STANDARD Revision 1.0 C4® CMTS Release 8.3 User Guide
© 2016 ARRIS Enterprises LLC. All Rights Reserved. 616
Chapter 19
DOCSIS Set-top Gateway Configuration
Overview .......................................................................................... 616
DSG 3.0 ............................................................................................. 619
DSG Configuration Overview ............................................................ 622
Sample DSG Configuration Scenarios ............................................... 637
Overview
Many Multiple System Operators (MSOs) are using DOCSIS to transport Digital Video Out-of-Band (OOB) data, including
Conditional Access, Service Information, Electronic Program Guide, Emergency Alert System, and more. In the DSG
Architecture OOB data is transported from the DSG servers within the MSO’s Set-top Controllers through the DSG Agents
residing on the CMTSs, to the DSG Clients within Set-top Devices.
Logical Devices in a DSG System
This OOB data traverses the DSG Agent on the CMTS by means of a DSG Tunnel — a non-encapsulated, rate-limited data
flow that is MAC multicasted on one or more DOCSIS downstream channels. Because it is non-encapsulated, it is not a
tunnel in the traditional form. The DSG Agent is responsible for forwarding IP datagrams that make up a DSG tunnel, rate
limiting or shaping the DSG Tunnel, and sending DSG Tunnel advertisements (as DCD messages) at a rate of least one per
second. Due to the multicast nature of the DSG tunnel traffic, multicast routing protocols such as PIM-SSM and IGMPv3 are
used by the DSG agent to subscribe to the multicast groups containing the OOB data. DSIDs are included with each IP
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