Interoperability With Different Versions Of Docsis Networks - Cisco cBR 8 Configuration Manual

DOCSIS 1.1 Quality of Service
DOCSIS 1.0+
In response to the limitations of DOCSIS 1.0 networks in handling real-time traffic, such as voice calls, Cisco
created the DOCSIS 1.0+ extensions to provide the more important QoS enhancements that were expected
in DOCSIS 1.1. In particular, the DOCSIS 1.0+ enhancements provide basic Voice-over-IP (VoIP) service
over the DOCSIS link.
Cisco's DOCSIS 1.0+ extensions include the following DOCSIS 1.1 features:
• Multiple SIDs per cable modem, creating separate service flows for voice and data traffic. This allows
the CMTS and cable modem to give higher priority for voice traffic, preventing the data traffic from
affecting the quality of the voice calls.
• Cable modem-initiated dynamic MAC messages—Dynamic Service Addition (DSA) and Dynamic
Service Deletion (DSD). These messages allow dynamic SIDs to be created and deleted on demand, so
that the bandwidth required for a voice call can be allocated at the time a call is placed and then freed
up for other uses when the call is over.
• Unsolicited grant service (CBR-scheduling) on the upstream—This helps provide a higher-quality
channel for upstream VoIP packets from an Integrated Telephony Cable Modem (ITCM) such as the
Cisco uBR925 cable access router.
• Ability to provide separate downstream rates for any given cable modem, based on the IP-precedence
value in the packet. This helps separate voice signaling and data traffic that goes to the same ITCM to
address rate shaping purposes.
• Concatenation allows a cable modem to send several packets in one large burst, instead of having to
make a separate grant request for each.
Caution All DOCSIS 1.0 extensions are available only when using a cable modem and CMTS that supports these
extensions. The cable modem activates the use of the extensions by sending a dynamic MAC message.
DOCSIS 1.0 cable modems continue to receive DOCSIS 1.0 treatment from the CMTS.

Interoperability with Different Versions of DOCSIS Networks

DOCSIS 1.1 cable modems have additional features and better performance than earlier DOCSIS 1.0 and
1.0+ models, but all three models can coexist in the same network. DOCSIS 1.0 and 1.0+ cable modems will
not hamper the performance of a DOCSIS 1.1 CMTS, nor will they interfere with operation of DOCSIS 1.1
features.
Table below shows the interoperability of a DOCSIS 1.1 CMTS with different versions of cable modems.
Table 8: DOCSIS 1.1 Interoperability
For this configuration...
DOCSIS 1.1 CMTS with DOCSIS 1.0 cable modems
Cisco cBR Series Converged Broadband Routers Quality of Services Configuration Guide for Cisco IOS XE
Fuji 16.7.x
42
DOCSIS 1.1 for the Cisco CMTS Routers
The result is...
DOCSIS 1.0 cable modems receive DOCSIS 1.0
features and capabilities. BPI is supported if available
and enabled on the CMTS.