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Transport aspects 2

Figure 5-3 – Reference model of NT-n

The data plane information flow over the γR reference point is represented by a single downstream data
stream (STREAMds-n) and a single upstream data stream (STREAMus-n). The FTU-R may use flow control
(TX Enable-n) on the upstream data steam. The ME conveys the management information (over an
interface here called γ_MGMTR) to the FTU-R.

The TCE receives NTR and ToD over the network frequency/timing from the FTU-R over the γR reference
point, and passes the network frequency/timing to the PHY and the L2+ block so as to provide network
frequency/timing at the T reference point (e.g., 1PPS [b-IEEE1588]). Inside the NT-n, the ME conveys the
management information (over an interface here called TCE-m) to the TCE.
The DRA related primitives (see Table 8-4) are represented by DRRus, LinkState, and battery operation
(BAT) crossing the γR reference point. The DRRus primitive is for the FTU-R to receive the DRR from the L2+
(and to send/receive DRR configuration to/from the L2+). The LinkState primitive is for the FTU-R to
indicate the link state to the ME. The battery-operation (BAT) primitive is for the PSE (if internal to the NT)
to indicate the battery operation to the FTU-R. The PSE also indicates the battery operation to the ME over
the PSE-m interface.

5.2 Application reference models
Implementations complying with this Recommendation are typically deployed in a fibre to the-distribution
point (FTTdp) scenario. A FTTdp deployment may be a further evolution of a FTTx (e.g., FTTCabinet,
FTTBuilding and FTTcurb) deployment, taking the fibre deeper into the network, or it may be a FTTH
deployment with a copper extension where installation of the fibre inside the customer premises is not
possible. The optical distribution network that feeds the distribution point units (DPUs) may be based on
point-to-multipoint (e.g., PON) or point-to-point (e.g., GbE) technologies.

A key aspect of FTTdp deployment is the requirement that the customer should be able to self-install the
equipment. Figure 5-4 provides an overview of the basic application reference model for customer self-
install with POTS as the underlying narrowband service. Alternatively, the integrated services digital
network (ISDN) may be used as the underlying narrowband service. This application model is very similar to

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