Chapter 42: Fully-Qualified Domain Name (FQDN)
STANDARD Revision 1.0
C4® CMTS Release 8.3 User Guide
© 2016 ARRIS Enterprises LLC. All Rights Reserved.
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this feature enabled, the CMTSs in the network check the DNS server periodically using the provisioned FQDNs. If new
information is available, the CMTS automatically removes the prior multicast configuration and joins the multicast group
using the new source address. The end result is an automatic propagation of the new multicast configuration without
manual intervention except for entering the appropriate DNS record on the DNS server.
The C4 CMTS maintains the DNS server list and the default domain name list for all applications. The CMTS bases the
frequency of the DNS query messages on both the current Time-To-Live (TTL) value of the FQDN to IP binding and on the
poll interval setting. When the TTL expires, a query is sent by the CMTS to the DNS server to again resolve the FQDN.
Limited Support for FQDN Feature
Support for this feature is limited to the following applications:
DOCSIS Set-top Gateway (DSG) tunnel classifiers for pre-DOCSIS 3.0 Set-top boxes (STBs) on MDF-disabled MAC
domains.
Statically joined IGMPv3 (non-DSG) pre-DOCSIS 3.0 cable modems on MDF-disabled MAC domains.
Operational Concerns
This feature supports the association of an FQDN with only an IPv4 source address. Association with an IPv6 address is
not supported.
An FQDN cannot be used for the multicast destination or group.
The frequency of CMTS DNS queries is based on the Time-To-Live (TTL) value of the FQDN-to-IP binding.
This feature does not support IGMP static host joins. It supports only IGMP static router joins.
When the FQDN-to-IP binding changes, the C4 CMTS reestablishes only the affected DSG or IGMP statically provisioned
multicast groups. Forwarding packet counts in this case are cleared. These counts are not carried forward because they
are specific to the source/group addresses.
The C4 CMTS supports a maximum of 25 FQDN cache entries.
When the FQDN-to-IP binding changes, the Downstream Channel Descriptor (DCD) messages will be modified if they
include DSG tunnel classifiers. The classifiers will be modified to reflect the new IP address.