Cisco Systems MC-607 manual Operating Modes, MC-611

Configuring Subscriber-End Broadband Access Router Features

Subscriber-End Broadband Access Router Data Operations

Note End-to-end throughput varies based on the design and loading of network components, the mix of traffic, the processing speed and interface of the host server(s), the processing speed and local Ethernet performance of the subscriber computer, and other parameters. Because the network can be configured to support multiple levels of service to meet differing market price/performance requirements, the subscriber service-level agreement also affects throughput. DOCSIS further contains some fundamental performance limitations because standards are designed to give a larger number of customers good performance, rather than permitting a few users to consume the entire capacity.

Figure 110 Typical Cisco Broadband Data Cable System

WAN

Switch/router

	Combiner	Tx
CMTS
rack equipment		Rx

Fiber

Servers

Cisco uBR900 series cable access router

Internal backbone

and

worldwide internet

HFC

cable plant

Cable System Headend

Upstream and downstream data interfaces Operation support system interface Downstream RF interface

Upstream RF interface

18197

Residence or SOHO subscriber site: subscriber RF interface Ethernet interface

Operating Modes

The broadband data cable system uses multiple types of access control to ensure efficient use of bandwidth over a wide range of loading conditions. Advanced queueing techniques and service algorithms are used to define the acquisition and release of channels.

Cisco uBR900 series cable access routers support 64 or 256 Quadrature Amplitude Modulation (QAM) downstream, and Quadrature Phase Shift Keying (QPSK) or 16 QAM upstream transmission. The CMTS system administrator can set the preferred modulation scheme based on the quality of the cable plant.

Note In noisy plant environments, 16 QAM upstream and 256 QAM downstream modulation may not be viable. In high-quality HFC networks capable of supporting 16 QAM formats in the upstream direction, we recommend using QPSK for fixed-slot short packets like maintenance or data requests, and 16 QAM for variable-length data packets. This results in the most efficient use of the available upstream timeslots or minislots.

Cisco IOS Multiservice Applications Configuration Guide

MC-611