Cisco Headend System Release 2.7 Design Guide

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DNCS Configuration for SFM 
4012166 Rev B 
 
The DHCT does not have prior knowledge of the DSG tunnel address when it is 
searching for the appropriate DOCSIS downstream. Instead, the DHCT parses the 
DCD message and determines which, if any, Cisco DSG clients (client IDs) are listed 
in the DCD message. If the required client IDs are listed in the DCD message, the 
DHCT will remain on the DSG channel to receive the out-of-band data. If the 
required client IDs are not listed in the DCD message, the DHCT will continue 
searching for out-of-band data. 
 
CMTS Global Configuration in a Non-Straddle Environment 
A "non-straddle environment" is defined as a single DOCSIS RF downstream that 
covers the DHCT populations that are served by the same hub. The system operator 
should configure the following criteria in a non-straddle environment: 
 
DSG tunnels with their respective MAC address 
 
DSG classifiers that allow the CMTS to route traffic to the appropriate DSG 
tunnel 
 
Client lists that are used by the DHCT to pick rules that apply to it 
 
CMTS Interface Configuration 
Each interface on the CMTS device that receives multicast traffic must have several 
customized configurations. These configurations must specifically address the 
following two scenarios for configuring the CMTS: 
 
Non-Hub Straddling (on page 10) 
 
Hub Straddling (Regionalization) (on page 14) 
The general IP multicast CMTS configurations include the following scenarios: 
 
Each interface that receives multicast traffic must be enabled with Protocol 
Independent Multicast (PIM). 
 
RF Interfaces that forward multicast traffic must be statically configured using 
the CMTS to join the Cisco out-of-band multicast groups defined on the DNCS.  
Note: Some Internetwork Operating Systems (IOS), for example, Cisco, 
automatically include the "ip igmp static" command when the "cable 
downstream DSG Rule" is configured. If this occurs for your CMTS, configuring 
the "ip igmp static" command will not be necessary. 
 
DSG Rules should be configured on the downstreams to which they apply. This 
will result in a different DCD message sent from each downstream. 
 
The configuration of a DSG "Classifier" is required. The DSG Classifier enables 
the DSG agent to map the IP multicast address to the DSG tunnel. If ports are not 
included in the DSG classifier or if the DSG classifier is not included in the DCD 
message, the set-top will filter the Cisco DSG data based on existing, well-known 
port numbers.