Cisco cBR Series Hardware Installation Manual page 10

Functional Overview
The Cisco cBR runs on the Cisco IOS-XE networking software and supports the most advanced networking
and routing options.
Functional Overview
The Cisco cBR provides the following network solutions:
• High speed data access over DOCSIS
• Video over DOCSIS
• Voice services over DOCSIS
• Business services over DOCSIS
• MPEG transport-based video distribution
• Videoscape management system integration
• Data plane optimization to carry ABR traffic including monitoring of quality of service
• Assistance with the support of legacy devices in a Videoscape environment
• Video cache integration
The path from the Cisco CMTS to the cable modem or STB is the downstream, which carries the majority of
traffic over the cable interface.
The path from the cable modem or STB to the Cisco CMTS is the upstream, and it carries approximately 10
percent of the traffic that is sent over the downstream.
A large number of users can be assigned to the same downstream, and for efficient use of bandwidth, those
users can be split among several different upstream.
The following sections contain information about:
Upstream Data Path
The following example describes the upstream data path.
1. A request for service is generated by a subscriber. The modem transmits the request as a series of packets
to the Cisco CMTS on the upstream.
2. The cable line card receives the packets on its upstream interface and forwards them to its onboard
processor.
3. The line card processor verifies the header check sequence (HCS), frame check sequence (FCS), and
system identification number (SID), processes all fields in the DOCSIS MAC header, and then removes
the header.
1. The line card examines and processes the extended headers (Request, Acknowledgment, Privacy,
2. Bandwidth requests, acknowledgment (ACK) requests, and unsolicited grant syncs are reformatted
Cisco Converged Broadband Routers Hardware Installation Guide
2
PHSs and Unsolicited Grand Synchronization header elements). If Baseline Privacy Interface (BPI)
is used, the processor also decrypts the Privacy EH frames using the appropriate key.
and passed to the request ring of the Cisco cable line card.
What is a Cisco cBR Series Converged Broadband Router