Driven by market
evolution towards triple-play services, cable operators in emerging markets are
seeking standardized and digital fiber-based solutions for economical and
future proof access technologies. Much of the demand is driven by the need to
provide higher bandwidth packet transport for Internet connectivity, video and
Data Over Cable Systems Interface Standard (DOCSIS®) is a standardized
technology for services over cable and thus has strong interoperability between
system providers. It also provides robust Quality of Service (QoS) methods,
ensuring packet delivery during periods of network congestion. Traditionally,
DOCSIS runs on linear fiber (or HFC) to provide service and is not naturally
applicable for digital fiber. Cisco has bridged the gap by introducing a new
access technology called the Remote-PHY.
In the emerging
markets, most triple-play consumers live in multi-tenant buildings (referred to
as Multi Dwelling Units or MDU) with the number of residents usually being less
than 500 residents per building or cluster. These buildings are typically
served by fiber with one of several “final 100 meter” technologies installed in
the buildings. These technologies include fiber, twisted pair, Ethernet, and
coaxial. Cable operators have access to the cable in the building and use this
cable for their services. Several technologies exist for enabling two-way
services over cable. These include a number of proprietary and vendor-specific
methods. However, a standards-based approach to using cable is typically
preferred by operators, since this ensures vendor interoperability.
Need for the
Cisco Remote-PHY Solution
EuroDOCSIS are standards that define two-way operation over a cable network.
DOCSIS provides the necessary Quality of Service (QoS) tools for ensuring voice
call connectivity during periods of network congestion that are anticipated in
triple-play networks. DOCSIS is a robust and mature technology for voice,
video, and IP video services.
The Cisco Remote-PHY solution leverages existing IP technologies and deploys DOCSIS in remote field over digital fiber to enable two-way services over cable.
The Cisco Remote-PHY solution provides a cost-effective digital fiber-based DOCSIS solution that uses Metro Ethernet (MetroE) as the transmission network between the Cisco CMTS and the cable modem.
Reduced investment cost including capital and operational expenditure.
Low-cost yet highly stable Cisco GS7000 node (includes only the PHY layer).
Reduced CMTS hardware complexity.
No restriction on Converged Interconnect Network (CIN) network.
Futureproof architecture. Easy to migrate as the hardware and control functions are on separate layers.
End-to-end QoS assurance provided by DOCSIS.
Support for all DOCSIS services.
Support for existing DOCSIS network provisioning system.
High access bandwidth.
With deep fiber, the optical noise contribution to SNR is eliminated. As a result, the remote QAM modulator runs at higher orders of modulation as compared to a centralized QAM modulator.
Modular Headend Architecture version 2 (MHAv2) is a set of specifications for the Cisco Remote-PHY solution. It uses digital fiber compatible baseband networking technology to drive the fiber portion of the HFC plant. The coaxial portion of the plant remains the same. The upstream and downstream PHY are located on the remote side and acts as the remote PHY system. The Cisco GS7000 node with the Cisco DOCSIS R-PHY node acts as the remote PHY system. It connects the digital fiber and the coaxial portions of the plant together. The remote PHY system resides near or in buildings and has both RFI and Gigabit Ethernet interfaces. It provides layer 1 PHY (downstream and upstream PHY) functionality, layer 2 MAC functionality, and layer 3 tunneling and forwarding support. The CMTS remains unchanged with the exception of the upstream and downstream PHY being moved to the remote PHY system. The Cisco RF line card installed in the Cisco CMTS does not have the RFI interfaces for downstream and upstream, instead, it has Gigabit Ethernet interfaces for both downstream and upstream.
Protocols that form this architecture include:
Downstream External PHY Interface Decapsulation—Downstream External PHY Interface (DEPI) is a L2TPv3-based protocol defined for downstream DOCSIS MAC management and data packets decapsulation. It is unidirectional, that is, from CMTS to remote PHY system.
Upstream External PHY Interface Encapsulation—Upstream External PHY Interface (UEPI) is a L2TPv3-based protocol defined for upstream DOCSIS MAC management and data packets encapsulation. It is unidirectional, that is, from remote PHY system to CMTS.
Does not support UDP
Supports PSP mode only
Supports multiple pseudowires for RNG/BW-REQ/SPECTRUM-MGMT/MAP
GCP—Generic Control Protocol, sets up a control plane tunnel over a generic transport protocol such as TCP or UDP. GCP is used to program the remote PHY system upstream and downstream parameters from the CMTS. It is also used to control the remote PHY system.
DS/US PHY configuration and CMC provisioning/configuration
Register mode and type, length, value (TLV) mode
Cisco Cable Modem Termination System
The Cisco cBR converged broadband router acts as the Cable Modem Termination System (CMTS) core for the Cisco Remote-PHY architecture.
Following are its functions:
Assigns downstream and upstream channels of the Cisco RF line card to the Cisco DOCSIS R-PHY GS7000 node.
Performs MAC classification, forwarding, and management functions.
Handles the Cisco DOCSIS R-PHY GS7000 node configuration and management.
The Cisco 1.2 GHz Super High Output (SHO) GS7000 Node (Cisco GS7000 node) acts as the edge QAM in the Cisco Remote-PHY architecture. It is located between the Cisco CMTS and the cable modem, and controlled by the Cisco CMTS. The Cisco GS7000 node has network interfaces on one side connecting to the fiber (digital and linear) portion of the Hybrid Fiber Coaxial (HFC) plant, and RF interfaces on the other side connecting to the coaxial portion of the HFC plant. The Cisco GS7000 node can be mounted either on a wall or strand (aerial installation). The RF output of the Cisco GS7000 node can be combined with other services, such as, analog or digital video services. The Cisco GS7000 node uses the linux operating system. Most of the Cisco GS7000 node configurations are performed on the Cisco CMTS.
The Cisco GS7000 node originates the DOCSIS protocol using the DOCSIS MAC and PHY layer technology used in the Cisco CMTS. The Cisco GS7000 node has built-in downstream PHY and upstream PHY, and a small FPGA for DEPI decapsulation and UEPI encapsulation.
The Cisco Remote-PHY Device (RPD) resides inside the Cisco GS7000 node. Below are some of its features:
Full spectrum DOCSIS 3.0 support
Full spectrum DOCSIS 3.1 support
Converged broadcast, narrowcast, and VOD video support
Out of Band (OOB) signaling support
Dual 10GBE SFP+ backhaul connectivity
Support of Daisy Chain architecture topology
Support of optical overlay architectures
Figure 1. Cisco RPD
Cisco CCAP RF Line Card for R-PHY
The Cisco CCAP RF line card for remote PHY architecture is available in two flavours:
CBR-LC-8D31-16U30—This RF line card with the downstream and upstream PHY modules can be connected with the Cisco GS7000 node by configuring it using the card cBR-CCAP-LC-40G r-phy command.
CBR-CCAP-LC-40G-R—This RF line card with no downstream and upstream PHY modules can be connected with the Cisco GS7000 node.
Cisco Digital Physical Interface Card
The Cisco Digital Physical Interface Card (DPIC) transmits and receives RF signals between the subscriber and headend over the hybrid fiber-coaxial (HFC) system and is DOCSIS-compliant. This interface card is designed specifically for the Cisco cBR router and conforms to the Integrated CMTS (I-CMTS) architecture. The PID is cBR-DPIC-8X10G.
The DPIC is installed in the CMTS and connected to the Cisco GS7000 node via the Metro Ethernet. It supports both downstream and upstream traffic. Both the downstream and upstream traffic share the same ports.
Table 1 Physical Specifications of the DPIC
10.96 in (27.8cm)
1.43 in (3.6cm)
7.32 in (18.6cm) with handle
The DPIC supports:
Eight ten gigabit ethernet SFP+ interfaces
80 gigabit non-blocking switching architecture with 40+40 protection scheme
40 gigabit DOCSIS traffic bandwidth when connected with the Cisco CBR-CCAP-LC-40G-R line card
The faceplate of the Cisco DPIC has the following:
Optic Cable Clip—Helps route and manage the optic cables.
8 x SFP+ ports—Used as 8 x 10GE lanes for DOCSIS traffic to the Cisco RPDs.
10GE Link Status LED—Indicates the status of the 10GE link.
Status LED—Indicates the status of the Cisco DPIC.
Replace LED—Indicates the Cisco DPIC must be replaced.
Onboard Failure Logging
The Onboard Failure Logging (OBFL) feature enables the storage and collection of critical failure information in the nonvolatile memory of a Field Replaceable Unit (FRU), like a route processor (RP) or line card. The data stored through OBFL assists in understanding and debugging the field failures upon Return Material Authorization (RMA) of a RP or line card at repair and failure analysis sites. OBFL records operating temperatures, voltages, hardware uptime, and any other important events that assist board diagnosis in case of hardware failures.