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Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide
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Chapter 1 Overview of Cisco uBR7200 Series Software
DOCSIS and CMTS Interoperability
Larger cable companies typically have high-speed fiber backbones that carry Internet data, voice, and
video between the following cable company facilities:
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Regional processing centers
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Headends
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Hubs
The fiber backbone can be made up of OC-3 (155 Mbps) to OC-48 (2488 Mbps) Synchronous Optical
Network (SONET) or Asynchronous Transfer Mode (ATM) rings. The backbone network can connect to
other networks, including the Public Switched Telephone Network (PSTN), other cable system
backbones, or to public Internet interconnect points that multiple ISPs use.
The CMTS Media Access Control (MAC) domain typically includes one or more downstream paths and
one or more upstream paths. Depending on the CMTS configuration, the CMTS MAC domain can be
defined to have its downstreams on one cable interface line card with its upstreams on another card, or
one or more CMTS MAC domains per cable interface line card.
Cisco provides high-speed routers to route interactive traffic between the backbone and Ethernet in the
headend internal network. Signaling protocols maintain the network intelligence needed to route traffic
optimally, automatically building and maintaining routing tables to direct traffic and signal failures for
rerouting in the network.
Border Gateway Protocol (BPG) typically operates between the cable operator’s regional network and
external networks, providing routing information exchange between different networks. The Open
Shortest Path First (OSPF) protocol is used in regional networks usually. Cisco routers incorporate Cisco
IOS software, which offers advanced software features, including quality of service (QoS), Weighted
Fair Queuing (WFQ), and IP multicast.
EuroDOCSIS Cable Plants
EuroDOCSIS-based cable plants use EuroDOCSIS J.112 (Annex A) standard, similar to the
DAVIC/DVB J.83 Annex A physical layer. The MC16E builds on the DOCSIS protocol, adding support
at the physical layer for PAL and SECAM channel plans. The card permits full bandwidth utilization of
the 8 MHz downstream channel, allowing up to 50 Mbps throughput, and greater upstream frequency
selection—5 to 65 MHz, instead of 5 to 42 MHz.
Figure 1-2
illustrates a three-tier EuroDOCSIS configuration involving STB deployment. The sample
architecture has four subsystems:
•
High-speed fiber backbone—Carries Internet data, voice, and video between regional processing
centers, headends, and hubs.
•
Headend—Aggregates content at the national and regional level and sends it to the fiber backbone.
•
Hub—Combines regional programming with local content and sends that combined content to the
cable network.
•
Interactive STBs with integrated EuroDOCSIS CMs—Connects subscribers to the cable network.
Video sources are Motion Picture Experts Group (MPEG) encoded and then fed into an MPEG multiplexer
that packs the MPEG video streams into a single stream. This stream is uplinked to a satellite and then
downlinked to multiple headends, which then distribute the MPEG stream directly onto the HFC plant.
The STB receives signals from the cable network and displays them on a television. An STB with
EuroDOCSIS cable modem functionality supports two-way interactivity. Inside the EuroDOCSIS STB are
two tuners:
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One handles MPEG-2 video, audio, broadcast control data, and broadcast service data.
•
The other supports DOCSIS IP data. The return path is implemented with EuroDOCSIS.
