Configuring Headend Broadband Access Router Features
QoS Features
MC-526
Cisco IOS Multiservice Applications Configuration Guide
Multiple SIDs provide the following functionality:
• Voice traffic can be designated on a higher QoS committed information rate (CIR) secondary SID,
while data traffic can be forwarded on a best-effort basis on a primary SID.
• Secondary SIDs are higher QoS CIR-type classes to be used for higher priority traffic such as voice.
These classes have a nonzero minimum reserved rate (CIR-type service). Thus, these SIDs receive
preferential treatment at the headend for grants over any tiered best effort type data SID for that
upstream. Best-effort service involves requests with no minimum upstream rate on the channel.
The CMTS treats the primary and secondary SIDs independently for issuing grants. Each SID of a
cable modem has an independent state machine. Channel access for each SID is independent of the
other SID.
Note Reliable operation with voice requires multiple SIDs—at least two per
cable modem to separate voice from data traffic. In DOCSIS 1.0, SIDs are set
up statically. In DOCSIS 1.1, SIDs can be set up either statically or
dynamically.
QoS Profile Enforcement
QoS profile enforcement allows you to override the provisioned service class of a cable modem with a
static CMTS-defined QoS profile. A static CMTS-defined QoS profile gives you control of the cable
modem QoS and eliminates any interference from improper local-rate limiting implemented on the cable
modem.
When this feature is enabled, the CMTS provisions each registering cable modem with a default DOCSIS
1.0 service class that is assigned by the CMTS operator. The operator-defined service class is enforced
on cable modems attempting to register with the CMTS regardless of the provisioned class of service.
The default service class has no upstream or downstream rate limits.
When the cable modem sends data upstream, it makes bandwidth requests without throttling or dropping
packets because of its own rate-policing algorithm. The CMTS does traffic shaping based on the QoS
profile enforced by the operator.
Note By default, the system will not enforce a specific QoS profile on the cable modem. The QoS
profile assigned to the cable modem will depend on the class of service parameters
provisioned in the DOCSIS configuration file.
TAG/NetFlow Switching
TAG switching and Netflow switching provide high performance for network layer services, enabling
per-flow application of network services such as security and traffic accounting. The following data is
collected for each flow:
• Source and destination IP address
• Start of flow and end of flow timestamps
• Packet and byte counts
• Next hop router address
• Input and output physical port interfaces
