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A DOCSIS SET-TOP GATEWAY CHANNEL AUTO SELECTION METHOD IN A CABLE MODEM TERMINAL SYSTEM

IP.com Disclosure Number: IPCOM000241605D
Publication Date: 2015-May-15
Document File: 4 page(s) / 79K

Publishing Venue

The IP.com Prior Art Database

Related People

Jianjun Hu: AUTHOR [+4]

Abstract

A solution is provided for a dynamic algorithm to minimize downstream DOCSIS Set-Top Gateway (DSG) traffic so as to have no impact on other services in a DOCSIS system. This allows a broadband router to support more DSG classifiers for a customer, saves downstream bandwidth and multicast forwarding resources, and frees up resources for Video over DOCSIS (VDOC) services and other features and services.

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A DOCSIS SET-TOP GATEWAY CHANNEL AUTO SELECTION METHOD IN A CABLE MODEM TERMINAL SYSTEM

AUTHORS:

 Jianjun Hu Zhizhou Li Wenwen Dong

Jie Ren

CISCO SYSTEMS, INC.

ABSTRACT

    A solution is provided for a dynamic algorithm to minimize downstream DOCSIS Set-Top Gateway (DSG) traffic so as to have no impact on other services in a DOCSIS system. This allows a broadband router to support more DSG classifiers for a customer, saves downstream bandwidth and multicast forwarding resources, and frees up resources for Video over DOCSIS (VDOC) services and other features and services.

DETAILED DESCRIPTION

     In a cable modem termination system (CMTS), the DOCSIS Set-Top Gateway (DSG) feature is an extension of the DOCSIS protocol. The DOCSIS protocol is a specification describing how out-of-band data is delivered to a cable set-top box. Cable set-top boxes need a reliable source of out-of-band data for information such as program guides, channel lineups, and updated code images. In order to forward DSG traffic to every set-top gateway, the CMTS system uses a multicast mechanism to forward the traffic to every primary channel which is configured as a DSG channel. Though the multicast traffic can be shared efficiently in one channel, the CMTS system still needs to replicate packets for every multicast channel, which will be the bottleneck of the CMTS forwarding system because the number of packets grows with the number of the forwarding channels. This problem does not have any impact if the scale of the system is small, but it has a great impact in the Converged Cable Access Platform (CCAP) system which offers much greater scalability and higher-density than previous systems. This is because with the growth of the packets and number of channels, the number of packets

Copyright 2015 Cisco Systems, Inc.
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needed to be replicated will grow much faster, which will quickly exhaust the resources in the CMTS forwarding engine.

    For example, consider a typical configuration in a Cisco Converged Broadband Router (cBR8): 10 (Classifiers (CFRs)) * 32(primary channel per Media Access Control (MAC) Domain (MD)) * 16 (MD per Line Cards (LCs)) * 8 (LC per chassis) = 40960 multicast session per chassis, but the router only supports 20K multicast sessions. Each bit of DSG traffic means 4096 replications for the packet processor, Max 2Mbps DSG...