Cisco 6200 User Manual

Page 14

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Hardware Description

78-5296-02

10/02/98

Cisco 6200 User Guide

1-14

The NTC STM-1 also transmits upstream data back to the service provider via ATM on the STM-1
physical layer.

The Cisco 6200 uses a fixed mapping of permanent virtual channels (PVCs) between trunk and
subscriber ports. This means that no configuration of these circuits is required. Thirty-one PVCs link
each subscriber port to the trunk port on the NTC. These subscriber traffic PVCs are assigned virtual
channel identifiers (VCIs) 33 through 63. VCIs 0 through 31 are reserved for control traffic. All of
these VCs use virtual path identifier (VPI) 0. See the Cisco 6200 User Guide for instructions on
using the command show dsl vcmap to display the VCIs assigned to a particular slot or port.

The NTC STM-1 collects ATM cell counts, which are accessible through the 6200 Management
Information Base (MIB). These cell count include:

Number of nonidle cells transmitted upstream

Number of nonidle downstream cells received with good or correctable header checksums

Number of downstream cells received with uncorrectable header checksums

The NTC STM-1 provides bidirectional adaptation between serial ATM cells within the STM-1 fiber
and the 16-bit-parallel format on the backplane’s 160-Mbps H-bus. Three basic circuits perform this
adaptation process:

Optical interface

Upstream data transfer

Downstream data transfer

Figure 1-7 shows how the three circuits interact.

Figure 1-7

NTC STM-1 Application

The optical interface performs the optical-to-electrical and electrical-to-optical conversions. Its
other tasks include clock recovery, cell delineation, and diagnostic information retrieval.

Cisco

6200

NTC

14270

ATM on

STM-1

Optical

interface

Downstream

data

transfer

Upstream

data

transfer

Line

module

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