The basic video (IPTV) network model, shown in Figure 2, consists of up to five network elements.
Figure 2: Basic IPTV Network Model
These network elements are:
At the subscriber site, a set-top box links the television to the external network. This device initiates channel change requests and responds to status inquiries.
The routing gateway, often close to the subscriber site or a part of the set-top box, aggregates traffic from multiple subscribers and may act upon requests from the set-top box.
The digital subscriber line access multiplier (DSLAM), like the routing gateway, aggregates traffic from multiple subscribers and may act on requests from the set-top box. The DSLAM often resides at a separate, centrally located office.
Some networks can include an Ethernet switch or some other broadband services aggregator (BSA) to provide an additional layer of aggregation.
The edge router (typically a broadband services router [BSR] or video services router [VSR]) is the gateway into the backbone network. This device most often controls the multicast traffic to and channel requests from the set-top box.
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