Cisco Systems 6200 appendix What is the SLC 8DMT?, How the SLC 8DMT Handles Traffic

78-5296-02 10/02/98 Hardware Description 1

1.5.4 What is the SLC 8DMT?

The eight-port DMT version of the SLC (SLC 8DMT) is a hot-swappable line module that provides data communication between the Cisco 6200 node and up to eight subscribers. Modems on the SLC 8DMT use discrete multitone (DMT) modulation, a common method for encoding asymmetric digital subscriber line (ADSL) transmissions. The SLC 8DMT transmits high-speed data through an external POTS splitter to subscribers over existing, telephone-grade segments of copper wire. Figure 1-12 illustrates SLC operation.

Figure 1-12 SLC 8DMT Operation

ATM NTC

Cisco

6200

Cell filter

Contention

and

arbitration

Public

telephone

network

SLC

Port 1

POTS

DMTsplitter transceiver

POTS splitter

Port 2

Port 3

Port 8

ADSL

modem

13068

The SLC 8DMT transports data at speeds up to 8 Mbps downstream (from the service provider to the subscriber) and receives at speeds up to 800 kbps upstream (from the subscriber to the service provider). The SLC supports upstream and downstream passband channels for subscriber data.

Baseband plain old telephone service (POTS) is unused by the SLC; voice and data are added by the external POTS splitter.

How the SLC 8DMT Handles Traffic

In the downstream direction, the SLC receives ATM cells from the Cisco 6200 backplane bus. The cell filter discards cells whose virtual path/virtual channel IDs (VPI/VCIs) do not pertain to a particular subscriber’s channel. (Each port has a fixed set of 31 VCIs, numbered 33 to 63, which are permanently assigned to VCIs on the NTC.) The cell filter buffers cells, and the DMT transceiver transmits the outbound cells. The SLC sends the cells out to an external POTS splitter, which inserts baseband POTS traffic (if any such traffic is provided) before sending the downstream ADSL and POTS signals across standard unshielded twisted pair copper wire to the subscriber.

Cisco 6200 User Guide 1-27