainable IPTV business) and it is dependent upon the number of TV 6.2 QoS-enabled Video and IPTV Services IPTV streaming Example: 100 IPTV streams servers Example: Transfer of 100 IPTV streams with multicast routing Multicast tree IPTV service root router provider Access network Access network gateway gateway Network provider Unicast IPTV (e.g. QoS with streams (e.g. one MPLS/DiffServ) stream to one STB) Unicast IPTV streams gateway gateway Home LAN Home LAN (e.g. Ethernet) (e.g. Ethernet) DiffServ - Differentiated services LAN - Local area network MPLS - Multi-protocol label switching STB - Set top box Figure 6.4 QoS provisioning for IPTV and QoS-enabled video services. channels being offered to the end customers (which is a fixed number in a given period of time, and hence provides easier network dimensioning and planning) and it is not dependent upon the number of customers. So, with multicast usage in the transport and core IP networks for IPTV, QoS can be guaranteed for end-users. There are several different multicast protocols standardized by the IETF [2]; however, not all of them are being used equally. Multicast is based on the creation of multicast groups and usage of multicast routing protocols. For this purpose the creation of the multicast groups in IPv4 networks is done with IGMP (Internet Group Management Protocol), which is standardize